View MC34845BEPR2_1309676.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

document number: mc34845 rev. 5.0, 6/2010 freescale semiconductor advance information * this document contains certain information on a new product. specifications and information herein are subject to change without notice. ? freescale semiconductor, in c., 2010. all rights reserved. low cost 6 channel led backlight driver with integrated power supply the 34845 series represents high efficiency led drivers for use in backlighting lcd displays from 10? to 17? +. operating from supplies of 5.0 to 21v, the 34845 series is capable of driving up to 16 leds in series in 6 separate strings. the led current tolerance in the 6 strings is within 2% maximum and is set us ing a resistor to gnd. pwm dimming is performed by applying a pwm input signal to the pwm pin which modulates the led channels directly. an enable pin (en) provides for low power standby. alternatively, a single wire scheme selects power down when pwm is connected to the wake pin and held low. the integrated boost converter us es dynamic headroom control to automatically set t he output voltage. there ar e three device versions for boost frequency; 34845/c is 600 khz, 34845a is 1.2 mhz and the 34845b/d is 300 khz. external compens ation allows the use of different inductor/ capacitor combinations. the 34845 includes fault protection modes for led short and open, over temperature, over current and over voltage errors. it features an internally fixed ovp value of 60v (t ypical) which protects the device in the event of a failure in the extern ally programmed ovp. the ovp level can be set by using an external resistor divider. features ? input voltage of 5.0 to 21v ? boost output voltage up to 60v ?2.0 a integrated boost fet ? fixed boost frequency - 300 khz, 600 khz or 1.2 mhz ? otp, ocp, uvlo fault detection ? led short/open protection ? programmable led current between 3.0 ma and 30 ma ? 24-ld 4x4x0.65mm qfn package figure 1. 34845 simplified application diagram 34845 34845a/b/c/d led driver 98asa00087d 24-pin qfn-ep ordering information device temperature range (t a ) package mc34845ep/r2 -40 to 85c 24 qfn-ep mc34845aep/r2 mc34845bep/r2 mc34845cep/r2 mc34845dep/r2 12v fail pgndb 34845 swa swb vout pgnda ch1 ch2 ch3 ch4 ch5 ch6 ep en pwm iset vin vdc1 vdc2 comp wake ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ovp gnd gnd control unit 5v typical applications ? pc notebooks ? netbooks ? picture frames ? portable dvd players ? small screen televisions ? industrial displays ? medical displays
analog integrated circuit device data 2 freescale semiconductor 34845 device variations device variations table 1. device variations characteristic symbol min typ max unit boost switch current limit 34845, 34845a, 34845c 34845b, 34845d i boost_limit 1.9 2.1 2.1 2.35 2.3 2.6 a switching frequency 34845, 34845c 34845a 34845b, 34845d f s 540 1080 270 600 1200 300 660 1320 330 khz slope compensation 34845, 34845c 34845a 34845b, 34845d v slope - - - 0.52 0.73 0.22 - - - v/ s
analog integrated circuit device data freescale semiconductor 3 34845 internal block diagram internal block diagram figure 2. 34845 simplifi ed internal block diagram vin vdc1 comp en pwm iset swa swb pgndb fail ch1 ch2 ch3 ch4 ch5 ch6 6 channel boost logic controller current mirror v sense gnd pgnda ldo vdc2 vout bandgap circuit wake low power mode
