SC604A SEMTECH | Alldatasheet

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Features

June 27, 2005

Description

Applications

Typical Application Circuit The SC604A is a very high efficiency charge pump white LED driver driver from the mAhXLife TM family of products, optimized for Li-Ion battery applications. The four (4) LED outputs are current matched for consis- tent LED brightness. Extremely low battery current is achieved by automatically reconfiguring the charge pump to match circuit conditions. Using four LEDs, each at 20mA for a total I OUT= 80mA, the SC604A can use less than 83mA from the supply for most of the battery life. Patented low noise mode switching circuitry and constant output current allow the use of extremely small input and output capacitors. ‹ Very high efficiency over 90% of battery life ‹ Peak efficiency over 92% ‹ Current regulation for up to 4 LEDs ‹ Digital 3 bit output control logic ‹ Current matching tolerance of ±3% typical ‹ Wide current range per LED [0.5mA - 30mA] ‹ High available total LED current = 4 z ILED = 120mA ‹ Low Shutdown Current: 1µA typical ‹ Soft start / In-rush current limiting ‹ Short circuit protection ‹ MLP-16 [4x4] Package ‹ Fixed frequency 250kHz ‹ 1x, 1.5x and 2x charge pump modes of operation ‹ Cellular phones ‹ LED backlighting ‹ PDA power supplies ‹ Portable devices ‹ Electronic books ‹ Wireless web appliances ‹ LCD Modules Patent Pending VIN EN CTRL0 CTRL1 BATTERY 1µF CTRL2 GND ILED1 ILED2 ILED3 ILED4 VOUT C1+ C1- C2+ C2- SC604A 1µF 1µF 1µF ISET

 2005 Semtech Corp. www.semtech.com SC604A POWER MANAGEMENT Absolute Maximum Ratings

Electrical Characteristics

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 2005 Semtech Corp. www.semtech.com SC604A POWER MANAGEMENT Electrical Characteristics (Cont.) retemaraPl obmySs noitidnoCn iMp yTx aMs tinU timiLtnerruCtupnIT IMILID NGotTUOVmorfdeilppatiucrictrohS0 220 58 Am dlohserhThgiHtupnIV HI dlohserhtcigolhgihtupnI3 .1 V dlohserhTwoLtupnIV LI dlohserhtcigolwoltupnI4 .0 V tnerruChgiHtupnII HI V HI V= NI 01 µA tnerrucwoLtupnII LI V LI DNG=0 1 µA Notes: (1) Guaranteed by design

 2005 Semtech Corp. www.semtech.com SC604A POWER MANAGEMENT Definitions ILED Accuracy The LED current is determined by the R SET resistor (I LED vs. R SET data is found on pages 9 and 10). This term does not include the tolerance of the resistor R SET. If maximum accuracy is required, a precision resistor is needed. To calculate the error I LED-ERR[%], use the formula ILED-ERR [%] = ± Current Matching Current Matching refers to the difference in current from one LED to the next. The ∆I between any two LEDs will meet this requirement. To calculate the error I LED-LED-ERR , first identify the highest and lowest value of the 4 LED currents, and use the formula: I LED-LED-ERR [%] = or which reduces to ± 1x Mode, 1.5x Mode and 2x Mode 1x Mode, 1.5x Mode and 2x Mode all refer to the charge pump configuration. These modes boost the battery input voltage and ensure there is enough voltage at V OUT so that the regulated current will flow through the LEDs and return via the I LED pins. I LED() MEASURED I LED- I LED %100 IMAX IMAX + IMIN -1 100% IMIN IMAX + IMIN -1 100% IMIN 100%IMAX IMINIMAX + Input Current The total input current of the SC604A is a function of the sum of the LED currents, the charge pump mode and the quiescent current. The quiescent current trend is charted on page 12 and used to calculate I IN in the following examples. I IN = IOUT z Mode + I Q = (I LED1+ILED2+ILED3+ILED4 ) z Mode + IQ Example 1: Mode = 1x, I Q = 2.4mA, ILED1+ILED2+ILED3+ILED4 = 4 z 15mA = 60mA Answer 1: I IN = IOUT z Mode + I Q = 60mA z 1 + 2.4mA = 62.4mA Example 2: Mode = 1.5x, I Q = 2.4mA, ILED1+ILED2+ILED3+ILED4 = 4 z 15mA = 60mA Answer 2: I IN = IOUT z Mode + IQ = 60mA z 1.5 + 2.4mA = 92.4mA Mode Transition Voltage Mode transition voltage refers to the input voltage at the point just before the charge pump changes from a weaker mode to a stronger mode. V TRANS1X is the transition from 1x to 1.5x mode, and V TRANS1.5X is the transition from 1.5x to 2x mode. Equations for V TRANS1X and VTRANS1.5X are given on page 7.

