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preliminary EMD2794/emd2795 elite micropower inc. elite micropower inc. reserves the right to make changes to improve reliability or manufa cturability without notice, and customers are advised to obtain the latest version of relevant information prior to placing orders. dsd2794/2795_v2.1 january 21 th 2008 page 1 of 14 www.elitemicropower.com regulated switched capacitor led current source with analog and pwm brightness control general description the EMD2794/emd2795 is a 1.5x/1.0x charge pump that provides four regulated current sources. it accepts an input voltage range from 2.7v to 5.5v and maintains a constant current determined by an external resistor. the EMD2794/emd2795 delivers up to 80ma of load current to accommodate four white leds. the switching frequency is fixed at 1.2mhz to make noise filtering easier. brightness control can be done by both linear and pwm techniques. linear control is achieved by applying 0v to 3.0v to the brgt pin to linearly vary the led current. pwm technique is to apply a clock to the en pin to having brightness varying with clock duty. shutdown is done by applying low (high for 2795) to the pin en. the vin current drops to less than 1.0ua in shutdown mode. the EMD2794/emd2795 is available in a tqfn-16 & fbp-16 3x3 package. features ? regulated current sources with 0.5% matching between any two outputs ? high efficiency 3/2 boost function ? drives one to four white leds. ? 2.7v to 5.5v input range ? up to 80ma output current ? analog brightness control ? active-low or high shutdown input (?94/95) ? very small solution size and no inductor ? shutdown current < 1 a ? 1.2mhz switching frequency ? constant frequency generates predictable noise spectrum ? qfn16 3x3 package applications ? white led display backlights ? white led keypad backlights ? 1-cell li-ion battery-operated equipment including pdas, hand-held pcs, cellular phones. micro bridge technology co.,ltd.
preliminary EMD2794/emd2795 elite micropower inc. elite micropower inc. reserves the right to make changes to improve reliability or manufacturability without notice, and customers are advised to obtain the latest versio n of relevant information prior to placing orders. dsd2794/2795_v2.1 january 21 th 2008 page 2 of 14 www.elitemicropower.com connection diagram tqfn-16 1 2 3 4 c2n gnd vin c1n 5 6 7 8 c1p pout c2p en 12 11 10 9 sout d4 iset brgt 16 15 14 13 nc d1 d2 d3 order information EMD2794-00hb16nrr / emd2795-00hb16nrr 00 voltage option hb16 tqfn-16 package n green ; (rohs & halogen free) r commercial grade temperature rating: -40 to 85c r package in tape & reel fbp-16 1 2 3 4 c2n gnd vin c1n 5 6 7 8 c1p pout c2p en 12 11 10 9 sout d4 iset brgt 16 15 14 13 nc d1 d2 d3 EMD2794-00ba16grr / emd2795-00ba16grr 00 voltage option ba16 fbp-16 package g rohs( pb free) r commercial grade temperature rating: -40 to 85c r package in tape & reel micro bridge technology co.,ltd.
preliminary EMD2794/emd2795 elite micropower inc. elite micropower inc. reserves the right to make changes to improve reliability or manufa cturability without notice, and customers are advised to obtain the latest version of relevant information prior to placing orders. dsd2794/2795_v2.1 january 21 th 2008 page 3 of 14 www.elitemicropower.com marking & packing information product id package type product id package marking transport media tqfn-16 EMD2794-00hb16nrr EMD2794 fbp-16 EMD2794-00ba16grr 5k units tape & reel tqfn-16 by request emd2795 fbp-16 by request 5k units tape & reel yy: year code ww: weekly code micro bridge technology co.,ltd.
preliminary EMD2794/emd2795 elite micropower inc. elite micropower inc. reserves the right to make changes to improve reliability or manufa cturability without notice, and customers are advised to obtain the latest version of relevant information prior to placing orders. dsd2794/2795_v2.1 january 21 th 2008 page 4 of 14 www.elitemicropower.com typical applications vin(3) c1p(5) c1n(4) c2p(7) gnd(2) brgt(9) en(8) c2n(1) (10)iset (15)d1 (6)pout (12)sout cin 1uf 2794: h enable 2795: l enable c2 1uf c1 1uf 0~3v cout 1uf rset EMD2794/95 led1 (14)d2 led2 (13)d3 (11)d4 led3 led4 micro bridge technology co.,ltd.
