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january 2012 doc id 15770 rev 2 1/22 22 STP4CMP low voltage 4-channel constant current led driver with charge pump features operating voltage range: v cc (opr) = 2.7 v to 5.5 v full rgb function support 4-channel led driver with individual on/off control directly from input pins individual programmable output current for the 4 channels through 4 external resistors with a max. capability of 30 ma absolute output current accuracy of max. 7% and channel-to-channel mismatch of max. 4% selectable charge pump enable/disable thermal protection small qfn20 (1.8 x 3.2 mm) package applications mobile phone display backlighting rgb led indicator drivers description the STP4CMP is a charge pump based 4- channel led driver designed for rgb illumination or lcd display backlighting. the STP4CMP works off a battery with an input voltage between 2.7 v - 5.5 v. the device generates regulated current sinks with high absolute and channel-to- channel accuracy to drive up to 4 leds. it can support leds with forward voltage as high as 3.8 v. the current sink for each channel can be set with 4 individual external resistors. each channel is controlled independently. the pwm control can be applied directly to the 4 en (enable) pins to provide brightness control. when enabled, the charge pump, which uses a small ceramic bucket capacitor between c1p and c1n, operates to regulate the v out with a clamping voltage at typ. 5 v. the tiny qfn20 (1.8 x 3.2 mm) package allows the device to be also used for applications with space limitation. qfn20 (1.8 x 3.2 mm) table 1. device summary order code package packaging STP4CMPqtr qfn20 tape and reel www.st.com
contents STP4CMP 2/22 doc id 15770 rev 2 contents 1 schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3 maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 4 electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 5 detailed description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 5.1 enable pin (en) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 5.2 led turn-on pin (onx) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 5.3 programmable output current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 5.4 charge pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 5.5 thermal protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 6 typical performance characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 7 pcb layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 7.1 recommended . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 7.2 demonstration board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 7.3 demonstration board schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 8 package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 9 revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
STP4CMP schematic doc id 15770 rev 2 3/22 1 schematic figure 1. application schematic figure 1 shows the typical application diagram with the external components. to ensure an optimal charge pump performance, it is highly recommended that the bucket capacitor, c1, and the output capacitor, c out , to be placed as close as possible to the pins. note: all the above components refer to a typical application. operation of the device is not limited to the choice of these external components. table 2. typical external components component manufacturer part number value size c1- c out murata grm155r61a105ke15d 1 f / 10 v 0402 tdk c1005x5r1a105mt c2 murata grm188r60j106me84 10 f / 6.3 v 0603 tdk c1608x5r0j106mt c3 murata grm155r60j104ka01d 100 nf 0402 tdk c1005x5r1c104kt r set1-4 (1) 1. r set1-4 : 649 - 7.87 k according to the desired output current from each channel. tyco cpf0402b976re1 976 0402 led1-4 (2) 2. led1-4: typ. forward voltage of 3.8 v. am0079 8 v1 led2 led3 led4 c 1n on1 on2 on3 c 1p i set1 gnd en led1 v out v cc r set1 on4 i set2 r set2 i set3 r set3 i set4 r set4 cp_sel gnd c1 c2 c out led1 led2 led3 led4 c3