analog integrated circuit device data 4 freescale semiconductor 34845 electrical characteristics absolute maximum ratings electrical characteristics absolute maximum ratings table 2. absolute maximum ratings all voltages are with respect to ground unless otherwise no ted. exceeding these ratings may cause a malfunction or permanent damage to the device. ratings symbol value unit electrical ratings maximum pin voltages swa, swb, vout ch1, ch2, ch3, ch4, ch5, ch6 (off state) ch1, ch2, ch3, ch4, ch5, ch6 (on state) fail, ovp comp, iset pwm, wake en, vin v max -0.3 to 65 -0.3 to 45 -0.3 to 20 -0.3 to 7.0 -0.3 to 2.7 -0.3 to 5.5 -0.3 to 24 v maximum led current per channel i led_max 33 ma esd voltage (1) human body model (hbm) machine model (mm) v esd 2000 200 v thermal ratings operating ambient temperature range t a -40 to 85 c maximum junction temperature t j 150 c storage temperature range t s -40 to 150 c peak package reflow temperature during reflow (2) , (3) t pprt note 3 c thermal resistance junction to ambient (4) t ja 36 c/w thermal resistance junction to case (5) t jc 3.1 c/w power dissipation (4) ta = 25c ta = 85c p d 3.4 1.8 w notes 1. esd testing is performed in accordance with the human body model (hbm) (aec-q100-2) (c zap = 100 pf, r zap = 1500 ), and the machine model (mm) (c zap = 200 pf, r zap = 0 . 2. pin soldering temperature limit is for 10 seconds maximum du ration. not designed for immersion soldering. exceeding these lim its may cause malfunction or permanent damage to the device. 3. freescale?s package reflow capability me ets pb-free requirements for jedec standard j-std-020c. for peak package reflow temperature and moisture sensitivity levels (m sl), go to www.freescale.com, search by part number [e.g. remove prefixes/suffixe s and enter the core id to view all orderable parts. (i.e. mc33xxxd enter 33x xx), and review parametrics. 4. per jedec51-8 standard for multilayer pcb 5. theoretical thermal resistance is fr om the die junction to the exposed pad.
analog integrated circuit device data freescale semiconductor 5 34845 electrical ch aracteristics static and dynamic elec trical characteristics static and dynamic electrical characteristics table 3. static and dynamic el ectrical characteristics characteristics noted under conditions v in = 12 v, v out = 35 v, i led = 30 ma, f s = 600 khz, f pwm = 600 hz - 40 c t a 85 c, unless otherwise noted. typical values not ed reflect the approximate parameter means at t a = 25c under nominal conditions, unless otherwise noted. characteristic symbol min typ max unit supply supply voltage v in 5.0 10 21 v supply current when in shutdown mode en = low, pwm = low i shutdown - 2.0 10 a supply current when operational mode boost = pulse skipping, c hannels = 1% of duty cycle en = high, pwm = low i operational - 5.0 6.5 ma under-voltage lockout v in rising uvlo 4.0 - 4.4 v under-voltage hysteresis v in falling uvlo hyst - 0.25 - v vdc1 voltage (6) c vdc1 = 2.2 f v dc1 2.4 2.5 2.6 v vdc2 voltage (6) (v in between 7.0 and 21 v) c vd2c = 2.2 f v dc2 5.7 6.0 6.3 v boost output voltage range (7) vin = 5.0 v vin = 21 v v out1 v out2 8.0 24 - - 43 60 v boost switch current limit 34845, 34845a, 34845c 34845b, 34845d i boost_limit 1.9 2.1 2.1 2.35 2.3 2.6 a boost switch current limit timeout t boost_time - 10 - ms rdson of internal fet i drain = 1.0 a r dson - 300 520 m boost switch off state leakage current v swa,swb = 60 v i boost_leak - - 1.0 a feedback pin off-state leakage current v out = 60 v vout leak - - 500 a peak boost efficiency (8) v out = 33 v, rl = 330 eff boost - 90 - % notes 6. this output is for internal use only and not to be used for other purposes 7. minimum and maximum output voltages are dependent on min/max duty cycle condition. 8. boost efficiency test is perform ed under the following conditions: f sw = 600 khz, v in = 12 v, v out = 33 v and r l = 330 . the following external components are used: l = 10 h dcr = 0.1 , c out = 3x1 f (ceramic), schottky diode v f = 0.35 v.
