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????????????????????????????????????????????????????????????????? maxim integrated products 1 general description the max16948 is a dual high-voltage, current-sensing low dropout linear regulator (ldo)/switch designed to operate with an input voltage range from 4.5v to 28v (45v load dump tolerant). the device provides phantom power over coax cable to remote radio frequency low-noise amplifiers (lnas) in automotive systems with a maximum current of 300ma per channel. the device also provides a fixed regu - lated output voltage of 8.5v or an adjustable 1v to 12.5v out - put voltage. the device can also be configured as a switch. the device monitors the load current and provides an ana - log output current proportional to the sensed load current. accurate internal current limits pro tect the input supply against both overcurrent and short-circuit conditions. the device features an open-drain error output for each channel to indicate to the microcontroller ( f c) when a fault has occurred. the device features short-to-battery protection to latch off the internal ldo/switch during a short-to-battery event. during a thermal overload, the device reduces power dissipa tion by going into thermal shutdown. it includes two independent active-low, high-voltage-compatible shutdown inputs to place each channel in a low-power shutdown mode. the device is available in a 16-pin tqfn package with exposed pad, a 16-pin qsop package with exposed pad, or a 16-pin qsop package and is fully specified over the -40 n c to +105 n c temperature range. features s 2-channel ldo/switch with precision-adjustable current-sense (up to 300ma per channel) s wide input voltage range: 4.5v to 28v (45v load dump tolerant) s on/off switching or regulation of phantom power under c control s reverse current protection s output short-to-battery protection s load current monitoring to detect open-load/ normal/short-circuit conditions s open-drain error status signaling to c s input overvoltage shutdown s high power-supply rejection ratio (73db) applications remote lna phantom power automotive camera and sensor power typical operating circuits 19-6054; rev 1; 4/12 ordering information appears at end of data sheet. for related parts and recommended products to use with this part, refer to www.maxim-ic.com/max16948.related . max16948 fb1 err1 lim1 r1 1 r2 1 r pu1 r pu2 r load1 c out1 d out1 c in2 c sense1 c in1 d in c reg battery input c supply error flags current-sense outputs to adc c load1 r lim2 c lim1 l out1 l load1 cable 1 out1 in gnd sense1 r sense1 c sense2 r sense2 sense2 err2 shdn1 off on shdn2 reg fb2 lim2 r1 2 r2 2 r load2 c out2 d out2 c load2 r lim2 c lim2 l out2 l load2 cable 2 out2 typical operating circuits continued at end of data sheet. max16948 automotive dual remote antenna current-sense ldo/switch evaluation kit available for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxims website at www.maxim-ic.com.
????????????????????????????????????????????????????????????????? maxim integrated products 2 max16948 automotive dual remote antenna current-sense ldo/switch (all voltages referenced to gnd.) in, shdn1 , shdn2 ............................................... -0.3v to +45v err1 , err2 , reg ............................................... -0.3v to +6.0v fb1, fb2, sense1, sense2, lim1, lim2 .. -0.3v to (v reg + 0.3v) out1, out2 .......................................................... -0.3v to +20v continuous power dissipation (t a = +70 n c) tqfn-ep (derate 25.0mw/ n c above +70 n c) ............ 2000mw qsop-ep (derate 22.7mw/ n c above +70 n c) ........... 