schematic STP4CMP 4/22 doc id 15770 rev 2 figure 2. block schematic & 1 &kdujhsxps &xuuhqwpluuruv 21 21 21 & 3 , 6(7 *1' (1 /(' /(' /(' /(' 9 287 9 && 5 6(7 21 , 6(7 5 6(7 , 6(7 5 6(7 , 6(7 5 6(7 &3b6ho 7khupdosurwhfwlrq %dqgjdsuhihuhqfh !-6
STP4CMP pin configuration doc id 15770 rev 2 5/22 2 pin configuration figure 3. pin connection (top through view) table 3. pin description pin number symbol name and function 1 on1 led1 enable 2 on2 led2 enable 3 on3 led3 enable 4 on4 led4 enable 5 en chip enable 6i set1 led1 max. current setting resistor 7i set2 led2 max. current setting resistor 8i set3 led3 max. current setting resistor 9i set4 led4 max. current setting resistor 10 gnd ground 11 cp_sel charge pump mode selection, ?1? => enable; ?0? => disable 12 led4 4 th led current sink 13 led3 3 rd led current sink 14 led2 2 nd led current sink 15 led1 1 st led current sink 16 v cc supply voltage 17 v out charge pump output 18 c 1p positive terminal of charge pump bucket capacitor 340#-0 !-6
pin configuration STP4CMP 6/22 doc id 15770 rev 2 pin number symbol name and function 19 c 1n negative terminal of charge pump bucket capacitor 20 gnd ground table 3. pin description (continued)
STP4CMP maximum ratings doc id 15770 rev 2 7/22 3 maximum ratings note: absolute maximum ratings are those values beyond which damage to the device may occur. functional operation under these conditions is not implied. table 4. absolute maximum ratings symbol parameter value unit on 1-4 ; v cc ; en; cp_sel; c 1p ; c 1n ; supply voltage - 0.3 to +6 v vout output voltage - 0.3 to +6 v led 1-4 ; iset 1-4 current setting - 0.3 v to 2 v esd machine model 200 v human body model (mil std_883) 1500 charged device model 500 t amb operating ambient temperature - 30 to 85 c t j maximum operating junction temperature + 150 c t stg storage temperature - 65 to 150 c table 5. recommended operating conditions symbol parameter value unit min. typ. max. v cc supply voltage 2.7 - 5.5 v t op operating temperature -40 - 85 c i led current through each led 2.5 - 30 ma t pwm_on on time of pwm signal at each on pin 33 - s t pwm_off off time of pwm signal at each on pin 33 - s v fw led forward voltage - 3.8 v table 6. thermal data symbol parameter value unit r thja (1) 1. this parameter corresponds to the pcb boar d, 4-layers with 1inch2 of cooling area. junction to ambient thermal resistance 70 c/w
electrical characteristics STP4CMP 8/22 doc id 15770 rev 2 4 electrical characteristics v cc =3.3v, v en =v on1 =v on2 =v on3 =v on4 =v cc , v cp_sel = v cc , r set1 = r set2 = r set3 = r set4 = 649 , c1 =1 f, typical values are at t a =25c, unless otherwise specified. table 7. electrical characteristics symbol parameter test condition min. typ. max. unit v cc supply voltage 2.7 5.5 v v cp_clamp charge pump clamp voltage 2.7 v v cc < 3.1 v; v cp_sel = v cc; i out 40 ma 5 v v cc > 3.1 v; v cp_sel = v cc; i out 120 ma 5 t cp_start charge pump startup time from cp_sel low to high transition to cp reaches steady-state at 5 v 10 ms i led1,2,3,4 led sink current for each channel r setx = 649 at v ledx =0.9 v; v cc > 3.1 v 27.9 30 32.1 ma r setx = 7.87 k at v ledx = 0.9 v; v cc 3.1 v 2.33 2.5 2.68 ma i led output current error between each channel r set1 =r set2 =r set3 =r set t a = 25 c 1 4 % v ih high level input