analog integrated circuit device data 6 freescale semiconductor 34845 electrical characteristics static and dynamic electrical characteristics boost (continued) line regulation v in = 7.0 v to 21 v, i ch = 30 ma i led /v in -0.2 - 0.2 %/v load regulation v led = 24 v to 40 v (all channels), i ch = 30 ma i led /v led -0.2 - 0.2 %/v minimum duty cycle d min - 10 15 % maximum duty cycle d max 88 90 - % ovp internally fixed value (no external voltage resistor divider) v ovp_int 56 60 64 v ovp programming range (9) (set through an external resistor divider) v ovp_ext 15 - 60 v ovp reference voltage v ref_ovp 6.3 6.9 7.5 v ovp sink current i sink_ovp - 0.2 - a switching frequency 34845, 34845c 34845a 34845b, 34845d f s 540 1080 270 600 1200 300 660 1320 330 khz soft start time (fs=600 khz, 100% pwm duty) t ss - 3.0 - ms soft start vout overshoot (fs=600 khz, 100% pwm duty) ss_ vout - - ovp v boost switch rise time boost_t r - 8.0 - ns boost switch fall time boost_t f - 6.0 - ns current sense amplifier gain a csa - 9.0 - ota transconductance g m - 200 - s transconductance sink and source current capability i ss - 100 - a slope compensation 34845, 34845c 34845a 34945b, 34845d v slope - - - 0.52 0.73 0.22 - - - v/ s led driver led driver sink current r iset = 51 k 0.1%, pwm = 3.3 v r iset = 5.1 k 0.1%, pwm = 3.3 v i led 2.88 29.4 3.0 30 3.12 30.6 ma iset pin voltage r iset = 5.1 k 0.1% v iset 2.011 2.043 2.074 v regulated minimum voltage across led drivers pulse width > 400ns v min 0.675 0.75 0.825 v led current channel to channel tolerance 10 ma i led 30 ma 3.0 ma i led < 10 ma i tolerance -2.0 -4.0 - - 2.0 4.0 % notes 9. the ovp level must be set 5.0 v above the worst-case led string voltage. table 3. static and dynamic elect rical characteristics (continued) characteristics noted under conditions v in = 12 v, v out = 35 v, i led = 30 ma, f s = 600 khz, f pwm = 600 hz - 40 c t a 85 c, unless otherwise noted. typical values note d reflect the approximate parameter means at t a = 25c under nominal conditions, unless otherwise noted. characteristic symbol min typ max unit
analog integrated circuit device data freescale semiconductor 7 34845 electrical ch aracteristics static and dynamic elec trical characteristics led driver (continued) off state leakage current, all channels v ch = 45 v i ch_leak - - 1.0 a led channels rise and fall time t r /t f - 50 75 ns led open protection, channel disabled if v ch o fdv o fdv - - 0.55 v led short protection voltage, channel disabled if v ch s fdv (channel on time 10 s) s fdv 6.5 7.0 7.5 v fail pin off state leakage current v fail = 5.5 v i fail_leak - - 5.0 a on state voltage drop i sink = 4.0 ma v ol - - 0.4 v over-temperature shutdown over-temperature threshold (shutdown mode) rising hysteresis ott shutdown 150 - 165 25 - - c pwm input pwm dimming mode led current control pwm = 3.3 v, f pwm = 600 hz 10% duty; pwm = 3.3 v, f pwm = 600 hz 50% duty pwm = 3.3 v, f pwm = 600 hz 100% duty pwm control 9.9 49.5 - 10 50 100 10.1 50.5 - % input minimum pulse pwm pin (v pwm =3.3 v) start-up (wake mode) operational (wake mode) start-up (enable mode) operational (enable mode) t pwm_in 1.6 - 0.4 - - 0.2 - 0.2 - - - - s input frequency range for pwm pin f pwm dc - 100 khz wake shutdown mode timeout t shutdown 27 30 33 ms logic inputs (pwm) input low voltage v ill -0.3 - 0.5 v input high voltage v ihl 1.5 - 5.5 v input current i sink -1.0 - 1.0 a logic inputs (en) input low voltage v ill -0.3 - 0.5 v input high voltage v ihl 2.1 - 21 v input current (v en = 12 v) i sink - 6.0 10 a logic inputs (wake) input low voltage v ill -0.3 - 0.5 v input high voltage v ihl 2.1 - 5.5 v input current i sink -1.0 - 1.0 a table 3. static and dynamic elec trical characteristics (continued) characteristics noted under conditions v in = 12 v, v out = 35 v, i led = 30 ma, f s = 600 khz, f pwm = 600 hz - 40 c t a 85 c, unless otherwise noted. typical values not ed reflect the approximate parameter means at t a = 25c under nominal conditions, unless otherwise noted. characteristic symbol min typ max unit