preliminary EMD2794/emd2795 elite micropower inc. elite micropower inc. reserves the right to make changes to improve reliability or manufa cturability without notice, and customers are advised to obtain the latest version of relevant information prior to placing orders. dsd2794/2795_v2.1 january 21 th 2008 page 5 of 14 www.elitemicropower.com absolute maximum ratings (note 1) v in -0.5 to 6.2v en -0.5 to 6.2v brgt -0.5 to min[(vin+0.3), 6.2v] continuous power dissipation (note 2) internally limited t jmax (note 2) 135 o c storage temeprature -60 o c to +150 o c lead temp. (soldering, 5 sec.) 260 o c esd rating human body model 2kv machine model 200v recommended operating conditions v in 2.7 to 5.5v ambient temperature (ta) -30c to +85c junction temperature (tj) -30c to +100c electrical characteristics limits in standard typeface are for tj=25 o c and limits in boldface type apply over the full operating junction temperature range (-30 o cQ tj Q +100 o c). unless otherwise specified, c 1 =c 2 =c in =c out =1uf, v in =3.6v, brgt pin =0v; r set =12 4 ; EMD2794: v en =v in (emd2795: v en =0v). symbol parameter conditions min typ max units note i dx available current 3.0v Qv in Q5.5v v dx Q3.8v, brgt=50mv 16.7 ma i d-match current matching between any two outputs v dx =3.6v 0.5 % i q quiescent supply current 3.0v Qv in Q4.2v, active, no load, r set =open 3.2 ma i sd shutdown supply current 3.0v Qv in Q5.5v, shutdown 1 ua i pull-en en pull-high current (emd2795) 3.2 ua v cp 1.5x to 1.0x threshold 4.75 v v cph 1.0x to 1.5x hysteresis 300 mv v ih en input logic high (EMD2794) 1.0 en input logic high (emd2795) 0.8v in v il en input logic low (EMD2794) 0.4 v en input logic low (emd2795) 0.2v in r brgt brgt input resistance 240 k f sw switching frequency 3.0v Qv in Q5.5v 1.2 mhz note 1: absolute maximum ratings indicate limits beyond which damage to the device may occur. electrical specifications do not apply when operating the device beyond its rated operating conditions. note 2: internal thermal shutdown circuitry protects the device from permanent damage. thermal shutdown engages at tj=150c (typ.) and disengages at tj=140c (typ.). micro bridge technology co.,ltd.
preliminary EMD2794/emd2795 elite micropower inc. elite micropower inc. reserves the right to make changes to improve reliability or manufa cturability without notice, and customers are advised to obtain the latest version of relevant information prior to placing orders. dsd2794/2795_v2.1 january 21 th 2008 page 6 of 14 www.elitemicropower.com pin descriptions 1 2 3 4 c2n gnd vin c1n 5 6 7 8 c1p pout c2p en 12 11 10 9 sout d4 iset brgt 16 15 14 13 nc d1 d2 d3 1 2 3 4 c2n gnd vin c1n 5 6 7 8 c1p pout c2p en 12 11 10 9 sout d4 iset brgt 16 15 14 13 nc d1 d2 d3 tqfn- 16 pin 3mm x 3mm, top view fbp-16 pin 3mm x 3mm, top view pin name pin order descriptions c2n 1 negative terminal of c2 gnd 2 power supply ground input vin 3 power supply voltage input c1n 4 negative terminal of c1 c1p 5 positive terminal of c1 pout 6 charge pump output. connect 1uf ceramic capacitor at this pin. c2p 7 positive terminal of c2 en 8 the EMD2794 has an active-low shutdown pin (low = shutdown, high = operating). the emd2795 has an active-high shutdown pin (high = shutdown, low = operating) that has a pull-up to v in . brgt 9 variable voltage input controls output current iset 10 current sense input. connect 1% resistor to ground to set constant current through led. d4 11 current source outputs. connect directly to led. sout 12 charge pump input. connect directly to pin pout. (please refer to typical application.) d3 13 current source outputs. connect directly to led. d2 14 current source outputs. connect directly to led. d1 15 current source outputs. connect directly to led. nc 16 ep ep exposed paddle (bottom); connect to gnd directly beneath package. micro bridge technology co.,ltd.
