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1.5 A LED Flash Driver with

C-Compatible Interface

ADP1650

Rev. C

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FEATURES

Ultracompact solution

Small, 2 mm × 1.5 mm, 12-ball WLCSP package

Thin, 3 mm × 3 mm × 0.75 mm, 10-lead LFCSP package

Smallest footprint, 1 mm height, 1 H power inductor

LED current source for local LED grounding

Simplified routing to/from LED

Improved LED thermals

Synchronous 3 MHz PWM boost converter, no external diode

High efficiency: 90% peak

Reduces high levels of input battery current during flash

Limits battery current drain in torch mode

C programmable

Currents up to 1500 mA in flash mode for 1 LED with

±7% accuracy over all conditions

Currents up to 200 mA in torch mode

Programmable dc battery current limit (4 settings)

Programmable flash timer up to 1600 ms

Low VBAT mode to reduce LED current automatically

4-bit ADC for LED V

, die/LED temperature readback

Control

C-compatible control registers

External STROBE and torch input pins

2 transmitter mask (TxMASK) inputs

Safety

Thermal overload protection

Inductor fault detection

LED short-/open-circuit protection

APPLICATIONS

Camera-enabled cellular phones and smart phones

Digital still cameras, camcorders, and PDAs

FUNCTIONAL BLOCK DIAGRAM

08837-001

ADP1650

10µF

1.0µH

INPUT VOLTAGE = 2.7V TO 5.0

VOUT

PGND

STROBE

10µF

LED_OUT

EN SGND

SCL

SDA

TX1/TORCH

X2/ILED/ADC

GPIO1

GPIO2

MAX 1.5A

VIN

Figure 1.

8837-002

DIGITAL

INPUT/

OUTPUT

Li-ION +

PGND

INDUCTOR

LED

ANODE

AREA = 16.4mm

Figure 2. PCB Layout (WLCSP)

GENERAL DESCRIPTION

The ADP1650 is a very compact, highly efficient, single white

LED flash driver for high resolution camera phones that

improves picture and video quality in low light environments.

The device integrates a programmable 1.5 MHz or 3 MHz

synchronous inductive boost converter, an I

C-compatible

interface, and a 1500 mA current source. The high switching

frequency enables the use of a tiny, 1 mm high, low cost, 1 µH

power inductor, and the current source permits LED cathode

grounding for thermally enhanced, low EMI, and compact

layouts.

The LED driver maximizes efficiency over the entire battery

voltage range to maximize the input-power-to-LED-power

conversion and to minimize battery current draw during flash

events. A programmable dc battery current limit safely maximizes

LED current for all LED V

and battery voltage conditions.

Two independent TxMASK inputs permit the flash LED current

and battery current to reduce quickly during a power amplifier

current burst. The I

C-compatible interface enables the pro-

grammability of timers, currents, and status bit readback for

operation monitoring and safety control.

The ADP1650 is available in a compact 12-ball, 0.5 mm pitch

WLCSP package and a 10-lead LFCSP package, and operates

within specification over the full −40°C to +125°C junction

temperature range.

Summary of content (32 pages)

