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july 2010 doc id 12204 rev 10 1/20 20 stod2540 pmoled display power supply features inductor switches boost controller pfm mode control high efficiency over wide range of load (1 ma to 40 ma) integrated load disconnect switch over voltage protection with automatic restart soft start with adjustab le peak current limit enable pin low shutdown current small external inductor supply voltage from 3.0 v to 5.5 v application pmoled display driver description stod2540 is dedicated to passive matrix oled (pmoled) displays for portable handsets and provides the pre-charge and biasing voltage of the column matrix driver as shown in figure 3. the current capability of stod 2540 allows feeding a 1", 1.3" or 1.5" color pmoled. stod2540 is a boost converter that operates from 3.0 v to 5.5 v and can provide an output voltage as high as 25 v. the output current c apability is maximum 40 ma up to 25 v output voltage. the regulation is performed by a resistor divider network (figure 3) that detects the output voltage. in this state-of-the-art boost converter, a dc current path exists between the battery source and the load. in order to reduce the consumption in shutdown mode, a high-side load isolation switch is necessary to cut this dc current path in standby mode. the load disconnect switch (lds) act as an isolation switch in shutdown mode. qfn8 (3 x 3 mm) table 1. device summary order code package packaging STOD2540PUR qfn8 (3 x 3 mm) 3000 parts per reel www.st.com
contents stod2540 2/20 doc id 12204 rev 10 contents 1 diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3 maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4 electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 5.1 boost controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 5.2 adjustable peak inductor current limit . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 5.3 enable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 5.4 ovp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 5.5 load isolation switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 5.6 efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 5.7 under voltage lockout (uvlo) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 6 typical application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 6.1 demonstration board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 7 typical performance characteristi cs . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 8 package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 9 revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
stod2540 diagram doc id 12204 rev 10 3/20 1 diagram figure 1. block diagram
pin configuration stod2540 4/20 doc id 12204 rev 10 2 pin configuration figure 2. pin connections (top through view) table 2. pin description pin n symbol note 1v i supply voltage 2r set peak inductor current adjust 3 agnd analog ground 4 fb feedback for the led current regulation 5v o output voltage for led supply 6v cap load disconnect switch input 7 en ic enable signal 8v sw boost switch drain pgnd power ground
stod2540 maximum ratings doc id 12204 rev 10 5/20 3 maximum ratings table 3. absolute maximum ratings symbol parameter value unit vb sw , vb o breakdown voltage at out and sw pin 40 v v i supply voltage range 6 v r set r set pin v i + 0.3 v en enable pin v i + 0.3 v v esd esd ratings, hbm mil std 883c 2 kv t stg storage temperature range - 65 to 150 c t op operating junction temperature range - 40 to 85 c table 4. thermal data symbol parameter value unit r thja thermal resistance junction-ambient 52 c/w
electrical characteristics stod2540 6/20 doc id 12204 rev 10 4 electrical characteristics t j = 40 c to 85 c, v i = 3.6 v, v en = 3v, c i = c o = 4.7 f, l = 4.7 h, r 1 = 180 k , r 2 = 10 k , v o = 24 v, typ. values @ 25 c, unless otherwise specified. table 5. electrical characteristics symbol parameter test condition min. typ. max. unit v i input voltage range 3.0 5.5 v v o regulated output voltage v i = 3 v to 5.5 v v i + 0.5 25 35 v v ovp over voltage protection on output 35 v i o continuous output current v o = 25 v 140ma i sd stand-by current v en = low, v i = 3.6 v 3 a v en = low, v i = 3 v to 4.2 v 10 i q quiescent current consumption v i = 3 v to 4.2 v @ 25 c 0.4 0.8 ma v i = 5.5 v @ 25 c 0.8 1.2 r dson-sw boost switch r dson (1) v i = 4.2 v, i sw = 100 ma 0.4 bvds