1818mw qsop (derate 9.5mw/ n c above +70 n c) ..................... 762mw operating temperature range ....................... -40 n c to +105 n c storage temperature range ........................... -65 n c to +150 n c junction temperature ..................................................... +150 n c lead temperature (soldering, 10s) ................................ +300 n c soldering temperature (reflow) ...................................... +260 n c tqfn-ep junction-to-ambient thermal resistance ( b ja ) .......... 40 n c/w junction-to-case thermal resistance ( b jc ) ................. 6 n c/w 16 qsop-ep junction-to-ambient thermal resistance ( b ja ) .......... 44 n c/w junction-to-case thermal resistance ( b jc ) ................. 6 n c/w 16 qsop junction-to-ambient thermal resistance ( b ja ) ........ 105 n c/w junction-to-case thermal resistance ( b jc ) ............... 37 n c/w absolute maximum ratings note 1: package thermal resistances were obtained using the method described in jedec specification jesd51-7, using a four- layer board. for detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial . stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. these are stress ratings only, and functional opera - tion of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. package thermal characteristics (note 1) electrical characteristics (v in = 14v, t a = t j = -40 n c to +105 n c, unless otherwise noted. typical values are at t a = t j = +25 n c.) (note 2) parameter symbol conditions min typ max units power switch/ldo in operating supply range v in over 19v, output and current sense is switched off (note 3) 4.5 28 v output switched off, for < 1s (note 3) 45 in supply current in operation i in v shdn1 / shdn2 > 2.8v, t a = +25 n c 2.1 3.4 ma in supply current in shutdown i sd shdn1 = shdn2 = gnd, t a = +25 n c, v in = 12v 7 f a in undervoltage lockout v uvl v in rising 4.8 v v in falling 3.8 4.45 in undervoltage lockout hysteresis v uvl-hys 390 mv voltage drop of internal switch v in - v out1/out2 measured between in and out1/out2, i out1/out2 = 100ma, fb1/fb2 = gnd, sw operation v in r 5v, t a = +105 n c (note 4) 0.3v v measured between in and out1/out2, i out1/out2 = 100ma, fb1/fb2 = gnd, sw operation v in r 5v, t a = +25 n c 0.145 0.220 feedback voltage v fb for ldo mode with external resistive dividers, i out1/out2_ = 5ma to 150ma 0.97 1 1.03 v
????????????????????????????????????????????????????????????????? maxim integrated products 3 max16948 automotive dual remote antenna current-sense ldo/switch electrical characteristics (continued) (v in = 14v, t a = t j = -40 n c to +105 n c, unless otherwise noted. typical values are at t a = t j = +25 n c.) (note 2) parameter symbol conditions min typ max units input bias current to fb1 and fb2 i fb1/fb2 v fb1/fb2 = 1.0v, ldo mode, t a = +25 n c -0.5 +0.5 f a feedback threshold for internal feedback resistive divider v fb1/fb2,th switching to ldo mode with internal 8.5v resistive dividers v reg - 1.7 v reg - 0.8 v adjustable output voltage range v out1/out2 ldo mode with external resistive dividers (notes 3, 5) 1 12.5 v fb1 and fb2 load regulation d v fb, load v in - v out1/out2 r 2v, i out1/out2 = 5ma to 250ma, ldo mode (note 3) -7 mv fb1 and fb2 line regulation d v fb, line v in - v out1/out2 r 2v, i out1/out2 = 50ma, ldo mode (note 3) 100 f v/v fixed output voltage 8.5v v out1/out2, 8.5v i out1/out2 = 70ma, ldo mode with internal resistive divider, 9v < v in < 18v 8.33 8.5 8.67 v power-supply rejection ratio psrr v in - v out1/out2 r 2v, i out1/out2 = 10ma at f = 100hz, ldo mode v out1/out2 = 8.5v, v ripple = 0.5v