PAGE 1
.5 A LED Flash Driver with I2C-Compatible Interface ADP1650 FEATURES APPLICATIONS Camera-enabled cellular phones and smart phones Digital still cameras, camcorders, and PDAs FUNCTIONAL BLOCK DIAGRAM INPUT VOLTAGE = 2.7V TO 5.0V 10µF 1.0µH TX1/TORCH VIN GPIO1 SW VOUT TX2/ILED/ADC GPIO2 10µF ADP1650 STROBE LED_OUT MAX 1.5A SCL SGND PGND 08837-001 SDA EN Figure 1. Li-ION + C1 L1 PGND Li-ION + C2 INDUCTOR DIGITAL INPUT/ OUTPUT AREA = 16.
PAGE 2
ADP1650 TABLE OF CONTENTS Features .............................................................................................. 1 Indicator LED Driver................................................................. 14 Applications....................................................................................... 1 Low Battery LED Current Foldback ........................................ 14 Functional Block Diagram ..............................................................
PAGE 3
ADP1650 SPECIFICATIONS VIN 1 = 3.6 V, TJ = −40°C to +125°C for minimum/maximum specifications, and TA = 25°C for typical specifications, unless otherwise noted. Table 1. Parameter 2 SUPPLY Input Voltage Range Undervoltage Lockout Threshold Undervoltage Lockout Hysteresis Shutdown Current (IQ), EN = 0 V Standby Current (ISTBY), EN = 1.
PAGE 4
ADP1650 Parameter 2 Pass-Through Mode Transition, Flash VIN to LED_OUT, Entry VIN to LED_OUT, Exit Pass-Through Mode Transition, Torch VIN to LED_OUT, Entry VIN to LED_OUT, Exit DIGITAL INPUTS/GPIO Input Logic Low Voltage Input Logic High Voltage GPIO1, GPIO2, STROBE Pull-Down Torch Glitch Filtering Delay INDICATOR LED LED Current Accuracy Short-Circuit Detection Threshold Open-Circuit Detection Threshold ADC Resolution Error Input Voltage Range, GPIO2 SAFETY FEATURES Maximum Timeout For Flash Timer Accura
PAGE 5
ADP1650 RECOMMENDED SPECIFICATIONS: INPUT AND OUTPUT CAPACITANCE AND INDUCTANCE Table 2. Parameter CAPACITANCE Input Output MINIMUM AND MAXIMUM INDUCTANCE Symbol CMIN L Conditions Min Typ Max Unit TA = −40°C to +125°C TA = −40°C to +125°C TA = −40°C to +125°C 4.0 3.0 0.6 10 10 1.0 20 1.5 μF μF μH I2C-COMPATIBLE INTERFACE TIMING SPECIFICATIONS Table 3. Parameter 1 fSCL tHIGH tLOW tSU, DAT tHD, DAT tSU, STA tHD, STA tBUF tSU, STO tR tF tSP CB 2 2 Max 400 0.6 1.3 100 0 0.6 0.6 1.3 0.6 20 + 0.
PAGE 6
ADP1650 ABSOLUTE MAXIMUM RATINGS THERMAL RESISTANCE Table 4. Parameter VIN, SDA, SCL, EN, GPIO1, GPIO2, STROBE, LED_OUT, SW, VOUT to Power Ground PGND to SGND Ambient Temperature Range (TA) Junction Temperature Range (TJ) Storage Temperature ESD Human Body Model ESD Charged Device Model ESD Machine Model Rating −0.3 V to +6 V −0.3 V to +0.
PAGE 7
ADP1650 PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS BALL A1 INDICATOR 1 2 3 PGND SGND VIN SW GPIO2 GPIO1 VOUT STROBE EN A B VIN 1 GPIO2 2 GPIO1 3 LED_OUT SDA SDA 4 SCL SCL 5 D ADP1650 TOP VIEW 9 EN 8 SW 7 VOUT 6 LED_OUT NOTES 1. THE EXPOSED PADDLE MUST BE CONNECTED TO GROUND. 08837-004 TOP VIEW (BALL SIDE DOWN) Not to Scale 10 STROBE Figure 4. WLCSP Pin Configuration 08837-070 C Figure 5. LFCSP Pin Configuration Table 6.
PAGE 8
ADP1650 TYPICAL PERFORMANCE CHARACTERISTICS IL = inductor current, ILED = LED current, LED_OUT = LED output, IBAT = battery current. IL ILED 4 LED_OUT 3 SW 4 ILED 2 IL CH2 1A Ω CH4 500mA Ω 1 M100µs A CH1 T 402.2µs 400mV 08837-025 CH1 5V CH3 1V 08837-031 2 STROBE 1 CH1 2V CH2 100mA Ω CH4 25mA Ω M100ns A CH1 T 4.16007ms 1.6V Figure 9. Switching Waveforms, Flash Mode, ILED = 1500 mA Figure 6. Startup Flash Mode, VIN = 3.
PAGE 9
ADP1650 100 90 LED_OUT 80 EFFICIENCY (%) 70 IBAT 2 ILED 40 30 08837-036 20 1 CH2 2V CH4 1V CH2 1A Ω CH4 500mA Ω M40µs T 16% A CH1 0 0.3 680mV 100 –40°C +25°C +85°C +125°C 3.03 3.02 80 EFFICIENCY (%) 3.00 2.99 2.98 1.3 1.5 60 50 40 2.97 30 2.96 20 2.95 10 3.0 3.3 3.6 3.9 4.2 4.5 4.8 5.1 5.4 0 0.01 08837-038 0.1 1 OUTPUT CURRENT (A) Figure 16. Voltage Regulation Mode Efficiency vs. Load Current Figure 13. Switching Frequency vs.