breakdown voltage 40 v r dson- lds r dson (1) v o = 25 v, i o = 30 ma 2 bvds breakdown voltage 40 v i lim-adj peak inductor limit range (1) r set = 10 k to 100 k 0.2 1.1 a i lim-max maximum peak inductor current (1) v i = 3 v to 5.5 v, r set = v i 0.75 1.2 a fb feedback voltage 5% @ 25 c 1.18 1.24 1.30 v t on_max maximum on time v i = 4.2 v 5.5 s t off_min minimum off time v i = 4.2 v 300 ns eff efficiency, v i = 3.6 v (1) i o = 1 ma to 5 ma 65 % i o = 5 ma to 40 ma 70 efficiency, v i = 4.2 v (1) i o = 1 ma to 5 ma 65 i o = 5 ma to 40 ma 70 ripple output ripple and noise v i = 3.6 v, i o = 5 ma, v o = 24 v 1.3 % v i = 3.6 v, i o = 30 ma, v o = 24 v 1.3 v i = 4.2 v, i o = 5 ma, v o = 24 v 1.3 v i = 4.2 v, i o = 30 ma, v o = 24 v 1.3 ov hyst over-voltage hysteresis 2 v
stod2540 electrical characteristics doc id 12204 rev 10 7/20 v en enable input logic low disable low v il 0.3 v enable input logic high enable high v ih 1.2 line_v fb line regulation v fb v i = 3 v to 5.5 v, i o = 5 ma 5 35 mv load_v fb line regulation v fb v i = 3 v to 5.5 v, i o = 5 ma 5 35 mv 1. guaranteed by design. table 5. electrical characteristics (continued) symbol parameter test condition min. typ. max. unit
functional description stod2540 8/20 doc id 12204 rev 10 5 functional description 5.1 boost controller stod2540 is a boost converter operating in pfm (pulsed frequency modulation) mode. the converter monitors the output voltage through the bridge resistor divider r 1 and r 2 and when the feedback voltage falls below the re ference voltage, ref2, the boost switch t sw turns on and the current ramps up. the inductor current is measured by detect the temperature compensated drain voltage of the boost mosfet. the boost turns off when its drain voltage reaches the reference ref1, the main switch remains off until the minimum off time (300 ns typical) has passed and the fee dback voltage is below the reference again. a maximum on time of 4 s prevent the switch t sw to stay on during a too long period of time. in order to well calculate the bridge resistors values with a fixed v o , the following formula can be used: (v o / 1.24) -1 = r 1 / r 2 5.2 adjustable peak inductor current limit the peak inductor current is monitored by sensing the drain voltage of the switch t sw . since it exceeds the temperature compensated and supply voltage compensated reference ref1, the rs flip flop is reset and t sw is turned off. by connecting a resistance between the pin r set and gnd, the peak current limit can be adjusted from 200 ma to 1.1 a (r set from 10 k to 100 k ). when the pin r set is directly connected to v i , the default value is 1 a. 5.3 enable the enable pin is a high logic input signal and allows turning on/off the controller without cutting the input voltage from the boost regulator circuit. with a high input voltage (1.2 v < v en < v i + 0.3 v) on this pin, the device is allowed to work normally. no pull-up or pull down is present on this pin. 5.4 ovp if the regulation loop is cut, there is no signal at the feedback pin, the pfm controller will then continue to switch without control and generate an output voltage at the sw, v cap and v o pin exceeding the breakdown value v bsw , v bcap and v bo . the over voltage protection (ovp) senses the voltage at the v cap pin. when the voltage exceed the breakdown voltage of the device the controller is automatically turned off. a hysteresis control enables the device to automatically restart when the output voltage drops below a 2 v typical value.
stod2540 functional description doc id 12204 rev 10 9/20 5.5 load isolation switch when the device is in shutdown mode, a dc current path always exists between the power source and the load; increasing the standby consumption. a high side switch lds isolates the load from the source when the stod2540 is disabled. 5.6 efficiency the total consumption of some pmoled display, can be as low as 1 ma. in order to increase the battery run time of the device, stod2540 offers a high efficiency over a wide range of load and input voltage range. 5.7 under voltage lockout (uvlo) the minimum supply voltage is 3.0 v, under this value the under voltage lockout circuit operates with typical threshold 2.8 v. when supply voltage is below 3.0 v, possible no ise in the supply line could disturb the uvlo circuit causing loss of output regulation . this behavior is eliminated choosing c i = 10 f or higher.
typical application stod2540 10/20 doc id 12204 rev 10 6 typical application note: the external components suggested in this document should be considered as a design reference guide. the performances mentioned in the electrical characteristics table are not guaranteed for all the possible electrical parameters of the components included in this list. on other hand, the operation of stod2540 is not limited to the use of components included in this list. figure 3. basic connection table 6. external components (see figure 3 ) symbol parameter test min. typ. max. unit d boost schottky diode vrrm 30 v v f at i f = 300 ma, t j = 25 c 0.5 v i r at v r = 10 v, t j = 25 c 30 a r 1 feedback resistor 180 k r 2 feedback resistor 10 r set peak current limit adjust i pk = 200 ma to 1.1 a 10 100 c i input ceramic type low esr ceramic type 4.7 f c o output capacitance: ceramic low esr capacitance 4.7 f voltage 42 v esr 1.6 w l boost inductor (height < 2mm) inductance 4.7 h i sat , r set pin to v i 1a
stod2540 typical application doc id 12204 rev 10 11/20 6.1 demonstration board figure 4. suggested demonstration board schematic (top layer view)
typical performance characteristics stod2540 12/20 doc id 12204 rev 10 7 typical performance characteristics t j = 40 c to 85 c, v i = 3.6 v, v en = 3 v, c i = c o = 4.7 f, l = 4.7 h, r 1 = 180 k , r 2 = 10 k , v o = 24 v, typ. values @ 25 c, unless otherwise specified. figure 5. efficiency vs. output current figure 6. efficiency vs. input voltage figure 7. v en vs. temperature figure 8. v fb vs. input voltage figure 9. v fb vs. output current figure 10. v fb vs. output current
stod2540 typical performance characteristics doc id 12204 rev 10 13/20 figure 11. v ovp vs. temperature figure 12. v ripple vs. input voltage figure 13. i lim_max vs. input voltage figure 14. i lim_max vs. temperature figure 15. i lim_max vs. r set figure 16. i q vs. temperature
typical performance characteristics stod2540 14/20 doc id 12204 rev 10 figure 17. t on_max vs. temperature figure 18. t off_min vs. temperature figure 19. line v fb vs. temperature figure 20. load v fb vs. temperature
stod2540 package mechanical data doc id 12204 rev 10 15/20 8 package mechanical data in order to meet environmental requirements, st offers these devices in different grades of ecopack ? packages, depending on their level of environmental compliance. ecopack ? specifications, grade definitions and product status are available at: www.st.com . ecopack ? is an st trademark. table 7. qfn8 (3 x 3 mm) mechanical data dim. mm. min. typ. max. a 0.800.901.00 a1 0 0.02 0.05 a3 0.20 b 0.250.300.35 d 2.853.003.15 d2 2.49 2.64 2.74 e 2.853.003.15 e2 1.75 1.90 2.00 e0.65 l 0.300.400.50
package mechanical data stod2540 16/20 doc id 12204 rev 10 figure 21. drawing dimension qfn8 (3 x 3 mm) 8057023_b
stod2540 package mechanical data doc id 12204 rev 10 17/20 dim. mm. inch. min. typ. max. min. typ. max. a1 8 0 7.0 8 7 c 12. 8 1 3 .2 0.504 0.51 9 d 20.2 0.7 9 5 n60 2. 3 62 t 14.4 0.567 ao 3 . 3 0.1 3 0 bo 3 . 3 0.1 3 0 ko 1.1 0.04 3 po 4 0.157 p 8 0. 3 15 tape & reel qfnxx/dfnxx ( 3 x 3 ) mechanical data
package mechanical data stod2540 18/20 doc id 12204 rev 10 figure 22. qfn8 (3x3) footprint recommended data
stod2540 revision history doc id 12204 rev 10 19/20 9 revision history table 8. document revision history date revision changes 22-mar-2006 1 initial release. 03-apr-2006 2 add fig. 2 demonstration board on page 3. 08-jun-2006 3 description in cover page updated. 23-jun-2006 4 change range of r set value and add description paragraph 5.7. 11-sep-2006 5 mistake on table 4 ripple test value 3.6 v ==> 4.2 v. 27-feb-2009 6 modified mechanical data. 03-mar-2009 7 modified packaging table1 on page1 . 11-mar-2009 8 modified figure 2 on page 4 and added figure 22 on page 18 . 25-nov-2009 9 modified table 1 on page 1 . 01-jul-2010 10 modified: table 7 on page 15 , figure 21 on page 16 and figure 22 on page 18 .
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