analog integrated circuit device data 8 freescale semiconductor 34845 pin connections static and dynamic electrical characteristics pin connections figure 3. 34845 pin connections table 4. 34845 pin definitions pin number pin name definition 1 vin main voltage supply input. ic power input supply voltage, is used in ternally to produce internal voltage regulation for logic functioning, and also as an input voltage for the boost regulator. 2 pgndb power ground. this is the ground terminal for the internal boost fet. 3 swb boost switch node connection b. switching node of boost converter. 4 swa boost switch node connection a. switching node of boost converter. 5 pgnda power ground. this is the ground terminal for the internal boost fet. 6 en enable pin (active high, internal pull-down). 7 - 12 ch1 - ch6 led string connections 1 to 6. led current drivers. each line has the capabili ty of driving up to 30 ma. 13, 19, 21 gnd ground reference for all internal circuits other than the boost fet. the exposed pad (ep) should be used for thermal heat dissipation. 14 fail fault detected pin (open drain): no failure = low-impedance pull-down failure = high-impedance when a fault situation is detected, this pin goes into high impedance. 15 iset led current setting. the maximum current is se t using a resistor from this pin to gnd. 16 pwm external pwm control signal. 17 comp boost compensation component connection. this passive term inal is used to compens ate the boost converter. add a capacitor and a resistor in series to gnd to stabilize the system as we ll as a shunt capacitor. 18 wake low power consumption mode for single wire control. this is achieved by connecting the wake and pwm pins together and grounding the enable (en) pin. 20 vdc1 2.5 v internal voltage decoupling. this pi n is for internal use only, and not to be used for other purposes. a capacitor of 2.2 f should be connected between this pin and ground. 22 ovp external boost over-voltage setting. r equires a resistor divider from vout to gnd. if no external ovp setting is desired, this pin should be grounded. 23 vdc2 6.0 v internal voltage decoupling. this pi n is for internal use only, and not to be used for other purposes. a capacitor of 2.2 f should be connected between this pin and ground. 24 vout boost voltage output feedback. ep ep ground and thermal enhancement pad vin pgndb swb swa pgnda gnd en wake iset fail vout vdc2 ovp comp vdc1 gnd gnd pwm ch1 ch2 ch3 ch4 ch5 ch6 24 17 18 19 20 21 22 23 1 8 7 6 5 4 3 2 16 9101112 13 14 15 ep gnd transparent top view
analog integrated circuit device data freescale semiconductor 9 34845 functional description introduction functional description introduction led backlighting has been popular for use in small lcd displays for many years. this technology is now rapidly replacing the incumbent cold cathode fluorescent lamp (ccfl) in mid-size displays such as those used use in notebooks, monitors and industri al/ consumer displays. leds offer a number of advantages compared to the ccfl, including lower power, thinner, longer lifetime, low voltage drive, accurate wide-range dimming control and advanced architectures for improved image quality. leds are also void of hazardous materi als such as mercury which is used in ccfl. led backlights use different architecture depending on the size of the display and features required. for displays in the 10? to 17? + range such as those used in notebooks, edge-lit backlights offer very thin designs down to 2mm or less. the efficiency of the led backlight also extends battery life in portable equipment compared to ccfl. in large size panels, direct backlights support advan ced architectures such as local dimming, in which power consumption and contrast ratio are drastically improved. edge lighting can also be used in large displays when low cost is the driving factor. the 34845 targets mid size panel applications in the 10? to 17? + range with edge-lit backlights. the device supports led currents up to 30ma and supports up to 6 strings of leds. this enables backlights up to 10w to be driven from a single device. the device includes a boost converter to deliver the required led voltage from either a 2 or 3 cell li-ion battery, or a direct 12v input supply. the current drivers match the current between devices to provide superior uniformity across the display. the 34845 provides for a wide range of pwm dimming from a direct pwm control input. functional device operation power supply the 34845 supports 5.0v to 21v at the vin input pin. two internal regulators generate internal rails for internal operation. both rails are de-coupled using capacitors on the vdc1 and vdc2 pins. the vin, vdc1, and vdc2 supplies each have their own uvlo mechanisms. when any voltage is below the uvlo threshold, the device stops ope rating. all uvlo comparators have hysteresis to ensure constant on/off cycling does