voltage 2.0 v v il low level input voltage 0.8 v i cc supply operating current v on1 =v on2 =v on3 =v on4 =g nd; no load; v cc =5.5 v (charge pump disabled); v cp_sel =gnd, r set1 =r set2 =r set3 =r set4 = 7.87 k 3.6 ma v on1 =v on2 =v on3 =v on4 =g nd; no load; v cc =5.5 v (charge pump disabled); v cp_sel =gnd, r set1 =r set2 =r set3 =r set4 = 649 1.7 v on1 =v on2 =v on3 =v on4 =g nd; no load; v cc =3.3 v (charge pump disabled); v cp_sel =v cc , r set1 =r set2 = 7.87 k 4.5 v on1 =v on2 =v on3 =v on4 =g nd; no load; v cc =3.3 v (charge pump disabled); v cp_sel =v cc , r set1 =r set2 =r set3 =r set4 = 649 17.2
STP4CMP electrical characteristics doc id 15770 rev 2 9/22 symbol parameter test condition min. typ. max. unit i shutdown supply current during power-down v en =v on1 =v on2 =v on3 =v on 4 =v cp_sel = 0 v 5a t sd thermal shutdown 150 c t hs thermal shutdown hysteresis 15 c table 7. electrical characteristics (continued)
detailed description STP4CMP 10/22 doc id 15770 rev 2 5 detailed description the STP4CMP is a charge-pump-based 4-channel led driver designed for rgb illumination or lcd display backlighting, using constant current topology. each of the 4 channels can be controlled independently. when onx is pulled high, a constant current is sunk into the ledx pin when a led is connected. this constant current is defined or programmed by the value of the resistor at i setx pin. 5.1 enable pin (en) the active high enable input pin is used to shut down the whole device. when this pin is pulled low, the device enters into shutdown mode with only 5 a max. current consumption. an internal pulled down of 300 k is present at this pin. 5.2 led turn-on pin (onx) when the en pin is pulled high, the STP4CMP provides the flexibility to control the turning- on/off on the 4 channels independently through the 4 active high on pins. to control the brightness of each led channel, it is possible to drive the selected on pin with a pwm signal with a frequency up to a minimum t on /t off of 33 s. an internal pull-down of 300 k is present at these pins. 5.3 programmable output current the led currents at the 4 channels are programmed individually through a resistor connected from i set1 , i set2 , i set3 , i set4 to ground. the relationship between the resistor (r set ) and the led current (i led ) is governed by this equation: equation 1 r set = 16 * (1.22 / i led ) 5.4 charge pump the STP4CMP charge pump can be disabled or enabled according to the cp_sel pin. when enabled (cp_sel is high), the charge pump provides a clamping voltage of typ 5.0 v to ensure enough headroom to drive the leds. an internal pull-down of 300 k is present at this pin. the charge pump can be disabled by pulling low the cp_sel pin, based on the v cc and forward voltage of the leds used. this allows the connection of v cc directly to v out to drive the external leds. at v cc 3.1 v, the charge pump is able to maintain regulation at 5 v when the total current drawn from it (at v out pin) is 120 ma. at 2.7 v cc < 3.1 v, in order for the charge pump to maintain regulation at 5 v, the total current drawn from it (at v out pin) must be lowered to 40 ma.
STP4CMP detailed description doc id 15770 rev 2 11/22 5.5 thermal protection the thermal protection circuit ensures device shutdown when it is overheated (for example, due to an output short-circuit) to typ. 150 c. the device resumes normal operation when the temperature drops by 15 c from the thermal shutdown threshold.
