Document
AS3649
2500mA High Current LED Flash Driver
1 General Description
The AS3649 is an inductive high efficient DCDC step up converter with two current sources. The DCDC step up converter operates at a fixed frequency of 4MHz and includes soft startup to allow easy integration into noise sensitive RF systems. The two current sources can operate in flash / torch or video light modes.
The AS3649 includes flash timeout, overvoltage, overtemperature, undervoltage and LED short/open circuit protection functions. A TXMASK/TORCH function reduces the flash current in case of parallel operation to the RF power amplifier and avoids a system shutdown. Alternatively this pin can be used to directly operate the torch light directly. If the TXMask function is not used, it can be used as a hardware torch input (programmable).
A hardware NTC pin can be used to measure the LED temperature with the ADC and to automatically reduce the LED current if a temperature threshold is exceeded.
The AS3649 is controlled by an I2C interface and has a hardware reset pin ON. Setting ON=0 resets the AS3649. Interface input voltage levels are 1.8V compliant.
The AS3649 is available in a space-saving WL-CSP package measuring only 2.06x2.02x0.6mm and operates over the -30ºC to +85ºC temperature range.
Figure 1. Typical Operating Circuit
2 Key Features
High efficiency 4MHz fixed frequency DCDC Boost converter with soft start allows small coils - Stable even in coil current limit
LED current adjustable up to 2x1000mA(2x1250mA with current boost) or 2000mA and automatic load balancing for two LEDs
Automatic current adjustment for low battery voltage
PWM operation for lower output current for reliable light output of the LED; can run at 31.5kHz to avoid audible noise
Protection functions: Automatic Flash Timeout timer to protect the LED(s) Overvoltage and undervoltage Protection Overtemperature Protection LED short/open circuit protection
ADC to measure LED temperature
NTC to automatically reduce the flash current if the LED temperature is too high (programmable level)
I2C Interface with hardware reset pin
Available in tiny WL-CSP Package, 16 balls 0.5mm pitch, 2.06x2.02x0.6mm package size
3 Applications
Flash/Torch for mobile phones
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AS3649
Datasheet - Pin Assignments
4 Pin Assignments
Figure 2. Pin Assignments (Top View)
AS3649
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4.1 Pin Description
Table 1. Pin Description for AS3649
Pin Number1 A1 A2 A3
A4 B1 B2 B3
B4
C1 C2
Pin Name PGND2 PGND1
VIN
ON SW2 SW1 NTC
TXMASK/TORCH
VOUT2 VOUT1
Description
Power ground; make a short connection between all GND balls
Power ground; make a short connection between all GND balls
Positive supply voltage input - connect to supply and make a short connection to input capacitor CVIN and to coil LDCDC Hardware reset input; an active low signal resets the registers of AS3649 and enters shutdown (and I2C lines SDA and SCL are in high-Z), active high allows to operate the device
DCDC converter switching node - make a short connection to SW1 / coil LDCDC
DCDC converter switching node - make a short connection to SW2 / coil LDCDC
LED temperature sensor input (NTC) for LED overtemperature protection
Function 1: Connect to RF power amplifier enable signal - reduces currents during flash to avoid a system shutdown due to parallel operation of the RF PA and the flash driver Function 2: Operate torch current level without using the I2C interface to operate the torch without need to start a camera processor (if the I2C is connected to the camera processor
DCDC converter output capacitor - make a short connection to CVOUT / VOUT1
DCDC converter output capacitor - make a short connection to CVOUT / VOUT2
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AS3649
Datasheet - Pin Assignments
Table 1. Pin Description for AS3649
Pin Number1
Pin Name
C3 SCL
C4 SDA
D1 LED_OUT2 D2 LED_OUT1 D3 AGND D4 STROBE
Description
serial clock input for I2C interface serial data input/output for I2C interface (needs external pullup resistor) Flash LED current source Flash LED current source Analog ground; make a short connection between all GND balls Digital input with pulldown to control strobe time for flash function
1. Final pinout subject to change - now only used to count number of pins
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AS3649
Datasheet - Absolute Maximum Ratings
5 Absolute Maximum Ratings
Stresses beyond those listed in Table 2 may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in Electrical Characteristics on .