not occur. the power up sequence for applying vin respect to the enable and pwm signals is important since the 34845 device will behave differently depending on how the sequence of these signals is applied. for the case where vin is applied before the enable and pwm signals, the device will have no limitation in terms of how fast the vin ramp should be. however for the case where the pwm and enable signals are applied before vin, the ramp up time of vin between 0v and 5v should be no longer than 2ms. figures 4 and 5 illustrate the two different power up conditions. figure 4. power up sequence case 1, vin applied before the enable and pwm signals. no limitation for vin ramp up time. vin en pwm vout boost soft st ar t
analog integrated circuit device data 10 freescale semiconductor 34845 functional device operation introduction figure 5. power up sequence case 2, vin applied after the enable and pwm signal s. vin ramp up time between 0v and 5v should be not higher than 2ms boost converter the boost converter uses a dynamic headroom control (dhc) loop to automatically set the output voltage needed to drive the led strings. the dhc is designed to operate under specific pulse width conditions in the led drivers. it operates for pulse widths higher than 400 ns. if the pulse widths are shorter than specified, the dhc circuit will not operate and the voltage across the led drivers will increase to a value given by the ovp, minus the total led voltage in the led string. it is therefore imperative to select the proper ovp level to avoid exceeding the max off state voltage of the led drivers (45v). the boost operates in current mode and is compensated externally through a type 2 network on the comp pin. a modification of the compensation network is suggested to minimize the amplitude of the ripple at v out . the details of the suggested compensation network are shown in figures 10 and 11 . an integrated 2.0a minimu m fet supplies the required output current. an over -current protection circuit limits the output current cycle-by-cycle to i ocp . if the condition exists longer than 10 ms, then the device will shut down. the frequency of the boost converter is internally set to 300 khz, 600 khz or 1.2 mhz, depending on the device?s version. the boost also includes a soft start circuit. each time the ic comes out of shutdown mode, the soft start period lasts for t ss . over-voltage protection is also included. the device has an internally fixed ovp value of 60v (typical) which serves as a secondary fault protection mechanism, in the event the externally programmed ovp fails (i.e. resistor divider opens up). while the internal 60v ovp detector can be used exclusively without the external ovp network, this is only recommended for applications where the led string voltage approaches 55 v or more. the ovp level can be set by using an external resistor divider connected between the output voltage and ground with its outpu t connected to the ovp pin. the ovp can be set up to 60v by varying the resistor divider to match the ovp internal reference of 6.9v (typical). led driver the 6 channel led driver provides current matching for 6 led strings to within 2% maximum. the current in the strings is set using a resistor ti ed to gnd from the iset pin. the led current level is given by the equation: rset = 153/ iled. the accuracy of the rset resistor should be 0.1% for best performance. led error detect if an led is open, the output voltage ramps to the ovp level. if there is still no current in the led string, the led channel is turned off and the out put voltage ramps back down to normal operating level. if leds are shorted and the voltage in any of the channels is greater than the sfdv threshold (7.0 v typical), then the device will turn off that channel. however if the on-time of the channels is less than 10 s, the sfdv circuit will not disable any of the channels, regardless of the voltage across them. all the led errors can be cleared by recycling the en pin or applying a complete power-on-reset (por). wake operation the wake pin provides the me ans to set the device for low power consumption (shutdow n mode) without the need of an extra logic signal for enable. this is achieved by connecting the wake a nd pwm pins togethe r, and tying the en pin to ground. in this configuration, the pwm signal is used to control the led channels, while allowing low power consumption by setting the device into its shutdown mode every time the pwm