preliminary EMD2794/emd2795 elite micropower inc. elite micropower inc. reserves the right to make changes to improve reliability or manufa cturability without notice, and customers are advised to obtain the latest version of relevant information prior to placing orders. dsd2794/2795_v2.1 january 21 th 2008 page 7 of 14 www.elitemicropower.com typical performance characteristics unless otherwise specified, c1=c2=cin=cout, vin=3.6v, brgt=0v, rset=124 id io d e vs vin 14.500 14.750 15.000 15.250 15.500 15.750 16.000 16.250 2.70 3.20 3.70 4.20 4.70 5.20 5.70 vin(v) idiode(ma) idiode vs brgt 0.0 ma 2.0 ma 4.0 ma 6.0 ma 8.0 ma 10.0 ma 12.0 ma 14.0 ma 16.0 ma 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 brgt(v) idiode(ma) rset=999 rset=2499 id io d e vs vd io d e 15.00 15.25 15.50 15.75 16.00 3.0 3.2 3.4 3.6 3.8 4.0 veio d e(v) idiode(ma) vset vs vbrgt, rset=1k 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 0.00.51.01.52.02.53.0 vbrgt(v) vset(v) duty cycle vs. led curent, idiode 1-4 = 15ma 0 2 4 6 8 10 12 14 16 0 % 20 % 40 % 60 % 80 % 100 % duty cycle (%) idiode(ma) supply current vs vin, id1-4=15ma 0.0 ma 20.0 ma 40.0 ma 60.0 ma 80.0 ma 100.0 ma 120.0 ma 2.7 3.2 3.7 4.2 4.7 5.2 5.7 vin(v) isupply(ma) micro bridge technology co.,ltd.
preliminary EMD2794/emd2795 elite micropower inc. elite micropower inc. reserves the right to make changes to improve reliability or manufa cturability without notice, and customers are advised to obtain the latest version of relevant information prior to placing orders. dsd2794/2795_v2.1 january 21 th 2008 page 8 of 14 www.elitemicropower.com typical performance characteristics unless otherwise specified, c1=c2=cin=cout, vin=3.6v, brgt=0v, rset=124 supply current vs vin, id1-4&iset open 0 2 4 6 8 10 12 2.7 3.2 3.7 4.2 4.7 5.2 5.7 vin(v) isupply(ma) switching frequency 1.06 1.16 1.26 1.36 1.46 1.56 2.73.23.74.24.7 vin(v) frequency (mhz) micro bridge technology co.,ltd.
preliminary EMD2794/emd2795 elite micropower inc. elite micropower inc. reserves the right to make changes to improve reliability or manufa cturability without notice, and customers are advised to obtain the latest version of relevant information prior to placing orders. dsd2794/2795_v2.1 january 21 th 2008 page 9 of 14 www.elitemicropower.com function block diagram application information circuit description the EMD2794/5 is a 1.5x/1.0x charge pump with four matched constant current outputs, each capable of driving up to 20ma. this device operates over the extended li-ion battery range from 2.7v to 5.5v. at input voltages below 4.75v (typ.), the charge-pump provides the needed voltage to drive high forward voltage drop leds by stepping up the pout voltage 1.5 times the input voltage. the charge pump provides a voltage on pout equal to the input voltage when the input voltage is at or above 4.75v (typ.). the EMD2794/5 can drive up to 80ma through any combination of leds connected to the constant current outputs d1-d4. the EMD2794/5 uses a resistor co nnected to the iset pin to set a reference current. this reference current is then multiplied 10 times to each constant current output. the led brightness can then be controlled by analog and/or digital methods. applying an analog voltage in the range of 0v to 3.0v to the brightness pin (brgt) adjusts the dimming profile of the leds. the digital technique uses a pwm (pulse width modulation) signal applied to the enable pin (en). soft start soft start is implemented internally by ramping the reference voltage more slowly than the applied voltage. during soft start, the current through the led outputs will ramp up in proportion to the rate that the reference voltage is being ramped up. shutdown mode the enable pin (en) disables the device and reduces the quiescent current to below than 1ua. the emd2795 has an active-low enable pin (high = shutdown, low = operating). an internal pull-up is connected between en and vin of the emd2795. this allows the use of open-drain logic control of the emd2795 shutdown. the emd2795 en 1.5x/1.0x charge pump 3ua, only on emd2795 vref brightness control sout pout d4 d3 d2 d1 c1p c1n c2p c2n vin en brgt iset gnd micro bridge technology co.,ltd.