PAGE 10
ADP1650 295 1111 293 CODE 1000 MIDPOINT (mV) 1010 1000 0110 0100 292 291 290 VIN = 3.6V 289 288 0010 50 75 100 125 150 Figure 18. ADC Die Temperature Mode Transfer Characteristic 10 60 110 TEMPERATURE (°C) Figure 21. ADC External Voltage Mode, Code 1000, Midpoint vs. Temperature 1111 1.0 1110 0.5 LED CURRENT ERROR (%) 1100 ADC RESULT (Binary) 286 –40 08837-063 25 08837-060 0 DIE TEMPERATURE (°C) 1010 1000 0110 0100 VIN = 3.2V VIN = 3.6V VIN = 4.2V 0 –0.5 –1.0 –1.5 –2.
PAGE 11
ADP1650 3.0 2.5 1.0 VIN = 3.2V VIN = 3.6V VIN = 4.2V 0.5 VIN = 3.2V VIN = 3.6V VIN = 4.2V LED CURRENT ERROR (%) 1.5 1.0 0.5 0 –0.5 0 –0.5 –1.0 –1.5 –1.0 –2.0 –40 10 60 TEMPERATURE (°C) 110 –2.5 –40 10 60 110 TEMPERATURE (°C) Figure 24. LED Current Error vs. Temperature, ILED = 1500 mA Figure 25. LED Current Error vs. Temperature, ILED = 1000 mA Rev. C | Page 11 of 32 08837-069 –2.0 –1.5 08837-068 LED CURRENT ERROR (%) 2.
PAGE 12
ADP1650 THEORY OF OPERATION The ADP1650 is a high power, I2C programmable white LED driver ideal for driving white LEDs for use as a camera flash. The ADP1650 includes a boost converter and a current regulator suitable for powering one high power white LED. MODES OF OPERATION WHITE LED DRIVER LED_MOD = [00] sets the device in standby mode, consuming 3 μA (typical).
PAGE 13
ADP1650 I(FLASH) ASSIST LIGHT The assist light provides continuous current programmable from 25 mA to 200 mA. Set the assist light current using the I_TOR bits (in Register 0x03). To enable assist, set LED_MOD to assist light mode and set OUTPUT_EN = 1 (in Register 0x04). Disable assist light mode by setting LED_MOD to standby mode or setting OUTPUT_EN = 0. LED CURRENT 0A FL_TIM STROBE I2C DATA BUS REG 0x02, FL_TIM = XXXX ms REG 0x03, I_FL = XXXXX mA I(ASSIST) LED CURRENT ADP1650 SETS OUTPUT_EN TO 0.
PAGE 14
ADP1650 TORCH-TO-FLASH MODE FREQUENCY FOLDBACK The driver can move directly from external torch mode (using GPIO1) to flash mode by bringing STROBE high before GPIO1 = torch is brought low. Bringing torch low before STROBE goes high prevents the flash from firing when STROBE goes high. Frequency foldback is an optional mode that optimizes efficiency by reducing the switching frequency to 1.5 MHz when VIN is slightly less than VOUT. Enable frequency foldback by setting FREQ_FB = 1 in Register 0x04.
PAGE 15
ADP1650 PROGRAMMABLE BATTERY DC CURRENT LIMIT ANALOG-TO-DIGITAL CONVERTER OPERATION The ADP1650 has four optional programmable input dc current limits that limit the maximum battery current that can be taken over all conditions. This allows higher LED currents to be used in a system with significant variation in LED forward voltage (VF) and supply battery voltage without risk of the current allocated to the flash being exceeded.
PAGE 16
ADP1650 Write ADC_EN = 10 to begin a die temperature measurement. The value can be read back from the ADC_VAL[5:2] bits 1 ms after the conversion has started. The most stable and accurate value of die temperature is available at the end of the flash pulse. initial peak as the junction temperature of the LED stabilizes. An LED temperature vs.
PAGE 17
ADP1650 10µF 1.0µH STROBE SW VIN VOUT = 5.0V ±8.5%, IMAX = 500mA VOUT GPIO2 SCL SDA, SCL I2C BUS POWER-ON RESET EN 0.1µF 10µF APPLICATIONS PROCESSOR ADP1650 VDD 47nF AUDIO IN+ SDA LED_OUT IN– 80kΩ AUDIO IN– SSM2315 160kΩ IN+ 80kΩ OUT+ MODULATOR FET (Σ-∆) DRIVER OUT– 47nF EN GPIO1 160kΩ SGND PGND SHUTDOWN SD BIAS INTERNAL OSCILLATOR POP/CLICK SUPPRESSION GND Figure 41. ADP1650 Voltage Regulation Mode: Class-D Audio Application Rev. C | Page 17 of 32 08837-019 3.2 TO 5.
PAGE 18