signal is kept low for longer time than the wake time out of 27 ms. over-temperature shutdown and temperature control circuits the 34845 includes over-temper ature protection. if the internal temperature exceed s the over-temp threshold ott shutdown , then the device shuts down all functions. once the temperature falls belo w the low level threshold, the device is re-enabled. fail pin the fail pin is at its low-impedance state when no error is detected. however, if an error such as an led channel open or boost over-current is de tected, the fail pin goes into high-impedance. once a failure is detected, the fail pin can be cleared by recycling the en pin or applying a complete power-on-reset (por). if the detected failure is an over- current time-out, the en pi n or a por must be cycled/ executed to restart the part. vin en pwm vout bo ost soft start 5v 2ms vin ramp uvlo rising
analog integrated circuit device data freescale semiconductor 11 34845 typical performance curves introduction typical performance curves figure 6. typical system effi ciency vs duty cycle (fpwm=25khz) figure 7. typical iled dimming linearity (fpwm=25khz) 0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 0 102030405060708090100 duty cycle (%) efficiency (%) vin=9v fs = 600khz l=10uh, 68mohm (ihlp2525cze r100m01) schottky 5a, 100v (pds5100hdict-nd) cout = 2x2.2f fpwm=25khz load = 9 leds, 20ma/channel vled = 27.8v, 0.5v /channel chablis iled dimming linearity (fpwm=25khz) -2.000% -1.500% -1.000% -0.500% 0. 000% 0. 500% 1. 000% 1. 500% 2. 000% 110100 % duty cycle % iled channel mismatch (-) mismatch @ 25c (+) mis matc h @ 25c chablis iled dimming linearity (fpwm=25khz) -2.000% -1.500% -1.000% -0.500% 0. 000% 0. 500% 1. 000% 1. 500% 2. 000% 110100 % duty cycle % iled channel mismatch (-) mismatch @ 25c (+) mis matc h @ 25c
analog integrated circuit device data 12 freescale semiconductor 34845 typical performance curves introduction figure 8. typical operating waveforms (fpwm=25khz, 50% duty) figure 9. low duty dimming operation waveforms (fpwm=25 khz, 1% duty) pwm vout (ac coupled) vch1 iled1 pwm vout (ac coupled) vch1 iled1 pwm vout (ac coupled) vch1 iled1 pwm vout (ac coupled) vch1 iled1
analog integrated circuit device data freescale semiconductor 13 34845 typical applications introduction typical applications figure 10. typical application circuit for single wire control, f s = 600 khz (v in = 9.0v, i led /channel = 20 ma/channel, 10 leds/channel, ovp = 35v, v pwm = 3.3v) mc 3484 5 ch5 ch1 ch2 ch3 33 uh ch4 20 23 18 11 10 9 8 7 3 4 60 v, 1a le d le g 2 vi n le d le g 1 ch6 12 le d le g 3 sw a sw b le d le g 4 le d le g 5 le d le g 6 4.7 uf ovp 14 fail 22 1 vin 2.2uf 10 v vd c 1 2. 2uf 10 v vd c 2 en 6 24 vo u t pg n d 2 5 pg n d wake ep 10uf 25v 15 0.1 % 21 13 gnd gnd pwm 16 680k 167k 4.7 uf 100 pf 100pf 100 pf 100 pf 100 pf 100p f 0. 1uf 220pf com p 17 33nf ko 10k cont rol un it 3.3k /c 765k caps should be located as close as possible to the mc34845 device 7.65k
analog integrated circuit device data 14 freescale semiconductor 34845 typical applications introduction figure 11. typical application circuit for single wire control, f s = 1.2 mhz (v in = 9.0v, i led = 20 ma/channel, 10 leds/channel, ovp = 35v, v pwm = 3.3v) figure 12. typical application circuit for single wire control, f s = 300 khz (v in = 8.0v, i led = 20 ma/channel, 14 leds/channel, ovp = 49v, v pwm = 3.3v) mc34845a ch5 ch1 ch2 ch3 10uh ch4 20 23 18 11 10 9 8 7 3 4 60 v, 1a le d le g 2 vi n le d le g 1 ch6 12 le d le g 3 sw a sw b le d le g 4 le d le g 5 le d le g 6 2.2 uf ovp 14 fail 22 1 vin 2.2nf 10 v vd c 1 2. 2uf 10 v vd c 2 en 6 24 vo u t pg n d 2 5 pg n d wake ep 10uf 25v 15 0.1 % 21 13 gnd gnd pwm 16 mo 2.2uf 100 pf 100pf 100 pf 100 pf 100 pf 100p f 0. 1uf 56pf com p 17 7nf 3.3k ko cont rol un it 10k 167k 680k 765k caps should be located as close as possible to the mc34845 device 7.65k mc 34845 b/d ch5 ch1 ch2 ch3 33 u h ch4 20 23 18 11 10 9 8 7 3 4 80 v, 1a led leg 2 vin le d le g 1 ch6 12 le d le g 3 swa swb led leg 4 led leg 5 led leg 6 ovp 14 fail 22 1 vi n 2.2uf 10v vd c1 2.2uf 10 v vd c2 en 6 24 vout pgnd 2 5 pgnd wake ep 10 u f 25 v 15 0. 1 % 21 13 gnd gnd pw m 16 100 pf 10 0 pf 10 0 pf 100 pf 10 0 pf 100 pf 0. 1 uf 220pf comp 56nf 2k co nt ro l unit 2uf 10k 114k 680k 2uf 2uf 2uf 765k caps should be located as close as possible to the mc34845 device 7.65k