preliminary EMD2794/emd2795 elite micropower inc. elite micropower inc. reserves the right to make changes to improve reliability or manufa cturability without notice, and customers are advised to obtain the latest version of relevant information prior to placing orders. dsd2794/2795_v2.1 january 21 th 2008 page 10 of 14 www.elitemicropower.com pin can also be driven with a rail-to-rail cmos logic signal. the EMD2794 has an active-high enable pin (low = shutdown, high = operating). the EMD2794 en pin can be driven with a low-voltage cmos logic signal (1.5v logic, 1.8v logic, etc). there is no internal pull-up or pull-down on the en pin of the EMD2794. capacitor selection the EMD2794/5 requires 4 external capacitors for proper operation. surface-mount multi-layer ceramic capacitors are recommended. these capacitors are small, inexpensive and have very low equivalent series resistance (esr, 15m ? typ.). for most applications, ceramic capacitors with x7r or x5r temperature characteristic are preferred for use with the EMD2794/5. these capacitors have tight capacitance tolerance (as good as 10%), hold their value over temperature (x7r: 15% over ? 55c to 125c; x5r: 15% over ? 55c to 85c), and typically have little voltage coefficient. capacitors with y5v or z5u temperature characteristic are generally not recommended for use with the EMD2794/5. led selection the EMD2794/5 is designed to drive leds with a forward voltage of about 3.0v to 4.0v. the typical and maximum diode forward voltage depends highly on the manufacturer and their technology. forward current matching is assured over the led process variations due to the constant current output of the EMD2794/5. i set and brgt pins an external resistor, rset, is connected to the iset pin to set the current to be mirrored in each of the led outputs. the internal current mirror sets each led output current with a 10:1 ratio to the current through rset. the current mirror circuitry matches the current through each led to within 0.5%. in addition to rset, a voltage may be applied to the vbrgt pin to vary the led current. by adjusting current with the brightness pin (brgt), the brightness of the leds can be smoothly varied. applying a voltage on brgt between 0 to 3 volts will linearly vary the led current. an equation for approximating the led current is: i led =(0.188 + 0.385 * v brgt ) / r set * 10 amps i led current selection procedures the following procedures illustrate how to set and adjust output current levels. for constant brightness or analog brightness control, go to ?bri ghtness control using brgt?. otherwise refer to ?brightness control using pwm?. brightness control using pwm 1. set the brgt pin to 0v. 2. determine the maximum desired iled current. use the iled equation to calculate rset by setting brgt to 0v or use table 1 to select a value for rset when brgt equals 0v. 3. brightness control can be implemented by pulsing a signal at the en pin. led brightness is proportional to the duty cycle (d) of the pwm signal. for linear brightness control over the full duty cycle adjustment range, the pwm frequency (f) should be limited to accommodate the turn-on time (ton = 100 s) of the device. d x (1/f) > ton fmax = dmin ton if the pwm frequency is much less than 100hz, flicker may be seen in the leds. for the EMD2794, zero duty cycle will turn off the leds and a 50% duty cycle will result in an average iled being half of the programmed led current. for example, if rset is set to program 15ma, a 50% duty cycle will result in an average iled of 7.5ma. for the emd2795 however, micro bridge technology co.,ltd.
preliminary EMD2794/emd2795 elite micropower inc. elite micropower inc. reserves the right to make changes to improve reliability or manufa cturability without notice, and customers are advised to obtain the latest version of relevant information prior to placing orders. dsd2794/2795_v2.1 january 21 th 2008 page 11 of 14 www.elitemicropower.com 100% duty cycle will turn off the leds and a 50% duty cycle will result in an average iled being half the programmed led current. table 1 r set values led current brgt 5ma 10ma 15ma 20ma 0.0v 37 6 188 125 94 0.5v 761 381 254 190 1.0v 1.15k 573 382 287 1.5v 1.53k 766 510 383 2.0v 1.92k 958 639 479 2.5v 2.30 1.15k 767 575 3.0v 2.69k 1.34k 895 672 brightness control using brgt 1. choose the maximum iled desired and determine the max voltage to be applied to the brgt pin. for constant brightness, set brgt to a fixed voltage between 0v to 3v. 2. use the iled equation above to calculate rset. 3. use table 2 as a reference for the dimming profile of the leds, when brgt ranges from 0v to 3v. table 2 led current led current brgt 2.67k 1.33k 909 665 0.0v 0.7ma 1.4ma 2.1ma 2.8ma 0.5v 1.4ma 2.9ma 4.2ma 5.7ma 1.0v 2.1ma 4.3ma 6.3ma 8.6ma 1.5v 2.9ma 5.8ma 8.4ma 11.5ma 2.0v 3.6ma 7.2ma 10.5ma 14.4ma 2.5v 4.3ma 8.7ma 12.7ma 17.3ma 3.0v 5.0ma 10.1ma 14.8ma 20.2ma charge pump output and input (p out and s out ) the EMD2794/5 charge pump is an unregulated switched capacitor converter with a gain of 1.5. the voltage at the output of the pump (the pout pin) is nominally 1.5 x vin. this rail can be used to deliver additional current to other circuitry. since pout is unregulated, driving leds directly off pout is usually practical only with a fixed input voltage. if the input voltage is not fixed (li-ion battery, for example), using a linear regulator between the pout pin and the leds is recommended. led drivers use power supply from pin sout. to maintain normal operation of led current output, connect pin sout directly to pout on pcb. parallel dx outputs for increased current drive outputs d1 through d4 may be connected together in any combination to drive higher currents through fewer leds. for example, outputs d1 and d2 can be connected together to drive one led while d3 and d4 are connected together to drive a second led. thermal protection when the junction temperature exceeds 150c (typ.), the EMD2794/5 internal thermal protection circuitry disables the part. this feature protects the device from damage due to excessive power dissipation. the device will recover and operate normally when the junction temperature falls below 140c (typ.). it is important to have good thermal conduction with a proper layout to reduce thermal resistance. micro bridge technology co.,ltd.