ADP1650 SAFETY FEATURES For critical fault conditions, such as output overvoltage, flash timeout, LED output short circuit, and overtemperature conditions, the ADP1650 has built-in protection modes. If a critical fault occurs, OUTPUT_EN (Register 0x04) is set to 0, and the driver shuts down. The appropriate fault bit is set in the fault information register (Register 0x05). The processor can read the fault information register through the I2C interface to determine the nature of the fault condition.
PAGE 19
ADP1650 I2C INTERFACE Figure 42 illustrates the I2C write sequence to a single register. The subaddress content selects which of the nine ADP1650 registers is written to. The ADP1650 sends an acknowledgment to the master after the 8-bit data byte has been written. Figure 43 shows the I2C read sequence of a single register. The ADP1650 includes an I2C-compatible serial interface for control of the LED current, as well as for readback of system status registers.
PAGE 20
ADP1650 I2C REGISTER MAP The lowest bit number (0) represents the least significant bit, and the highest bit number (7) represents the most significant bit. Table 9. Design Information Register (Register 0x00) Bit [7:0] R/W R Reset State 00100010 Table 10.
PAGE 21
ADP1650 Table 11.
PAGE 22
ADP1650 Table 12. Output Mode Register (Register 0x04) Bit Name IL_PEAK Bit [7:6] R/W R/W STR_LV 5 R/W FREQ_FB 4 R/W OUTPUT_EN 3 R/W STR_MODE 2 R/W LED_MOD [1:0] R/W Description Inductor peak current limit setting 00 = 1.75 A 01 = 2.25 A 10 = 2.75 A (default) 11 = 3.0 A 0 = edge sensitive 1 = level sensitive (default) 0 = frequency foldback to 1.5 MHz not allowed (default) 1 = frequency foldback to 1.
PAGE 23
ADP1650 Table 14.
PAGE 24
ADP1650 Table 15. Additional Mode Register, AD_MOD (Register 0x07) Bit Name DYN_OVP Bit 7 R/W R/W SW_LO 6 R/W STR_POL 5 R/W I_ILED [4:3] R/W IL_DC [2:1] R/W IL_DC_EN 0 R/W Description Dynamic OVP 0 = dynamic OVP off (default) 1 = dynamic OVP on Force 1.5 MHz switching frequency 0 = disabled (default) 1 = enabled Strobe polarity 0 = active low 1 = active high (default) Indicator LED current 00 = 2.75 mA (default) 01 = 5.5 mA 10 = 8.
PAGE 25
ADP1650 Table 17.
PAGE 26
ADP1650 APPLICATIONS INFORMATION capacitor, a low ESR capacitor is required. Table 19 provides a list of suggested input capacitors. EXTERNAL COMPONENT SELECTION Selecting the Inductor The ADP1650 boost converter increases the battery voltage to allow driving of one LED, whose voltage drop is higher than the battery voltage plus the current source headroom voltage. This allows the converter to regulate the LED current over the entire battery voltage range and with a wide variation of LED forward voltage.
PAGE 27
ADP1650 CEFF = COUT × (1 − TEMPCO) × (1 − TOL) where: CEFF is the effective capacitance at the operating voltage. TEMPCO is the worst-case capacitor temperature coefficient. TOL is the worst-case component tolerance. TEMPCO from −40°C to +85°C is 15%. TOL is 10%. COUT at VOUT (MAX) = 5 V, is 3 μF, as shown in Figure 44. 0 –10 –20 –30 –40 –50 –60 –70 –80 –90 0 1.26 2.52 3.78 5.04 DC BIAS VOLTAGE (V) 6.
PAGE 28
ADP1650 PCB LAYOUT Poor layout can affect performance, causing electromagnetic interference (EMI) and electromagnetic compatibility (EMC) problems, ground bounce, and power losses. Poor layout can also affect regulation and stability. Figure 45 shows optimized layouts implemented using the following guidelines: • • • • C1 Li-ION + L1 PGND Li-ION + C2 INDUCTOR DIGITAL INPUT/ OUTPUT AREA = 16.
PAGE 29
ADP1650 OUTLINE DIMENSIONS 0.660 0.602 0.544 1.54 1.50 1.46 0.022 REF SEATING PLANE 3 2 1 A BALL A1 IDENTIFIER 2.04 2.00 1.96 0.330 0.310 0.290 B 1.50 REF C D 0.380 0.352 0.324 0.04 MAX COPLANARITY BOTTOM VIEW (BALL SIDE UP) 1.00 REF 0.280 0.250 0.220 020409-B TOP VIEW (BALL SIDE DOWN) 0.50 REF Figure 47. 12-Ball Wafer Level Chip Scale Package [WLCSP] (CB-12-4) Dimensions shown in millimeters 2.48 2.38 2.23 3.10 3.00 SQ 2.90 0.50 BSC 6 1.74 1.64 1.49 EXPOSED PAD 0.50 0.40 0.
PAGE 30
ADP1650 NOTES Rev.
PAGE 31
ADP1650 NOTES Rev.