SC652

SC652 SEMTECH | Alldatasheet

Document overview

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Technical content

Features

Input supply voltage range — 2.9V to 5.5V Charge pump modes — 1x, 1.5x and 2x PWM dimming control with low pass fi lter provides DC backlight current (not pulsed) PWM frequency range — 200Hz to 50kHz Five adjustable current sinks — 500μA to 25mA Backlight current accuracy ±1.5% typical Backlight current matching ±0.5% typical LED fl oat detection Charge pump frequency — 250kHz Low shutdown current — 0.1μA typical Ultra-thin package — 2 x 2 x 0.6(mm) Fully WEEE and RoHS compliant

Applications

Cellular phones, smart phones, and PDAs LCD display modules Portable media players Digital cameras Personal navigation devices Display/keypad backlighting and LED indicators

Description

The SC652 is a high effi ciency charge pump LED driver using Semtech’s proprietary charge pump technology. Performance is optimized for use in single-cell Li-ion battery applications. The device provides backlight current using up to five matched current sinks. The load and supply conditions determine whether the charge pump operates in 1x, 1.5x, or 2x mode. The maximum current per LED is set by a resistor (R ISET ) connected from the ISET pin to the input voltage. The current can be set between 500μA and 25mA. This current can be varied by applying a pulse-width modulated (PWM) signal to the EN/PWM pin. A low-pass filter is used to develop a DC current level rather than a pulsed current output, resulting in a more effi cient system. The resulting DC current in each LED (I BL) is equal to the maximum current setting multiplied by the duty cycle of the PWM control signal. Using this control system, I BL can gradually fade between levels. With a 2 x 2 (mm) package and 4 small capacitors, the SC652 provides a complete LED driver solution with a minimal PCB footprint. SC652 IN EN/PWM GND OUT BL1 ISET CIN 2.2μF C1+ PWM Signal COUT 2.2μF BL2 BL3 BL4 C2+C1- C2- RISET BL5 2.2μF 2.2μF VBAT = 2.9V to 5.5V US Patents: 6,504,422; 6,794,926 Typical Application Circuit March 13, 2009

Ordering Information

SC652ULTRT(1)(2) MLPQ-UT-14 2×2 SC652EVB Evaluation Board Notes: (1) Available in tape and reel only. A reel contains 3,000 devices. (2) Lead-free package only. Device is WEEE and RoHS compliant. TOP VIEW1 3 8 45 6 7 14 13 12 11 OUT GND BL5 C2+ ISET IN C1+ C1- C2- BL1 BL2 EN/ PWM BL4 BL3 AD yw MLPQ-UT-14; 2x2, 14 LEAD θJA = 127°C/W AD = Marking code yw = Date Code

Exceeding the above specifi cations may result in permanent damage to the device or device malfunction. Operation outside of the parameters specifi ed in the Electrical Characteristics section is not recommended. NOTES: (1) Tested according to JEDEC standard JESD22-A114-B. (2) ΔV F(max) = 1.0V when VIN = 2.9V, higher VIN supports higher ΔVF(max) (3) Calculated from package in still air, mounted to 3 x 4.5(in), 4 layer FR4 PCB per JESD51 standards. Absolute Maximum Ratings Unless otherwise noted, TA = +25°C for Typ, -40°C to +85°C for Min and Max, TJ(MAX) = 125°C, VIN = 3.7V, CIN= COUT = C1= C2= 2.2μF, (ESR = 0.03Ω), 500μA < IFS_BL < 25mA, Duty Cycle of PWM = 100%, All 5 LEDs connected and enabled. Parameter Symbol Conditions Min Typ Max Units Shutdown Current I Q(OFF) TA = 25°C 0.1 2 μA Quiescent Current I Q Charge pump in 1x mode, 2.9V < VIN < 4.2V, 5 LEDs enabled 1.5 mACharge pump in 1.5x mode, 2.9V < VIN < 4.2V, 5 LEDs enabled 2 Charge pump in 2x mode, 2.9V < VIN < 4.2V, 5 LEDs enabled 2.5 Maximum Total Output Current I OUT(MAX) VIN > 3.0V, sum of all active LED currents, VOUT(MAX) = 4.2V 125 mA Backlight Current Setting (1) IFS_BL PWM duty cycle = 100%, 200kΩ ≥ RISET ≥ 4kΩ 0.5 25 mA Current Gain I GAIN Gain from IISET to IFS_BL 100 A/A Current Set Voltage V IN - ISET Voltage across RISET 1V Backlight Current Matching (2) IBL-BL IFS_BL = 12mA, Duty = 100% -3.5 ±0.5 +3.5 % Backlight Current Accuracy I BL_ACC IFS_BL = 12mA, Duty = 100% ±1.5 % PWM Input Frequency fEN/PWM Guaranteed by design 0.2 50 kHz EN/PWM Minimum High Time tHIGH_MIN (3) 1μ s