analog integrated circuit device data freescale semiconductor 15 34845 typical applications components calculation components calculation the following formulas are intended for the calculation of all external components relat ed with the boost converter and network compensation. in order to calculate the duty cycle, the internal losses of the mosfet and diode should be taken into consideration: the average input current depe nds directly on the output current when the internal switch is off. inductor for calculating the inductor, consider the losses of the internal switch and winding resistance of the inductor: it is important to look for an inductor rated at least for the maximum input current: input capacitor the input capacitor should handle at least the following rms current. output capacitor for the output capacitor se lection the transconductance should be taken in consideration. the output voltage ripple ( v out ) depends on the esr of the output capacitor. for a low output voltage ripple, it is recommended to use ceramic capacitors that have a very low esr. since ceramic capacitor ar e costly, electrolytic or tantalum capacitors can be mi xed with ceramic capacitors for a less expensive solution. the output capacitor should at least handle the following rms current. network compensation since this boost converter is current controlled, a type ii compensation is needed. note that before calculating the network compensation, all boost converter components need to be known. for this type of compensation it is recommended to push out the right half plane zero to higher frequencies where it will not significantly affect the overall loop. the crossover frequency must be set much lower than the location of the right half plane zero: since our system has a fixed slope compensation, r comp should be fixed for all configurations, i.e. r comp = 2 kohm c comp1 and c comp2 should be calculated as follows: the recommended values of these capacitors for an acceptable performanc e of the system in different operating conditions are ccomp1=33nf and ccomp2=220pf. in order to improve the transient response of the boost a resistor network can be impl emented from the pwm pin to ground with a connection to the compensation network. this configuration should inject a 1v signal to the comp pin and the equivalent thevenin resistance of the divider should be close to r comp , (i.e. for 2k comp resistor, r comp = 3.3k and r shunt = 10k. see figure 10 , figure 11 and figure 12 for implementation guidelines. if a faster transient response is needed, a higher voltage (e.g. 1.3v) should be injected to the comp pin; so the resistor divider should be modified accordingly but keeping the equivalent thevenin resistance of the divider close to r comp . d v out v d v in ? + v out v d v sw ? + ---------------------------------------------- - = i in avg ? i out 1d ? ------------ - = l v in v sw ?i in avg ? r inductor () ? () d i in avg ? r f sw ----------------------------------------------------------------------------------------------------------------- - = i in max ? i in avg ? v in v out v in ? () 2l f sw v out --------------------------------------------------------- + = i rms c in ? v in v out v in ? () 2l f sw v out --------------------------------------------------------- ?? ?? ?? 0.3 = c out r comp 5 g m i out l 1d ? () v out 0.35 ------------------------------------------------------------------------------- = esr c out v out v out f sw l v out 1d ? () -------------------------------------------------------------------------- - = i rms c out ? i out d 1d ? ------------ - = f rhpz v out 1d ? () 2 i out 2 l --------------------------------------------- = f cross f rhpz 5 -------------- - = c comp1 2 f cross comp r ------------------------------------------------------------ - = c comp2 2 g m 6.28 f sw ----------------------------- =
analog integrated circuit device data 16 freescale semiconductor 34845 typical applications components calculation variable definition d = duty cycle v out = output voltage v d = diode voltage v in = input voltage v sw = internal switch voltage drop. v out = output voltage ripple i in-avg = average input current = i l-avg i out = output current i in-max = maximum input current r = current ripple ratio at the inductor = i l / i l-avg i rms-cin = rms current for the input capacitor i rms-cout = rms current for output capacitor l = inductor. r inductor = inductor winding resistor f sw = boost switching frequency c out = output capacitor r comp = compensation resistor g m = ota transconductance esr