typical performance characteristics STP4CMP 12/22 doc id 15770 rev 2 6 typical performance characteristics figure 4. eff. vs.v in , i out = 10 ma figure 5. eff. vs.v in , i out = 60 ma figure 6. v out vs.v in am10404v1 15 17 19 21 2 3 25 27 29 3 0 3 5 40 45 50 55 60 65 70 75 8 0 8 5 90 95 100 2.7 3 .0 3 .2 3 .5 3 .7 4.0 4.2 4.5 4.7 5.0 5.2 5.5 i in [ma] eff [%] v in [v] eff iin am10405v1 200 210 220 2 3 0 240 250 260 3 0 3 5 40 45 50 55 60 65 70 75 8 0 8 5 90 95 100 2.7 3 .0 3 .2 3 .5 3 .7 4.0 4.2 4.5 4.7 5.0 5.2 5.5 i in [ma] eff [%] v in [v] eff iin am10406v1 4.50 4.55 4.60 4.65 4.70 4.75 4. 8 0 4. 8 5 4.90 4.95 5.00 2.6 2.9 3 .1 3 .4 3 .6 3 .9 4.1 4.4 4.6 4.9 5.1 5.4 v out [v] v in [v]
STP4CMP typical performance characteristics doc id 15770 rev 2 13/22 figure 7. pwm modulation ch1-2 figure 8. output ripple
pcb layout STP4CMP 14/22 doc id 15770 rev 2 7 pcb layout 7.1 recommended the STP4CMP is a charge pump power device so it requires a proper pcb layout in order to obtain the necessary stability and optimize line/load regulation and output voltage ripple. input, output, and boost capacitors must be as close as possible to their relative pins. figure 9. top layer figure 10. bottom layer
STP4CMP pcb layout doc id 15770 rev 2 15/22 figure 11. top overlay 7.2 demonstration board figure 12. demonstration board
pcb layout STP4CMP 16/22 doc id 15770 rev 2 7.3 demonstration board schematic figure 13. demonstration board schematic vc c vc c c1n c1p vou t led1 led2 led 3 led4 vc c 10k r 3 10k r4 10k r5 10k r6 10k r1 1k r7 1k r 8 1k r9 1k r10 10k r2 vou t 1 2 3 jp5 vc c 1 2 3 jp1 vc c 1 2 3 jp 3 vc c 1 2 3 jp4 vc c 1 2 3 jp6 vc c 1 2 3 jp2 1 f c4 1 f c1 10 f c2 vc c 100n c 3 1 2 p2 1 2 p 3 1 2 p4 1 2 p5 1 2 p9 1 2 p 8 1 2 p1 0 1 2 p7 1 2 p6 vc c cp_ s el i s et1 i s et2 i s et 3 i s et4 on1 on2 on 3 on4 en 1 2 led4 led 3 led2 led1 c1n 19 c1p 1 8 vou t 17 vc c 16 led1 15 led2 14 led 3 1 3 led4 12 i s et4 9 i s et 3 8 i s et2 7 i s et1 6 en 5 on4 4 on 3 3 on2 2 on1 1 gnd 20 gnd 10 cp_ s el 11 u1 s tp4cmp 1 2 p1 p u lldown re s i s tor s r1 - r 6 to g ua r a nt e e c orre c t f u nction when no j u mp e r i s pl a ced. for efficiency me asu rement s , p u ll down s s ho u ld b e removed to me asu re correct dut inp u t c u rrent, otherwi s e p u lldown re s i s tor s c u rrent wo u ld a ffect the re su lt. p u lldown re s i s tor s r7 - r 1 0 a re s et re s i s tor s for e a ch ch a nnel. needed to b e ch a nged for different o u tp u t c u rrent s et u p. p6 - p10 he a de r a re us ed to lo a d o u tp u t s when no led i s pop u l a ted. 1 2 1 2 1 2 am10407v1
STP4CMP package mechanical data doc id 15770 rev 2 17/22 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. figure 14. package outline for qfn20 (1.8 x 3.2 x 0.5 mm) - pitch 0.4 mm
package mechanical data STP4CMP 18/22 doc id 15770 rev 2 figure 15. footprint recommendations for qfn20 (1.8 x 3.2 x 0.5 mm) - pitch 0.4 mm 1. drawing not to scale. 2. dimensions are in millimeters. table 8. mechanical data for qfn20 (1.8 x 3.2 x 0.5 mm) - pitch 0.4 mm symbol millimeters min. typ. max. a 0.45 0.50 0.55 a1 0 0.02 0.05 a3 0.127 b 0.15 0.20 0.25 d 3.15 3.20 3.25 e 1.75 1.80 1.85 e 0.40 l 0.35 0.40 0.45
STP4CMP package mechanical data doc id 15770 rev 2 19/22 figure 16. carrier tape for qfn20 (1.8 x 3.2 x 0.5 mm) - pitch 0.4 mm $0y
package mechanical data STP4CMP 20/22 doc id 15770 rev 2 figure 17. reel information for qfn20 (1.8 x 3.2 x 0.5 mm) - pitch 0.4 mm 1. drawing not to scale. 2. dimensions are in millimeters
STP4CMP revision history doc id 15770 rev 2 21/22 9 revision history table 9. document revision history date revision changes 09-jun-2009 1 initial release. 24-jan-2012 2 document status promoted from preliminary data to datasheet. added section 7 on page 14 .
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