Electrical Characteristics

Recommended Operating Conditions Voltage Diff erence between any two LEDs (V) . . . ΔV F ≤ 1.0(2) Thermal Information Thermal Resistance, Junction to Ambient(3) (°C/W) . . . 127

Parameter Symbol Conditions Min Typ Max Units Current Transition Settling Time ts Duty cycle change from 100% to 50%(1)(4) 0.5 s EN/PWM Low Time tLT Time that voltage on the EN/PWM pin can be low without disabling the device 5m s 1x Mode to 1.5x Mode Falling Transition Voltage VTRANS1x IOUT = 50mA, IBLn = 10mA, VOUT = 3.2V 3.25 V 1.5x Mode to 1x Mode Hysteresis VHYST1x IOUT = 50mA, IBLn = 10mA, VOUT = 3.2V 300 mV 1.5x Mode to 2x Mode Falling Transition Voltage VTRANS1.5x IOUT = 50mA, IBLn = 10mA, VOUT = 4.0V(5) 2.9 V 2x Mode to 1.5x Mode Hysteresis V HYST1.5x IOUT = 50mA, IBLn = 10mA, VOUT = 4.0V(5) 500 mV Current Sink Off -State Leakage Current IBLn(off ) VIN = VBLn = 4.2V 0.1 1 μA Charge Pump Frequency f PUMP VIN = 3.2V 250 kHz Output Short Circuit Current Limit IOUT(SC) OUT pin shorted to GND 45 mA VOUT > 2.5V 400 Under Voltage Lockout Threshold V UVLO-OFF Increasing VIN — lockout released 2.4 V UVLO Hysteresis V UVLO-HYS 500 mV Over-Voltage Protection V OVP OUT pin open circuit, VOUT = VOVP — rising threshold 5.7 6.0 V Over-Temperature T OT Rising Temperature 165 °C OT Hysteresis TOT-HYS 25 °C Input High Threshold (6) VIH VIN = 5.5V 1.4 V Input Low Threshold (6) VIL VIN = 2.9V 0.4 V Input High Current (6) IIH VIN = 5.5V 1 μA Input Low Current (6) IIL VIN = 5.5V 1 μA Electrical Characteristics (continued) Notes: (1) Guaranteed by design (2) Current matching equals ± [I BL(MAX) - IBL(MIN] / [IBL(MAX) + IBL(MIN)]. (3) t HIGH_MIN is the minimum time needed for accurate PWM sampling. (4) The settling time is aff ected by the magnitude of change in the PWM duty cycle. (5) Test voltage is V OUT = 4.0V — a relatively extreme LED voltage used to force a transition during test. Typically VOUT = 3.2V for white LEDs. (6) Applied to EN/PWM pin.

Backlight Accuracy (5 LEDs) — 12mA Each Backlight Accuracy (5 LEDs) — 0.5mA Each Backlight Accuracy (5 LEDs) — 25mA Each V IN(V) Backlight Accuracy (%) MAX LED MIN LED VOUT = 3.64V, IOUT = 125mA, 25°C Backlight Matching (5 LEDs) — 12mA Each Backlight Matching (5 LEDs) — 0.5mA Each Backlight Matching (5 LEDs) — 25mA Each VOUT = 3.50V, IOUT = 60mA, 25°C VIN (V) Backlight Accuracy (%) MAX LED MIN LED VOUT = 3.09V, IOUT = 2.5mA, 25°C VIN (V) Backlight Accuracy (%) MAX LED MIN LED VOUT = 3.64V, IOUT = 125mA, 25°C Backlight Matching (%) VOUT = 3.50V, IOUT = 60mA, 25°C VIN (V) Backlight Matching (%) VIN (V) Backlight Matching (%) VOUT = 3.09V, IOUT = 2.5mA, 25°C

Typical Characteristics (continued) Backlight Effi ciency (5 LEDs) — 12mA Each Backlight Effi ciency (5 LEDs) — 5.0mA Each Backlight Effi ciency (5 LEDs) — 25mA Each 100 VIN (V) Efficiency (%) VOUT = 3.64V, IOUT = 125mA, 25°C Battery Current (5 LEDs) — 12mA Each Battery Current (5 LEDs) — 5.0mA Each Battery Current (5 LEDs) — 25mA Each 100 120 140 160 180 200 V IN (V) Battery Current (mA) VOUT = 3.64V, IOUT = 125mA, 25°C 100 VIN(V) Efficiency (%) VOUT = 3.50V, IOUT = 60mA, 25°C 100 Battery Current (mA) VOUT = 3.50V, IOUT = 60mA, 25°C VIN (V) Battery Current (mA) VOUT = 3.35V, IOUT = 25mA, 25°C 100 VIN (V) Efficiency (%) VOUT = 3.35V, IOUT = 25mA, 25°C