p-p (note 3) 73 db current sense sense1 to out1 and sense2 to out2 current ratio a i v sense1/sense2 < 3v i out1/out2 = 100ma, v in = 5v, 19v 0.485 0.5 0.515 % 50ma p i out1/out2 p 300ma, v in r 5v (note 3) 0.45 0.5 0.55 20ma p i out1/out2 p 50ma, v in r 5v (note 3) 0.415 0.5 0.585 5ma p i out1/out2 p 20ma, v in r 5v (note 3) 0.325 0.5 0.675 sense1, sense2, lim1, lim2 leakage current i leak shdn1 = shdn2 = gnd, t a =+ 25 n c 2 f a failure detection lim1 and lim2 current-limit threshold voltage v lim1/lim2,th voltage on lim1 and lim2 for which output current is limited 2.375 2.5 2.625 v in overvoltage lockout threshold (rising) v ovlo,r v in rising 19 21 23 v in overvoltage lockout threshold (falling) v ovlo,f v in falling 18.5 v in overvoltage lockout hysteresis v ovlo,h 600 mv
????????????????????????????????????????????????????????????????? maxim integrated products 4 max16948 automotive dual remote antenna current-sense ldo/switch electrical characteristics (continued) (v in = 14v, t a = t j = -40 n c to +105 n c, unless otherwise noted. typical values are at t a = t j = +25 n c.) (note 2) note 2: devices are tested at t a = +25 n c and guaranteed by design for t a = t min to t max . note 3: guaranteed by design; not production tested. note 4: guaranteed by ate characterization. limits are not production tested. note 5: in case of out1/out2 shorted to bat, feedback network must protect fb1/fb2 from violating their absolute maximum rat - ings. for out1/out2 set below 3.3v, use an additional 5v clamp on fb1/fb2 with low parasitic capacitance. parameter symbol conditions min typ max units short-to-bat threshold in off state v s2b v out1/out2 - v in , checked during turn- on sequence -500 -80 +110 mv reverse current detection level i revcur power fet on (sw or ldo mode) -100 -50 -1 ma reverse current (short-to-bat) shutdown delay t pd-rc delay to shutdown the switch or ldo after drop over r on becomes negative, i out1/out2 = -200ma (typ), t a = +25 n c 4.16 20 f s reverse current blanking time t blk-rc blanking time for reverse current and fb1/fb2 out of range after rising edge of shdn1 , shdn2 , or current limiting event is over 16 ms feedback voltage out of range v fberr ldo mode, internal pulldown resistor switched on, fb rising 1.12 1.15 1.28 v feedback voltage out-of- range hysteresis v fberr-hys ldo mode, internal pulldown resistor switched on (note 3) 39 100 mv overtemperature protection (note 3) thermal shutdown t shdn 160 n c thermal shutdown hysteresis t shdn-hys 15 n c supporting circuits, interface signals internal voltage regulator v reg t a = +25 n c, i reg = 0ma, v in = 4.5v to 18v 4 5 5.5 v t a = +25 n c, i reg = 0ma, v in = 6.5v to 18v 4.5 5 5.5 v internal voltage regulator current limit i reg (note 4) 15 ma err1 and err2 output- voltage low v ol sinking current = 10ma 0.4 v err1 and err2 open-drain leakage current err1 and err2 not asserted, v err1 / err2 = 5v, t a = +25 n c 1 f a shdn1 and shdn2 high v shdn1 / shdn2 ,hi 2.8 v shdn1 and shdn2 low v shdn1 / shdn2 ,lo 0.8 v shdn1 and shdn2 pulldown resistance r shdn v shdn1 / shdn2 = 2v 500 k i startup response time t st shdn1 and shdn2 rising to turn on ldo/switch (note 3) 300 f s out pulldown resistor r out1/out2-off shdn1 = shdn2 = gnd 56 k i