 2005 Semtech Corp. www.semtech.com SC604A POWER MANAGEMENT niPe maNniPn oitcnuFniP 1N Ee lbanehgihevitcA

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Td aPlamrehT yllanretnIdetcennoctoN.saivelpitlumgnisuenalpdnuorgottcennoC.sesoprupgniknistaehrofdaP Pin Descriptions ECIVEDE GAKCAP )1( RTLMIA406CS6 1-PLM TRTLMIA406CS )2( 61-PLM BVE406CSd raoBnoitaulavE Notes: (1) Available in tape and reel only. A reel contains 3000 devices. (2) Available in lead-free package only. This product is fully WEEE and RoHS compliant. Ordering InformationPin Configuration Note: (1) The CTRL word must match the outputs in use. TOP VIEW MLPQ16: 4X4 16 LEAD ISET VOUT VIN C1+ ILED1 ILED2 ILED3 ILED4 EN CTRL0 CTRL1 CTRL2 GND C2+ C2- C1- TOP VIEW 16 15 14 13 5678 T

 2005 Semtech Corp. www.semtech.com SC604A POWER MANAGEMENT Block Diagram stupnIlortnoC )1( sutatStuptuO 2LRTC1 LRTC0 LRTC4 DEL3 DEL2 DEL1 DEL

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001 F FOF FON OF FO

100 F FOF FON ON O

101 F FON ON ON O

111 F FOF FOF FOF FO

Table 1 - LED Enable Logic VIN CTRL0 EN VOUT C1+ C2- C2+C1- mAhXLife Fractional Charge Pump [1x, 1.5x, 2x] Schmitt Buffer Schmitt Buffer 250kHz Oscillator & Delay Clk Mode Select [1x, 1.5x, 2x Startup, Shutdown] Current Brightness Control Current Sense FETs and Amplifier(s) Current Set Detect 1.22V Bandgap Voltage GND ISET CTRL1 ILED3 I LED2 I LED1ILED4 CTRL2 Schmitt Buffer Schmitt Buffer Ouput Selection Logic 9 10 11 13 14 15 16 TM Notes: (1) The sequencing of Enable and logic state CTRL{2,1,0} = [1, 1, 1] will affect quiescent state current. I Q = 100µA if Enable transitions high before CTRL{2,1,0} transitions to [1, 1, 1]. I Q = 400µA if Enable transitions high after CTRL{2,1,0} transitions to [1, 1, 1]. If Enable = high and CTRL{2,1,0}= [1, 1, 1] is to be used for an extended period of time, it is recommended that Enable = High when change to the [1, 1, 1] state to ach ieve the lower I Q level.