Ripple — 1X Mode VIN (100mV/div) VIN=4.2V, RISET = 4kΩ, 5 Backlights — 25 mA each, 25°C (see note 1) Time (10μs/div) VOUT (100mV/div) Ripple — 1.5X Mode VIN (100mV/div) VIN=3.2V, RISET = 4kΩ, 5 Backlights — 25 mA each, 25°C (see note 1) Time (10μs/div) VOUT (100mV/div) Ripple — 2X Mode VIN (100mV/div) VIN=2.9V, RISET = 4kΩ, 5 Backlights — 25 mA each, 25°C (see note 1) Time (10μs/div) VOUT (100mV/div) Typical Characteristics (continued) NOTE 1: CIN = COUT = 4.7μF — 0603 size (1608 metric); C1 = C2 = 2.2μF — 0402 size (1005 metric) NOTE 2: CIN = COUT= C1 = C2 = 2.2μF — 0603 size (1608 metric) Ripple — 1X Mode VIN (100mV/div) VIN=4.2V, RISET = 5.56kΩ, 5 Backlights — 18 mA each, 25°C (see note 2) Time (10μs/div) VOUT (100mV/div) Ripple — 1.5X Mode VIN (100mV/div) VIN=3.2V, RISET = 5.56kΩ, 5 Backlights — 18 mA each, 25°C (see note 2) Time (10μs/div) VOUT (100mV/div) Ripple — 2X Mode VIN (100mV/div) VIN=2.9V, RISET = 5.56kΩ, 5 Backlights — 18 mA each, 25°C (see note 2) Time (10μs/div) VOUT (100mV/div)

Typical Characteristics (continued) PWM Accuracy — 4.2V VIN = 4.2V, RISET = 4.99kΩ, Calculated IBL = (100/RISET) x Duty Cycle Calculated IBL (mA) Measured IBL (mA) 32kHz 04 81 2 1 6 2 0 50kHz 200Hz PWM Accuracy — 3.7V PWM Accuracy — 2.9V Calculated IBL (mA) Measured IBL (mA) VIN = 3.7V, RISET = 4.99kΩ, Calculated IBL = (100/RISET) x Duty Cycle 04 81 2 1 6 2 0 32kHz 50kHz 200Hz Measured IBL (mA) Calculated IBL (mA) VIN = 2.9V, RISET = 4.99kΩ, Calculated IBL = (100/RISET) x Duty Cycle 04 8 12 16 20 32kHz 50kHz 200Hz Percentage of Maximum IBL — 4.2V PWM Duty Cycle (%) Percentage of Maximum IBL (%) VIN = 4.2V, RISET = 4.99kΩ 100 0 20 40 60 80 100 200Hz 32kHz 50kHz VIN = 3.7V, RISET = 4.99kΩ Percentage of Maximum IBL (%) PWM Duty Cycle (%) 100 0 20 40 60 80 100 200Hz 32kHz 50kHz VIN = 2.9V, RISET = 4.99kΩ Percentage of Maximum IBL (%) PWM Duty Cycle (%) 100 0 20 40 60 80 100 200Hz 50kHz 32kHz Percentage of Maximum IBL — 3.7V Percentage of Maximum IBL — 2.9V

Typical Characteristics (continued) Start-up — 0% to 50% IBL (10.0mA/div) VIN = 3.7V, 0 to 50% duty cycle, RISET = 4.99kΩ, fPWM = 32kHz Time (200ms/div) VPWM (2V/div) 0mA— 10mA 50% 0V— Start-up — 0% to 100% IBL (10.0mA/div) VIN = 3.7V, 0 to 100% duty cycle, RISET = 4.99kΩ, no PWM Time (200ms/div) VPWM (2V/div) 0mA— 20mA 100%0V— DC Backlight Current — 32kHz PWM IBL (10.0mA/div) VIN = 3.7V, 50% duty cycle, RISET = 4.99kΩ, IBL = 10mA Time (20μs/div) VPWM (2V/div) 0mA— 0V— DC Backlight Current — 200Hz PWM IBL (10.0mA/div) VIN = 3.7V, 50% duty cycle, RISET = 4.99kΩ, IBL = 10mA Time (1ms/div) VPWM (2V/div) 0mA— 0V— IBL Settling Time — 50% to 100% IBL (10.0mA/div) VIN = 3.7V, RISET = 4.99kΩ, fPWM = 32kHz Time (200ms/div) VPWM (2V/div) 0mA— 20mA 50%0V— 10mA 100% IBL Settling Time — 100% to 50% IBL (10.0mA/div) VIN = 3.7V, RISET = 4.99kΩ, fPWM = 32kHz Time (200ms/div) VPWM (2V/div) 0mA— 20mA 50% 0V— 10mA 100%

Pin # Pin Name Pin Function

1 OUT Charge pump output — all LED anode pins should be connected to this pin

2 IN Battery voltage input

3 ISET Current setting pin — connect a resistor between this pin and the IN pin to set the LED current

4 EN/PWM Enable pin — also used as the PWM input for dimming control

5 BL5 Current sink output for main backlight LED 5 — leave this pin open if unused

6 BL4 Current sink output for main backlight LED 4 — leave this pin open if unused

7 BL3 Current sink output for main backlight LED 3 — leave this pin open if unused

8 BL2 Current sink output for main backlight LED 2 — leave this pin open if unused

9 BL1 Current sink output for main backlight LED 1 — leave this pin open if unused

10 GND Ground pin

11 C2- Negative connection to bucket capacitor 2

12 C1- Negative connection to bucket capacitor 1

13 C1+ Positive connection to bucket capacitor 1

14 C2+ Positive connection to bucket capacitor 2

(1x, 1.5x, 2x) C1+ C1- C2+ C2- OUT BL1 BL2 BL3 BL4 VIN IN EN/ PWM VOUT GND 13 111412 ISET 3 BL55

This design is optimized for handheld applications sup- plied from a single Li-Ion cell and includes the following key features: A high effi ciency fractional charge pump that supplies power to all LEDs Five matched current sinks that control LED backlighting current, providing 500μA to 25mA per LED EN/PWM pin functions as an enable and pro- vides PWM control of the LED brightness High Current Fractional Charge Pump The backlight outputs are supported by a high effi ciency, high current fractional charge pump output. The charge pump multiplies the input voltage by 1, 1.5, or 2 times. The charge pump switches at a fi xed frequency of 250kHz in 1.5x and 2x modes and is disabled in 1x mode to save power and improve effi ciency. 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. The 1x mode is the most effi cient of the three modes, followed by 1.5x and 2x modes. Circuit conditions such as low input voltage, high output current, or high LED voltage place a higher demand on the charge pump output. A higher numerical mode (1.5x or 2x) may be needed momentarily to maintain regulation at the OUT pin during intervals of high demand. The charge pump responds to momentary high demands, setting the charge pump to the optimum mode to deliver the output voltage and load current while optimizing efficiency. Hysteresis is provided to prevent mode toggling. The charge pump requires two bucket capacitors for proper operation. One capacitor must be connected between the C1+ and C1- pins and the other must be con- nected between the C2+ and C2- pins as shown in the Typical Application Circuit diagram. These capacitors should be equal in value, with a minimum capacitance of 1μF to support the charge pump current requirements. The device also requires at least 1μF capacitance on the IN pin and at least 1μF capacitance on the OUT pin to mini- mize noise and support the output drive requirements of IOUT up to 90mA. For output currents higher than 90mA, a nominal value of 4.7μF is recommended for COUT and CIN. Capacitors with X7R or X5R ceramic dielectric are strongly recommended for their low ESR and superior temperature and voltage characteristics. Y5V capacitors should not be used as their temperature coeffi cients make them unsuitable for this application. It is important that the minimum value of the capacitors used is no lower than 1μF. This may require the use of 2.2μF capacitors to be sure that the degradation of capacitance due to DC voltage does not cause the capacitance to go below 1μF. LED Backlight Current Sinks The full scale backlight current (I FS_BL ) is set via the current through the ISET pin (I ISET ). IFS_BL is regulated to the value of IISET multiplied by an internal gain of 100A/A. RISET is used to control the current through the ISET pin. The relationship between R ISET and the full scale back- light current is: RISET = 100/IFS_BL All backlight current sinks have matched currents, even when there is a variation in the forward voltages (ΔV F ) of the LEDs. A ΔV F of 1.0V is supported when the input voltage is at 2.9V. Higher ΔV F LED mis-match is sup- ported when V IN is higher than 2.9V. All current sink outputs are compared and the lowest output is used for setting the voltage regulation at the OUT pin. This is done to ensure that suffi cient bias exists for all LEDs. Any unused outputs must be left open and unused LED drivers will remain disabled. PWM Operation A PWM signal can be used to adjust the DC current through the LEDs. When the duty cycle is 100%, the backlight current through each LED (I BL) equals the full scale current set by RISET. As the duty cycle decreases, the EN/PWM input samples the control signal and converts the duty cycle to a DC current level. In conventional PWM controlled systems, the output current pulses on and off with the PWM input to achieve an effective Applications Information

Applications Information (continued) average current. Providing a DC current through the LEDs instead of a pulsed current provides an effi ciency advantage over other PWM controlled systems by allow- ing the charge pump to remain in 1x mode longer because the maximum current is equal to the average current. PWM Sampling The sampling system that translates the PWM signal to a DC current requires the EN/PWM pin to have a minimum high time t HIGH_MIN to set the DC level. High time less than tHIGH_MIN impacts the accuracy of the target IBL. The minimum duty cycle needed to support the minimum high time specifi cation varies with the applied PWM frequency (see fi gure 1). Note that use of a lower PWM frequency, from 200Hz to 10kHz, will support lower minimum duty cycle and an extended backlight dimming range. 01 02 0 30 40 50 PWM Fre quency (kHz) Minimum Duty Cycle (%) tHIGH_MIN = 1μs Figure 1 — Minimum Duty Cycle Shutdown Mode The device is disabled when the EN/PWM pin is held low for 7ms or longer. Protection Features The SC652 provides several protection features to safe- guard the device from catastrophic failures. These features include: Output Open Circuit Protection Over-Temperature Protection Charge Pump Output Current Limit LED Float Detection Output Open Circuit Protection Over-Voltage Protection (OVP) at the OUT pin prevents the charge pump from producing an excessively high output voltage. In the event of an open circuit between the OUT pin and all current sinks (no loads connected), the charge pump runs in open loop and the voltage rises up to the OVP limit. OVP operation is hysteretic, meaning the charge pump will momentarily turn off until V OUT is suffi ciently reduced. The maximum OVP threshold is 6.0V, allowing the use of a ceramic output capacitor rated at 6.3V. Over-Temperature Protection The Over-Temperature (OT) protection circuit prevents the device from overheating and experiencing a cata- strophic failure. When the junction temperature exceeds 165 °C, the device goes into thermal shutdown with all outputs disabled until the junction temperature is reduced. All register information is retained during thermal shutdown. Hysteresis of 20°C is provided to ensure that the device cools sufficiently before re-enabling. Charge Pump Output Current Limit The device limits the charge pump current at the OUT pin. If the OUT pin is shorted to ground, or V OUT is lower than 2.5V, the typical output current limit is 45mA. The typical output current is limited to 400mA when over loaded resistively with V OUT greater than 2.5V. LED Float Detection Float detect is a fault detection feature of the LED back- light outputs. If an output is programmed to be enabled and an open circuit fault occurs at any backlight output, that output will be disabled to prevent a sustained output OVP condition from occurring due to the result- ing open loop. Float detect ensures device protection but does not ensure optimum performance.

.020 .006 .010 .000 .077 N aaa bbb L e D E b .012 .016 BSC .004 .003 .008 (.006) .079 MINDIM NOM INCHES - 0.600.50

0.40 BSC

(0.152) 0.25 0.10 0.08 0.30 0.15 1.95 0.00 0.20 2.00 0.35 0.25 2.05 0.05 NOM MILLIMETERS MIN MAX bxN 0.20 0.15 NOTES: CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES).1. PIN 1 INDICATOR (LASER MARK) A B aaa C C SEATING PLANE bbb C A B N D E A e/2 e E/2 D/2 .010 MAX DIMENSIONS .014 .002 .024 .081 A - LxN Outline Drawing — MLPQ-UT-14 2x2

Power Management Products Division

200 Flynn Road, Camarillo, CA 93012

Phone: (805) 498-2111 Fax: (805) 498-3804 www.semtech.com Contact Information SC652 Land Pattern — MLPQ-UT-14 2x2 MILLIMETERSDIM INCHES (.079) X Y Z G C P .008 .102 .024 .016 .055 0.40 0.20 1.40 (2.00) 2.60 0.60 DIMENSIONS SQUARE PACKAGE - DIMENSIONS APPLY IN BOTH " X " AND " Y " DIRECTIONS. CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY. CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR COMPANY'S MANUFACTURING GUIDELINES ARE MET. NOTES: Y P (C) G X 4. PIN 1 PAD CAN BE SHORTER THAN THE ACTUAL PACKAGE LEAD TO AVOID SOLDER BRIDGING BETWEEN PINS 1 & 14. R .004 0.10 R Z