????????????????????????????????????????????????????????????????? maxim integrated products 5 typical operating characteristics (v in = 14v, t a = +25 n c, see the typical operating circuits , unless otherwise noted.) power-supply rejection ratio vs. frequency max16948 toc06 frequency (khz) psrr (db) 100 1 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 -100 0.01 10,000 v out_ = 5v fb_ = external resistive divider v ripple_ = 0.5v p-p i out_ = 10ma voltage drop of internal switch vs. supply voltage max16948 toc05 supply voltage (v) v in - v out (mv) 15 10 5 7.1 7.2 7.3 7.4 7.5 7.6 7.7 7.8 7.9 8.0 7.0 02 0 fb_ = gnd i out_ = 5ma out1 out2 dropout voltage vs. output current max16948 toc04 output current (ma) dropout voltage (mv) 250 200 150 100 50 100 200 300 400 500 600 700 0 0 300 t a = +105 c t a = +25c t a = -40c fb_ = reg dropout voltage vs. output current max16948 toc03 output current (ma) dropout voltage (mv) 250 200 150 100 50 100 200 300 400 500 600 700 0 0 300 v out = 5v fb_ = external t a = +105 c t a = +25c t a = -40c voltage drop of internal switch vs. output current max16948 toc02 output current (ma) v in - v out (mv) 250 200 150 100 50 100 200 300 400 500 600 700 0 0 300 fb_ = gnd t a = +105 c t a = +25 c t a = -40c shutdown current vs. temperature max16948 toc01 temperature (c) shutdown current (a) 80 55 30 5 -20 4.5 5.0 5.5 6.0 6.5 7.0 4.0 -45 105 shdn1 = shdn2 = gnd max16948 automotive dual remote antenna current-sense ldo/switch
????????????????????????????????????????????????????????????????? maxim integrated products 6 typical operating characteristics (continued) (v in = 14v, t a = +25 n c, see the typical operating circuits , unless otherwise noted.) current-sense amplifier gain vs. temperature max16948 toc12 temperature (c) current-sense amplifier gain (%) 80 55 30 5 -20 0.494 0.496 0.498 0.500 0.502 0.504 0.492 -45 105 fb_ = gnd i out_ = 100ma sense2 sense1 startup waveform (fb_ = gnd, i out_ = 90ma) max16948 toc11 200s/div v shdn1 and v shdn2 5v/div v out1 10v/div v out2 10v/div startup waveform (fb_ = reg, i out_ = 90ma) max16948 toc10 100s/div v shdn1 and v shdn2 5v/div v out1 5v/div v out2 5v/div power-up waveform (fb_ = gnd, i out_ = 90ma) max16948 toc09 200s/div v in 10v/div v out1 10v/div v out2 10v/div power-up waveform (fb_ = reg, i out_ = 90ma) max16948 toc08 100s/div v in 10v/div v out1 5v/div v out2 5v/div power-supply rejection ratio vs. frequency max16948 toc07 frequency (khz) psrr (db) 100 1 -80 -70 -60 -50 -40 -30 -20 -10 0 -90 0.01 10,000 fb_ = reg v ripple_ = 0.5v p-p i out_ = 10ma max16948 automotive dual remote antenna current-sense ldo/switch
????????????????????????????????????????????????????????????????? maxim integrated products 7 typical operating characteristics (continued) (v in = 14v, t a = +25 n c, see the typical operating circuits , unless otherwise noted.) line transient (v out_ = 5v, i out_ = 50ma) max16948 toc18 1ms/div v in 10v/div 18v 10v v out1 (ac-coupled) 10mv/div v out2 (ac-coupled) 10mv/div line transient (fb_ = reg, i out_ = 50ma) max16948 toc17 1ms/div v in 10v/div 18v 10v v out1 (ac-coupled) 10mv/div v out2 (ac-coupled) 10mv/div v reg vs. i reg max16948 toc16 i reg (ma) v reg (v) 30 20 10 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 1.0 04 0 v sense_ vs. r sense_ max16948 toc15 r sense_ (k ) v sense_ (v) 3 2 1 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 0 04 fb_ = gnd i out_ = 300ma current-sense amplifier error vs. output current max16948 toc14 output current (ma) current-sense amplifier error (%) 250 200 150 100 50 -1.4 -1.2 -1.0 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 -1.6 0 300 fb = gnd sense2 sense1 current-sense amplifier gain vs. output current max16948 toc13 output current (ma) current-sense amplifier gain (%) 250 200 150 100 50 0.493 0.494 0.495 0.496 0.497 0.498 0.499 0.500 0.501 0.502 0.503 0.492 0 300 fb = gnd sense2 sense1 max16948 automotive dual remote antenna current-sense ldo/switch