cout = esr of the output capacitor f rhpz = right half plane zero frequency f cross = crossover frequency c comp1 = compensation capacitor c comp2 = shunt compensation capacitor component suggestions the component sugestions only apply to t he conditions shown. therefore, adjustments are necessary for different application conditions. table 5. component suggestion table application case vin(min) vin(max) vo(max) vovp fboost iled per channel rovp_upper rovp_lower l(min) l(min) continuous mode cin(min) cout(min) rcomp at v pwm=3.3v rshunt at v pwm=3.3v ccomp1 ccomp2 1 9v 12v 30v 35v 600khz 20ma 680kohm 167kohm 22uh 33uh 1x10uf; x7r; 25v 2 x 4.7uf; x7r; 50v 3.3kohm 10kohm 33nf 220pf 2 6v 12v 43v 48v 300khz 23ma 680kohm 114kohm 22uh 33uh 1x10uf; x7r; 25v 4 x 2.2uf; x7r; 100v 2kohm 16kohm 56nf 220pf isat min = 2.6a
analog integrated circuit device data freescale semiconductor 17 34845 packaging package dimensions packaging package dimensions for the most current package revision, visit www.freescale.com and perform a keyword search using the ?98a? listed below. ep suffix 24-pin 98asa00087d revision a
analog integrated circuit device data 18 freescale semiconductor 34845 packaging package dimensions ep suffix 24-pin 98asa00087d revision a
analog integrated circuit device data freescale semiconductor 19 34845 packaging ep suffix 24-pin 98asa00087d revision a
how to reach us: home page: www.freescale.com web support: http://www.freescale.com/support usa/europe or locations not listed: freescale semiconductor, inc. technical information center, el516 2100 east elliot road tempe, arizona 85284 1-800-521-6274 or +1-480-768-2130 www.freescale.com/support europe, middle east, and africa: freescale halbleiter deutschland gmbh technical information center schatzbogen 7 81829 muenchen, germany +44 1296 380 456 (english) +46 8 52200080 (english) +49 89 92103 559 (german) +33 1 69 35 48 48 (french) www.freescale.com/support japan: freescale semiconductor japan ltd. headquarters arco tower 15f 1-8-1, shimo-meguro, meguro-ku, tokyo 153-0064 japan 0120 191014 or +81 3 5437 9125 support.japan@freescale.com asia/pacific: freescale semiconductor china ltd. exchange building 23f no. 118 jianguo road chaoyang district beijing 100022 china +86 10 5879 8000 support.asia@freescale.com for literature requests only: freescale semiconductor literature distribution center p.o. box 5405 denver, colorado 80217 1-800-441-2447 or +1-303-675-2140 fax: +1-303-675-2150 ldcforfreescalesemiconductor@hibbertgroup.com freescale? and the freescale logo are trademarks of freescale semiconductor, inc. all other product or service names are the property of their respective owners. ? freescale semiconductor, inc. 2010. all rights reserved. mc34845 rev. 5.0 6/2010 information in this document is provided solely to enable system and software implementers to use freescale semiconductor products. there are no express or implied copyright licenses granted hereunder to design or fabricate any integrated circuits or integrated circuits based on the information in this document. freescale semiconductor reserves the right to make changes without further notice to any products herein. freescale semiconductor makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does freescale semiconductor assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation consequential or incidental damages. ?typical? parameters that may be provided in freescale semiconductor data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. all operating parameters, including ?typicals?, must be validated for each customer application by customer?s technical ex perts. freescale semiconductor does not convey any license under its patent rights nor the rights of others. freescale semiconductor products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications intended to support or sustain life, or for any other application in which the failure of the freescale semiconductor product could create a situation where personal injury or death may occur. should buyer purchase or use freescale semiconductor products for any such unintended or unauthorized application, buyer shall indemnify and hold freescale semiconductor and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that freescale semiconductor was negligent regarding the design or manufacture of the part.

▲Up To Search▲

Price & Availability of MC34845BEPR2

	To Download MC34845BEPR2 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .