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september 2006 rev. 5 1/19 19 STOD2540 pmoled display power supply feature summary inductor switcher boost controller. pfm mode control. high efficiency over wide range of load (1ma to 40ma). integrated load disconnect switch. over voltage protection with automatic restart soft start with adjustable peak current limit enable pin low shutdown current. small external inductor. supply voltage from 3.0v to 5.5v 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 STOD2540 allows feeding a 1", 1.3" or 1.5" color pmoled. STOD2540 is a boost converter that operates from 3.0v to 5.5v and can provide an output voltage as high as 25v. the output current capability is maximum 40ma up to 25v 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) actsas an isolation switch in shutdown mode. qfn8 (3mm x 3mm) www.st.com order codes part number package packaging STOD2540pmr qfn8 (3mm x 3mm) 4500 parts per reel
STOD2540 2/19 contents 1 schematic 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 demoboard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 7 typical performance characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 8 package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 9 revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
STOD2540 schematic diagram 3/19 1 schematic diagram figure 1. block diagram
pin configuration STOD2540 4/19 2 pin configuration figure 2. pin connections (top view) table 1. pin description pln n symbol note 1v i supply voltage 2 rset peak inductor current adjust 3 agnd analog ground 4 fb feedback for the led current regulation 5v o output voltage for led supply 6 vcap load disconnect switch input 7 enable ic enable signal 8 vsw boost switch drain 9 pgnd power ground
STOD2540 maximum ratings 5/19 3 maximum ratings table 2. 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 3. thermal data symbol parameter value unit r thja thermal resistance junction-ambient 52 c/w
electrical characteristics STOD2540 6/19 4 electrical characteristics table 4. electrical characteristics (t j = 40c to 85c, v i = 3.6v, v en = 3v, c i = c o = 4.7f, l = 4.7h, r 1 = 180k ? , r 2 = 10k ? , v o = 24v, typ. values @ 25c, unless otherwise specified). symbol parameter test min. typ. max. unit v i input voltage range 3.0 5.5 v v o regulated output voltage v i = 3v to 5.5v v i + 0.5 25 35 v v ovp over voltage protection on output 35 v i o continuous output current v o = 25v 140ma i sd stand-by current v en = low, v i = 3.6v 3 a v en = low, v i = 3v to 4.2v 10 i q quiescent current consumption v i = 3v to 4.2v @ 25c 0.4 0.8 ma v i = 5.5v @ 25c 0.8 1.2 r dson-sw boost switch r dson note: 1 v i = 4.2v, i sw = 100ma 0.4 ? bvds breakdown voltage 40 v r dson- lds r dson note: 1 v o = 25v, i o = 30ma 2 ? bvds breakdown voltage 40 v i lim-adj peak inductor limit range note: 1 r set = 10k ? to 100k ? 0.2 1.1 a i lim-max maximum peak inductor current note: 1 v i = 3v to 5.5v, r set = v i 0.75 1.2 a fb feedback voltage 5% @ 25c 1.18 1.24 1.30 v t on_max maximum on time v i = 4.2v 5.5 s t off_min minimum off time v i = 4.2v 300 ns eff efficiency, v i = 3.6v note: 1 i o = 1 ma to 5ma 65 % i o = 5 ma to 40ma 70 efficiency, v i =4.2v note: 1 i o = 1 ma to 5ma 65 i o = 5 ma to 40ma 70 ripple output ripple and noise v i = 3.6v, i o = 5 ma, v o = 24v 1.3 % v i = 3.6v, i o = 30 ma, v o = 24v 1.3 v i = 4.2v, i o = 5 ma, v o = 24v 1.3 v i = 4.2v, i o = 30 ma, v o = 24v 1.3 ov hyst overvoltage hysteresis 2 v
STOD2540 electrical characteristics 7/19 note: 1 guaranteed by design. 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 = 3v to 5.5v, i o = 5 ma 5 35 mv load_v fb line regulation v fb v i = 3v to 5.5v, i o = 5 ma 5 35 mv table 4. electrical characteristics (t j = 40c to 85c, v i = 3.6v, v en = 3v, c i = c o = 4.7f, l = 4.7h, r 1 = 180k ? , r 2 = 10k ? , v o = 24v, typ. values @ 25c, unless otherwise specified). symbol parameter test min. typ. max. unit
functional description STOD2540 8/19 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 reference 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 (300ns typical) has passed and the feedback voltage is below the reference again. a maximum on time of 4s 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: 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 rset and gnd, the peak current limit can be adjusted from 200ma to 1.1a (r set from 10k ? to 100k ? ). when the pin r set is directly connected to v i , the default value is 1a. 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 (1.2v STOD2540 functional description 9/19 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 1ma. 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 undervoltage lockout circuit operates with typical threshold 2.8v. when supply voltage is below 3.0v, possible noise in the supply line could disturb the uvlo circuit causing loss of output regulation. this behavior is eliminated choosing c i = 10f or higher.
typical application STOD2540 10/19 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 5. external components (see fig. 3 and note) symbol parameter test min. typ. max. unit d boost schottky diode vrrm 30 v v f at i f = 300ma, t j = 25c 0.5 v i r at v r = 10v, t j = 25c 30 a r 1 feedback resistor 180 k ? r 2 feedback resistor 10 r set peak current limit adjust i pk = 200ma to 1.1a 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 ? l boost inductor (height < 2mm) inductance 4.7 h i sat , r set pin to v i 1a
STOD2540 typical application 11/19 6.1 demoboard figure 4. suggested demoboard schematic (top layer view)
typical performance characteristics STOD2540 12/19 7 typical performance characteristics (t j = 40c to 85c, v i = 3.6v, v en = 3v, c i = c o = 4.7f, l = 4.7h, r 1 = 180k ? , r 2 = 10k ? , v o = 24v, typ. values @ 25c, 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 13/19 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 14/19 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 15/19 8 package mechanical data in order to meet environmental requirements, st offers these devices in ecopack ? packages. these packages have a lead-free second level interconnect. the category of second level interconnect is marked on the package and on the inner box label, in compliance with jedec standard jesd97. the maximum ratings related to soldering conditions are also marked on the inner box label. ecopack is an st trademark. ecopack specifications are available at: www.st.com.
package mechanical data STOD2540 16/19 dim. mm. inch min. typ max. min. typ. max. a 0.80 0.90 1.00 0.032 0.035 0.039 a1 0.03 0.05 0.001 0.002 a2 0.65 0.70 0.75 0.026 0.028 0.030 a3 0.15 0.20 0.25 0.006 0.008 0.010 b 0.29 0.31 0.39 0.011 0.012 0.015 b1 0.17 0.30 0.007 0.012 d 3.00 0.118 d2 1.92 2.02 2.12 0.076 0.080 0.084 e 3.00 0.118 e2 1.11 1.21 1.31 0.044 0.048 0.052 e 0.65 0.026 k 0.20 0.008 l 0.20 0.29 0.45 0.008 0.011 0.018 l1 0.16 0.24 0.40 0.006 0.009 0.016 l2 0.13 0.005 r 0.15 0.006 r1 0.15 0.006 qfn8 (3x3) mechanical data 7517789
STOD2540 package mechanical data 17/19 dim. mm. inch min. typ max. min. typ. max. a 330 12.992 c 12.8 13.2 0.504 0.519 d20.2 0.795 n60 2.362 t 18.4 0.724 ao 3.3 0.130 bo 3.3 0.130 ko 1.1 0.043 po 4 0.157 p 8 0.315 tape & reel qfnxx/dfnxx (3x3) mechanical data
revision history STOD2540 18/19 9 revision history table 6. revision history date revision changes 22-mar-2006 1 initial release. 03-apr-2006 2 add fig. 2 demoboard 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 3.6v ==> 4.2v.
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