 2005 Semtech Corp. www.semtech.com SC604A POWER MANAGEMENT Applications Information Designing for Lowest Possible Battery Current The SC604A efficiency and battery current are shown in the plots that follow on page 8. For this example, 4 LEDs are matched at 15mA each. The battery current remains low at 63mA well into the Li-Ion battery range as indicated in the plot by a boundary box. The SC604A uses 1x mode IN=IOUT+IQ) for part of the input voltage range, conserving significant energy from the battery. A similar four (4) output device uses only 1.5x mode (I IN= I OUT z 1.5+IQ) over the input voltage range. This means that the SC604A will have about 25% higher efficiency than a 1.5x only charge pump. Where the competition drops off at 3V, the SC604A uses 2x mode to extend the operating range down to a battery voltage of only 2.85V. The input voltages at which the mode transitions occur are dependent on the forward voltage V F of the LED used and the LED current ILED. To keep the battery current low and in the 1x mode for as long as possible, it is best to choose an LED with a lower V The mode transition voltages V TRANS1X and V TRANS1.5X can be estimated by the following equations: VTRANS1X = V F + V ILED + [(# of LEDs used) z ILED z 1.2] VTRANS1.5X = V F + V ILED + [(# of LEDs used) z ILED z 16] 1.5 where, VF is the forward LED voltage measured from anode to cathode, V ILED is the voltage at the ILED pin, typically VILED = 100mV, I LED is the LED current. Power efficiency can now be estimated for comparison with the intended battery voltage range. Efficiency [%] = Detailed Description The SC604A contains a fractional charge pump, mode selection circuit, output selection logic, current setting detection circuit, and four current sense circuits. All are depicted in the block diagram on page 6. The fractional charge pump multiplies the input voltage a multiple of 1, 1.5 or 2 times the input voltage. The charge pump switches at a fixed 250kHz whenever the mode is 1.5x or 2x. The charge pump does not switch during 1x mode, saving power and improving efficiency. The mode selection circuit automatically selects the mode as 1x, 1.5x or 2x based on circuit conditions such as LED voltage, input voltage and load current. 1x is the most efficient mode, followed by 1.5x and 2x modes. At lower voltages a stronger mode may be needed to maintain regulation, if so, the mode will change first to 1.5x and then to 2x. 2x mode usually operates for a much shorter run time compared to 1x mode, and 2x mode maintains the output until the battery is discharged to 2.85V or less. The LED requiring the highest voltage drop will determine the output voltage needed to drive all outputs with adequate bias. Comparing all cathodes and regulating VOUT for the LED with the lowest cathode voltage ensures sufficient bias for all LEDs. Output selection logic enables control over the LED outputs for on and off functions with eight (8) different output states. The states are defined in Table 1 on page The current set and detection circuit uses an external resistor and a 1.22V reference to program the LED current. Four (4) current regulating circuits sink matched currents from the LEDs. LEDs with matched forward voltage will produce the best possible matched currents. For best matching performance it is recommended that the ∆Vf between LEDs be under 250mV. (For more information on ∆ Vf considerations refer to Semtech application notes). VOUT IOUT 100% VIN (IOUT Mode + IQ

 2005 Semtech Corp. www.semtech.com SC604A POWER MANAGEMENT Efficiency Comparison for 4 LEDs with 15mA Each and LED = 3.5V 100 VIN [V] Efficiency [%] Competition 1.5x mode Se mte ch 1x mode 90% of Li-Ion battery life Semtech 1.5x mode Battery Current Comparison for 4 LEDs at 15mA Each with LED = 3.5V 100 110 VIN [V] Battery Current [mA] 90% of Li-Ion battery life Competition 1.5x mode Se mte ch 1x mode Semtech 1.5x mode

 2005 Semtech Corp. www.semtech.com SC604A POWER MANAGEMENT There are four methods for setting and adjusting the LED current outlined here. The methods are: 1) RSET only 2) Analog Reference VADJ 3) NMOS switched parallel resistors 4) PWM Input Method 1. The most basic means of setting the LED current is with a resistor connected from ISET to GND, as shown in the application circuit on Page 1. The resistor R SET establishes the reference current needed for a constant LED current. Values of R SET for a fixed LED current are given in Table 2 and also in the below graph, “Typical RSET Resistance vs. LED Current”. Methods 2 and 3 on page 10 are for setting the LED current allow for brightness control. Table 2 - Resistor Value Selection RRRRR TESTES TES TESTES eulaVe ulaV eulaV eulaVe ulaV ]Am[DELI] Am[DELI ]Am[DELI ]Am[DELI] Am[DELIR RRRR TESTES TES TESTES k[k[k[k[k[ ΩΩΩΩΩ ]]]]] ktseraeNk tseraeN ktseraeN ktseraeNk tseraeN ΩΩΩΩΩ dradnatSd radnatS dradnatS dradnatSd radnatS eulaVe ulaV eulaV eulaVe ulaV dradnatSd radnatS dradnatS dradnatSd radnatS eulaVe ulaV eulaV eulaVe ulaV ecnereffiD%e cnereffiD% ecnereffiD% ecnereffiD%e cnereffiD% 5.01 391 39% 0.0 11 740 74% 2.0- 27 327 32% 0.0 35 514 51% 6.0- 50 .491 .39% 0.1- 015 .745 .74% 0.0 020 .420 .42% 0.0 035 .615 .61% 0.0 Methods for Setting LED Current Typical RSET Resistance vs. LED Current 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 1000 LED Current [mA] RSET Resistance [kΩ]