????????????????????????????????????????????????????????????????? maxim integrated products 8 max16948 automotive dual remote antenna current-sense ldo/switch pin configurations pin descriptions pin name function qsop/ qsop-ep tqfn-ep 1 15 n.c. no connection. not internally connected. 2 16 out1 ldo/switch output 1 to remote load. bypass out1 to gnd with >1 f f in parallel with 100nf low-esr ceramic capacitors for regulator stability. 3 1 shdn1 active-low shutdown input for out1. shdn1 is pulled to gnd with an internal 500k i resistor. 4 2 in input voltage. bypass in to gnd with an electrolytic capacitor with a minimum value of 10 f f and a low-esr ceramic capacitor with a minimum value of 0.1 f f. 5 3 shdn2 active-low shutdown input for out2. shdn2 is pulled to gnd with an internal 500k i resistor. 6 4 out2 ldo/switch output 2 to remote load. bypass out2 to gnd with >1 f f in parallel with 100nf low-esr ceramic capacitors for regulator stability. 7 5 gnd ground 8 6 reg internal 5v regulator. provides supply for internal low-voltage blocks, sense_, and lim_ outputs. 9 7 fb2 feedback input for setting the out2 voltage. connect fb2 to gnd to select current-limited switch operation. connect to an external resistive divider for adjustable output-voltage operation. connect fb2 to reg to choose the internal resistive divider for the 8.5v regulator option. *ep *ep *connect ep to gnd. sense1 err1 in 1 2 16 15 fb1 lim1 out1 shdn1 n.c. qsop-ep/qsop top view 3 4 14 13 sense2 lim2 gnd 51 2 err2 shdn2 out2 6 7 11 10 fb2 reg 89 + 15 16 14 13 6 5 7 in out2 8 shdn1 err1 sense2 sense1 12 fb1 4 12 11 9 n.c. out1 lim2 fb2 reg gnd + shdn2 err2 3 10 lim1 tqfn (4mm 4mm) top view max16948 max16948
????????????????????????????????????????????????????????????????? maxim integrated products 9 max16948 automotive dual remote antenna current-sense ldo/switch pin descriptions (continued) pin name function qsop/ qsop-ep tqfn-ep 10 8 lim2 output of current sense for limiting. this output is proportional to current flowing through out2. the internal current-limit amplifier is tripped when the voltage on lim2 reaches 2.5v. connect a resistor to gnd to set the level for current limitation and a 0.1 f f capacitor in par - allel for frequency compensation of the current-limit loop. 11 9 sense2 output of current sense for sensing. the current of sense2 is proportional to the current flowing through out2. connect a resistor from sense2 to gnd to set the output voltage level. additionally, connect a 0.1 f f capacitor from sense2 to gnd. 12 10 err2 open-drain fault indicator output 2 13 11 err1 open-drain fault indicator output 1 14 12 sense1 output of current sense for sensing. the current of sense1 is proportional to the current flowing through out1. connect a resistor from sense1 to gnd to set the output voltage level. additionally, connect a 0.1 f f capacitor from sense1 to gnd. 15 13 lim1 output of current sense for limiting. this output is proportional to current flowing through out1. the internal current-limit amplifier is tripped when the voltage on lim1 reaches 2.5v. connect a resistor to gnd to set the level for current limitation and a 0.1 f f capacitor in par - allel for frequency compensation of the current-limit loop. 16 14 fb1 feedback input for setting the out1 voltage. connect fb1 to gnd to select current-limited switch operation. connect to an external resistive divider for adjustable output-voltage operation. connect fb1 to reg to choose the internal resistive divider for the 8.5v regulator option. ep exposed pad (max16948a only). connect ep to the ground plane for optimal heat dissipa - tion. do not use ep as the primary electrical ground connection.