preliminary EMD2794/emd2795 elite micropower inc. elite micropower inc. reserves the right to make changes to improve reliability or manufa cturability without notice, and customers are advised to obtain the latest version of relevant information prior to placing orders. dsd2794/2795_v2.1 january 21 th 2008 page 12 of 14 www.elitemicropower.com package description tqfn-16 common dimensions millimeter dimensions inch symbol min. nom. max. min. nom. max. a 0.700 0.750 0.800 0.027 0.029 0.031 a3 0.195 0.203 0.211 0.0077 0.0080 0.0083 b 0.180 0.230 0.300 0.007 0.009 0.012 d 2.950 3.000 3.050 0.116 0.118 0.120 e 2.950 3.000 3.050 0.116 0.118 0.120 e 0.50 bsc 0.020 bsc l 0.350 0.400 0.450 0.014 0.016 0.018 d2 1.500 1.625 1.750 0.059 0.064 0.069 e2 1.500 1.625 1.750 0.059 0.064 0.069 micro bridge technology co.,ltd.
preliminary EMD2794/emd2795 elite micropower inc. elite micropower inc. reserves the right to make changes to improve reliability or manufa cturability without notice, and customers are advised to obtain the latest version of relevant information prior to placing orders. dsd2794/2795_v2.1 january 21 th 2008 page 13 of 14 www.elitemicropower.com fbp-16 dimensions millimeter symbol min. nom. max. a 0.800 0.850 0.900 a2 0.153 0.203 0.253 a3 0.000 0.025 0.050 b 0.180 0.230 0.300 d 2.900 3.000 3.100 e 2.900 3.000 3.100 e 0.500 bsc l 0.300 0.400 0.500 d2 1.600 1.700 1.800 e2 1.600 1.700 1.800 micro bridge technology co.,ltd.
preliminary EMD2794/emd2795 elite micropower inc. elite micropower inc. reserves the right to make changes to improve reliability or manufa cturability without notice, and customers are advised to obtain the latest version of relevant information prior to placing orders. dsd2794/2795_v2.1 january 21 th 2008 page 14 of 14 www.elitemicropower.com ? copyright 2005 all rights reserved. no part of this document may be reproduced or duplicated in any form or by any means without the prior permission of emp. the contents contained in this document are believed to be accurate at the time of publication. emp assumes no responsibility for any error in this document, and reserves the ri ght to change the products or specification in this document without notice. the information contained herein is presented only as a guide or examples for the application of our products. no responsibility is assumed by emp for any infringement of patent s, copyrights, or other intellectual property rights of third parties which may result from its use. no license, either express, implied or otherwise, is granted under any patents, copyrights or other intellectual property rights of emp or others. any semiconductor devices may have inherently a certain rate of failure. to minimize risks associated with customer's application, adequate design and operating safeguards agai nst injury, damage, or loss from such failure, should be provided by the customer when making application designs. emp's products are not authorized for use in critical applicatio ns such as, but not limited to, life support devices or system, where failure or abnormal operation may directly affect huma n lives or cause physical injury or property damage. if products described here are to be used for such kinds of ap plication, purchaser must do its own quality assurance testing appropriate to such applications. micro bridge technology co.,ltd.

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