 2005 Semtech Corp. www.semtech.com SC604A POWER MANAGEMENT V JDA ]V[I DEL ]Am[V JDA ]V[I DEL ]Am[ 000.02 .030 06.08 .41 001.07 .720 07.03 .21 002.01 .520 08.07 .9 003.05 .220 09.01 .7 004.00 .020 00.11 .2 005.03 .710 51.10 .1 Table 3 - Analog Voltage for LED Current Control Figure 1 - Analog Voltage for LED Current Control Figure 2 - 3 Bit LED Current Control with Open Drain Method 2. The example circuit in Figure 1 uses a 16.5kΩ resistor and an analog input DC voltage, VADJ , which varies from 1.2V to 0V to control LED current from 1mA to 30mA. Table 3 shows the resulting output. If necessary, the analog V ADJ voltage can be sourced from a voltage higher than 1.2V, but the source must be divided down so that the V ADJ mode will not exceed 1.2V. For lower current applications and for higher resolution, a larger resistor may be substituted in this circuit. PWM applications are also possible with this circuit by application of RC filtering. (Consult with Semtech for detailed application support). Methods for Setting LED Current (Cont.) Method 3. The circuit in Figure 2 uses open drain NMOS transistors to set an equivalent resistance for RSET. Parallel combinations are switched on and off for R1, R2 and R3. R4 is always connected, so that a minimum value of LED current can be maintained at 1.5mA.

 2005 Semtech Corp. www.semtech.com SC604A POWER MANAGEMENT OVP Event with LED Open Circuit Mode Transition Voltage vs. LED Voltage Startup with 4 LEDs at 20 mA Efficiency vs. Load at Low BatteryEfficiency vs. Load at High Battery Quiescent Current Trend Typical Characteristics 100 02 0 4 0 6 0 8 0 1 0 0 1 2 0 Total Load Current [mA] Efficiency [%] VIN = 3.8V VIN = 4.0V VIN = 4.2V 100 0 2 04 06 08 0 1 0 0 1 2 0 Total Load Current [mA] Efficiency [%] VIN = 3.6V VIN = 2.8V VIN = 3.4V 0 20 40 60 80 100 120 Total Output Current [mA] Quiescent Current [mA] Trend for 4 LEDs 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 0 5 10 15 20 25 30 35 LED Current [mA] Input Voltage [V] Vf = 3.6V Vf = 3.4V Vf = 3.2V 1X to 1.5X Mode for 4 LEDs

 2005 Semtech Corp. www.semtech.com SC604A POWER MANAGEMENT Battery Current for 4 LEDs at 0.5mA Efficiency for 4 LEDs at 0.5mA Efficiency for 4 LEDs at 20mA Battery Current for 4 LEDs at 10mA Efficiency for 4 LEDs at 10mA Battery Current for 4 LEDs at 20mA Typical Characteristics with 4 LEDs 100 Input Voltage [V] Efficiency [%] LED = 3.37V Input Voltage [V] Battery Current [mA] LED = 3.37V 100 Input Voltage [V] Efficiency [%] LED = 3.45V 100 120 140 Input Voltage [V] Battery Current [mA] LED = 3.45V 1.5 2.5 3.5 Input Voltage [V] Battery Current [mA] LED = 2.91V LED = 2.91V Input Voltage [V] Efficiency [%]

 2005 Semtech Corp. www.semtech.com SC604A POWER MANAGEMENT Typical Characteristics with 4 LEDs Ripple in 1x Mode for 4 LEDs at 20mA Each Ripple in 1.5x Mode for 4 LEDs at 20mA Each Ripple in 2x Mode for 4 LEDs at 20mA Each

 2005 Semtech Corp. www.semtech.com SC604A POWER MANAGEMENT Evaluation Board Schematic 1.0uF 1 2 1.0uF 1 2 RSET TBD 1 2 D4 12 D3 12 D2 12 D1 12 1.0uF1 1ohm 1 2 1ohm 1 2 1ohm 1 2 1ohm 1 2 CNTRL1 CNTRL0 JP4 JP3 JP2 JP1 SC604 EN 1 CTRL0 2 CTRL1 3 CRTL2 4 ISET5 VOUT6 C2+11 GND12 ILED413 ILED314 ILED215 ILED116 C2-10 VIN7 C1-9 C1+8 JP6 ENABLE C2+ C2- C1- C1+ R4+ 1 R4- 1 R3+ 1 R3- 1 R2+ 1 LED4 1 R2- 1 LED3 1 LED2 1 R1+ 1 LED1 1 OFF ON R1- 1 BATTERY + VBAT 1 BATTERY - GND 1 CTRL2 1 RIN 0.22 1 2 CTRL1 1 CTRL0 1 CNTRL2 JP5 Input Resistance By pass 1 2 Input Jacks POS 1 NEG2 VBAT BATTERY - GND 1 ENABLE LOWLOWLOW HIGHHIGHHIGH C1- 10uF1 VBAT VOUT JP7 Connect RSET pot. 1 2 POT_3296W-105 1 3 VOUT RSET 1.0uF1 Analog Control VADJ 1 C1+ RADJ 16.5k 1 2 C2- C2+

Evaluation Board Bill of Materials Evaluation Board Gerber Plots Reference Value Comment U1 SC604A Component references in bold are the only essential design components. C1,C2,C3,C4 1.OµF Bucket, input and output capacitors. Ceramic, low ESR type, 6.3V rating or higher. C6 10µF This extra capacitor supports usage of long power leads from benchtop supply. D1,D2,D3,D4 - Add LEDs to meet the requirements of the application. J1, J2, J3, J4 - Jumpers in series with each LED. JP1,JP2,JP3,JP4 - Jumpers to bypass each 1Ω sense resistor and bypass J1, J2, J3 and J4. JP5 - Jumper for bypassing the R4 input resistor. JP6 - Enable jumper. JP7 - Connects RSET potentiometer. Remove this jumper when using a fixed value R1. CTRL0,CTRL1,CTRL2 - Jumpers provide High/Low settings for the control bits. RSET - RSET resistor 3296W-105 Evaluation board has 1MΩ potentiometer in place of R1. R4 0.22 Ω Series input resistor for studying effects of input resistance. RADJ 16.5kΩ Resistor for analog brightness control. Apply test signal of 0 to 1.2V at VADJ test point. J5 - Banana jacks for power supply. Top View Bottom View SC604A 16 2005 Semtech Corp. www.semtech.com POWER MANAGEMENT

 2005 Semtech Corp. www.semtech.com SC604A POWER MANAGEMENT Outline Drawing- MLP-16 [4x4] .003 .010 .074 .012 .085 .000 .031 (.008) 0.08 0.30 .014 .089 0.25 1.90 .040 .002 0.00 0.80 2.25 0.35 2.15 0.05 1.00 (0.20) .004 0.10 1.90 2.15 2.25 0.65 BSC.026 BSC .089.085.074 D/2 A LxN bbb C A B bxN e SEATING PLANE C E/2 N e/2 aaa C CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). COPLANARITY APPLIES TO THE EXPOSED PAD AS WELL AS THE TERMINALS. NOTES: A D E B INCHES N bbb aaa DIM L e E D A b MIN MAX MILLIMETERS MINMAX NOM INDICATOR (LASER MARK) PIN 1 DIMENSIONS NOM yyww = Datecode (Example: 0452) Marking Information 604A yyww

 2005 Semtech Corp. www.semtech.com SC604A POWER MANAGEMENT Land Pattern MLP-16pin [4x4] P Y K C Z P Y X G K H .189 .026 .016 .041 .106 .091 .091 4.80 0.40 1.05 0.65 2.30 2.30 2.70 DIM (3.75) MILLIMETERS DIMENSIONS (.148) INCHES THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY. CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR COMPANY'S MANUFACTURING GUIDELINES ARE MET. NOTES: 2x GH2x (C) 2x Z X Semtech Corporation Power Management Products Division

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