???????????????????????????????????????????????????????????????? maxim integrated products 10 max16948 automotive dual remote antenna current-sense ldo/switch functional diagram detailed description the max16948 is a dual high-voltage, current-sensing ldo/switch designed to operate with an input voltage range from 4.5v to 28v (45v load dump tolerant). the device provides phantom power over coax cable to remote radio frequency low-noise amplifiers (lnas) in automotive systems with a maximum current of 300ma per channel. the device also provides a fixed regulated output voltage of 8.5v, an adjustable 1v to 12.5v output voltage, or the device can be configured as a switch. the device is ideal for providing phantom power to remote radio-frequency lnas in automotive applications. the device monitors the load current, and its current- sense outputs provide a current proportional to the sensed load current. an accurate programmable current limit pro tects the input supply against both overcur - rent and short-circuit conditions. the device features open-drain fault indicator outputs and overtemperature shutdown. the device features short-to-battery protection to latch off the internal ldo/switch during a short-to-battery event. during a thermal overload, the device reduces power dissipa tion by going into thermal shutdown. it includes dual independent, active-low, high-voltage-compatible shutdown inputs to place each channel in a low-power shutdown mode. max16948 i-sense charge pump ref i-lim (2.5v) fb (1.0v) out1/ out2 in fb1/ fb2 err1 current limit reverse i 2x in 21v control ref, reg temperature sensor current sources diagnostics out > in fb > 1.2v err2 out_ > in_ fb_ > 110% reg lim1/ lim2 sense1 sense2 gnd shdn1 shdn2
???????????????????????????????????????????????????????????????? maxim integrated products 11 max16948 automotive dual remote antenna current-sense ldo/switch fault detection the device monitors the load current through an internal sense resistor to protect against short-circuit, short-to- battery, and reverse current faults. in addition, the device also detects input and output overvoltage conditions and features thermal shutdown. short circuit and overcurrent the current limit of each channel is programmed with an external resistor connected to the output of the cur - rent sense amplifiers lim_ to protect the device during short-circuit or overcurrent conditions. when the voltage at lim_ reaches the internal 2.5v threshold, the output current of the ldo/switch is limited, and err_ asserts low but the output is not disabled. the err_ and lim_ outputs should be monitored by the f c, and the channel experiencing the short-circuit or overcurrent condition should be disabled by pulling shdn_ low. if this condi - tion persists, thermal shutdown could occur and both outputs could be disabled. short-to-battery and reverse current detection it is possible for out_ to be shorted to the battery due to a fault in the system. each channel detects this failure by comparing the voltage at out_ and in before the switch turns on. every time the ldo/switch is enabled on the rising edge of shdn_ or during the exiting of thermal shutdown, the short-to-battery detec tion is performed. at this point, if the device detects the short-to-battery fault, the ldo/switch stays off and err_ is asserted low. the fault is latched, and the startup resumes when the short- to-battery fault is removed and shdn_ is toggled. during normal operation if a short-to-battery fault results in reverse current for more than 5 f s (typ) the ldo/switch is latched off and err_ is asserted low. to remove the latched condition after a short-to-battery (reverse current) fault, the fault condition must first be removed and shdn_ must be toggled. series inductance and the output capacitor can produce ringing during large load transients when enabling the ldo/switch, resulting in an output voltage that temporarily exceeds the input volt age. blanking is implemented during startup. the reverse current blank ing time (t rev_blank ) is 16ms (typ). when the max16948 is operated with input voltage close to the output voltage, as in switch mode operation or ldo mode in dropout, care must be taken to avoid a false reverse current detection in the presence of a short circuit to ground fault. if both channels are enabled and one chan - nel is shorted to ground after startup, the current drawn from c in may result in a temporary dip in the intput voltage, which may trigger the reverse current detection fault. to aovoid this false trigger event, use an electrolytic capacitor of at least 100 f f. thermal shutdown thermal shutdown circuitry protects the device from overheating. the switch turns off immediately when the junction temperature exceeds +160 n c (typ). the switch turns on again after the device tempera ture drops by approximately 15 n c (typ). fb inputs (fb1/fb2) fb1 and fb2 control the output voltage on out1 and out2. connect fb_ to gnd to select current-limited switch operation. connect to an external resistive divider for adjustable output voltage operation (feedback volt - age 1v (typ)). connect fb_ to reg to choose the internal resistive divider for the 8.5v regulator option. table 1. fault response device status v lim? (v) v err ldo/sw output latched normal operation 0 p v lim_ < 2.5 high enabled no short circuit to gnd or overcurrent 2.5 low enabled no v out > v in at startup 0 low disabled yes reverse current 0 low disabled yes v fb > 1.2v 0 high enabled no input overvoltage 0 low disabled no thermal shutdown 0 high disabled no
???????????????????????????????????????????????????????????????? maxim integrated products 12 max16948 automotive dual remote antenna current-sense ldo/switch undervoltage and overvoltage lockout the device includes undervoltage lockout circuitry (uvlo) to prevent erroneous switch operation when the input voltage goes below 4.45v (max) during startup and brownout conditions. input voltages of less than 4.45v inhibit operation of the device by turning off the internal charge pump and the switch. the device also features an overvoltage lockout (ovlo) threshold of +21v (typ). when v in is greater than v ovlo, the device immediately turns off the switch and the inter - nal charge pump. shutdown ( shdn1 , shdn2 ) the device features two active-low shut down inputs ( shdn1 , shdn2 ) to place the device in a low-power shutdown mode. shdn1 controls out1 and shdn2 controls out2. the device turns off both channels and consumes a maximum of 7 f a (at v in = 12v) of shutdown current when both shdn1 and shdn2 are low. driving shdn1 and/or shdn2 high initiates device turn-on with short-to-battery detection. shdn1 and shdn2 are pulled to gnd with an internal 500k i resistor. internal voltage regulator (reg) the device features an internal regulator that regulates the input voltage to +5v to power all inter nal circuitry. bypass the regulator output (reg) to gnd with a 1 f f ceramic capacitor. the reg output can be used to sup - ply external circuitry up to a maximum 15ma current. applications information/external component selection fixed/adjustable output voltage the device is configurable to provide a fixed 8.5v output or as an adjustable ldo with an output between 1v and 12.5v. connect fb_ to reg to configure the device as an 8.5v ldo. connect a resistive divider between out_, fb_, and gnd to set the output to the desired voltage. fb_ is regulated to 1.0v with q 3% accuracy for a load current between 5ma and 150ma. select a value for r2 and calculate r1 as follows: out_ fb_ v r1 1 r2 v ?? = ? ?? ?? ?? where r2 must be less than or equal to 1k i . select r1 and r2 such that the maximum input bias current at fb (0.5 f a) is negligible compared to the current flowing through r1 and r2. current-limit resistor and capacitor selection the current-sense outputs at lim1/lim2 are proportional to the load current at out1/out2 and are internally con - nected to a current-limit comparator referenced to 2.5v. the desired current limit is set with an external resistor r lim_ using the following equation: lim_ load_max(a) 2.5(v) r () 0.5% i ?= a 0.1 f f compensation capacitor c lim_ must be placed in parallel with r lim_ to establish a dominant pole in the current limiting loop to maintain stability and to prevent fast current transients from prematurely triggering the current limit. current-sense resistor selection the current-sense outputs sense1/sense2 are pro - portional to the load current at out1/out2. an output resistor r sense _ must be connected between sense1/ sense2 and gnd to generate a current-sense voltage prior to sampling by an adc. r sense is calculated using the following equation: a d c,f s sense_ load_max(a) v (v) r () 0.5% i ?= where v adc,fs is the full-scale input voltage of the adc. a 0.1 f f capacitor c sense should be placed in parallel with r sense to hold the voltage during adc sampling cycles. in addition to adc sampling, open-load or overcurrent conditions can be detected by using external comparators and splitting r sense_ into a resistive divider as shown in figure 1 . in this circuit the outputs of comparators u1 and figure 1. open-load and overcurrent detection circuit max16948 r3 sense_ r5 r4 v oc,th v oc v ol u1 u2 v ol,th
???????????????????????????????????????????????????????????????? maxim integrated products 13 max16948 automotive dual remote antenna current-sense ldo/switch u2 indicate the operating state of the circuit as shown in table 2 . the open-load and overcurrent limits are set using the following equations: ol,th open load(a) v (v) r5( ) 0.5% i ? ?= where v ol,th is the open-load voltage threshold for comparator u2 and i open-load is the desired open-load threshold for the current flowing through the ldo/switch. oc,th overcurrent(a) v (v) r4( ) r5 0.5% i ?= ? where v oc,th is the overcurrent voltage threshold for comparator u1. i overcurrent is the desired overcur - rent threshold for the current flowing through the ldo/ switch and the internal current limit should be pro - grammed such that i load_max > i overcurrent . r3( ? ) = r sense_ - r4 - r5 the open-load voltage threshold v ol,th and overcurrent threshold v oc,th can be generated from reg utilizing a resistive divider. the thresholds should be selected such that v oc,th > v ol,th . input capacitor connect a parallel electrolytic capacitor and a low-esr ceramic capacitor from in to gnd to limit the input- voltage drop during momentary output short-circuit con - ditions and to protect the device against transients due to inductance on the in line. for example, use at least a 0.1 f f ceramic capacitor in parallel with a 10 f f electro - lytic capactior if the input inductance (including any stray inductance) is estimated to be 20 f h. larger capacitor values reduce the voltage undershoot and overshoot in case of reverse current. output capacitor connect >1 f f in parallel with 0.1 f f low-esr ceramic capacitors between out1/out2 and gnd for regulator stability. these capacitors should be placed as close to the device as possible. utilize capacitors with an x7r dielectric to ensure stability over the operating tempera - ture range of the device. in an analogous fashion to the input capacitor, an output capacitor protects the device against transients due to any series inductance in the output. under no condi tions should the voltage on out1/out2 go below -0.3v as specified in the absolute maximum ratings section. a schottky diode is required as a clamp if transients are expected to go below ground. table 2. open-load and overcurrent- detection circuit states oc ol state 0 0 normal operation 0 1 open-load condition 1 0 overcurrent condition 1 1 invalid state
???????????????????????????????????????????????????????????????? maxim integrated products 14 max16948 automotive dual remote antenna current-sense ldo/switch ordering information /v denotes an automotive qualified part. + denotes a lead(pb)-free/rohs-compliant package. * future productcontact factory for availability. ** ep = exposed pad. typical operating circuits (continued) max16948 fb1 err1 lim1 2.7k 2.7k r load1 1f 0.1f 1f 0.1f 10f battery input c supply error flags current-sens e outputs to ad c c load1 2.5k 0.1f 1mh l load1 cable 1 out1 in reg gnd sense1 4k 0.1f 4k sense2 err2 shdn1 off on shdn2 fb2 lim2 3k 750 r load2 1f c load2 2.5k 0.1f 1mh l load2 cable 2 out2 chip information process: bicmos package information for the latest package outline information and land patterns (footprints), go to www.maxim-ic.com/packages . note that a +, #, or - in the package code indicates rohs status only. package drawings may show a different suffix character, but the drawing pertains to the package regardless of rohs status. part temp range pin-package max16948agte/v+ -40 n c to +105 n c 16 tqfn-ep** max16948agee/v+ -40 n c to +105 n c 16 qsop-ep** max16948bgee/v+* -40 n c to +105 n c 16 qsop package type package code outline no. land pattern no. 16 tqfn-ep t1644+4 21-0139 90-0070 16 qsop-ep e16e+9 21-0112 90-0240 16 qsop e16+5 21-0055 90-0167
maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circuit patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 15 ? 2012 maxim integrated products maxim is a registered trademark of maxim integrated products, inc. revision history revision number revision date description pages changed 0 9/11 initial release 1 4/12 updated maximum output voltage 1, 3, 10, 12 max16948 automotive dual remote antenna current-sense ldo/switch

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