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 I C 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.
2
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)
I
2
C 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
Figure 1. Typical Operating Circuit
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AS3649
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AS3649
Datasheet - P i n A s s i g n m e n t s
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 Number
A1
A2
A3
A4
B1
B2
B3
1
Pin Name
PGND2
PGND1
VIN
ON
SW2
SW1
NTC
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
C
VIN
and to coil L
DCDC
Hardware reset input; an active low signal resets the registers of AS3649 and enters shutdown
(and I C 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 L
DCDC
DCDC converter switching node - make a short connection to SW2 / coil L
DCDC
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 I C interface to operate the torch
without need to start a camera processor (if the I C is connected to the camera processor
2
2
2
B4
TXMASK/TORCH
C1
C2
VOUT2
VOUT1
DCDC converter output capacitor - make a short connection to C
VOUT
/ VOUT1
DCDC converter output capacitor - make a short connection to C
VOUT
/ VOUT2
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AS3649
Datasheet - P i n A s s i g n m e n t s
Table 1. Pin Description for AS3649
Pin Number
C3
C4
D1
D2
D3
D4
1
Pin Name
SCL
SDA
LED_OUT2
LED_OUT1
AGND
STROBE
serial clock input for I C interface
2
Description
serial data input/output for I C 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
2
1. Final pinout subject to change - now only used to count number of pins
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AS3649
Datasheet - A b s o l u t e M a x i m u m R a t i n g s
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 page 5
is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect device reliability.
Table 2. Absolute Maximum Ratings
Parameter
VIN to GND
STROBE, TXMASK/TORCH, SCL, SDA, ON, NTC to
GND
SW1/2, VOUT1/2, LED_OUT1/2 to GND
VOUT1/2 to SW1/2
voltage between AGND, PGND1/2 pins
Input Pin Current without causing latchup
Continuous Power Dissipation (T
A
= +70ºC)
Continuous power dissipation
Continuous power dissipation derating factor
Electrostatic Discharge
ESD HBM
ESD CDM
Temperature Ranges and Storage Conditions
Junction to ambient thermal resistance
Junction Temperature
Storage Temperature Range
Humidity
Body Temperature during Soldering
Moisture Sensitivity Level (MSL)
MSL 1
-55
5
50
3
Min
-0.3
-0.3
-0.3
-0.3
0.0
-100
Max
+7.0
VIN + 0.3
+7.0
0.0
+100
+I
IN
Units
V
V
V
V
V
mA
Comments
max. +7V
Note:
Diode between VOUT1/2 and SW1/2
short connection required
Norm: EIA/JESD78
1470
20
±2000
±500
mW
mW/ºC
V
V
P
T
at 70ºC
P
DERATE
1
2
Norm: JEDEC JESD22-A114F
Norm: JEDEC JESD 22-C101E
For more information about thermal metrics, see
application note AN01 Thermal Characteristics
Internally limited (overtemperature protection),
max. 20000s
Non condensing
according to IPC/JEDEC J-STD-020
Represents a max. floor life time of unlimited
ºC/W
ºC
ºC
%
ºC
+150
+125
85
+260
1. Depending on actual PCB layout and PCB used measured on demoboard; for peak power dissipation during flashing see document
'AS3649 Thermal Measurements'
2. P
DERATE
derating factor changes the total continuous power dissipation (P
T
) if the ambient temperature is not 70ºC. Therefore for e.g.
T
AMB
=85ºC calculate P
T
at 85ºC = P
T
- P
DERATE
* (85ºC - 70ºC)
3. Measured on AS3649 demoboard.
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AS3649
Datasheet - E l e c t r i c a l C h a r a c t e r i s t i c s
6 Electrical Characteristics
V
VIN
= +2.7V to +4.4V, T
AMB
= -30ºC to +85ºC, unless otherwise specified. Typical values are at V
VIN
= +3.7V, T
AMB
= +25ºC, unless otherwise
specified.
Table 3. Electrical Characteristics
Symbol
V
VIN
V
VINREDUCED_
FUNC
Parameter
Supply Voltage
Supply Voltage
Shutdown Current
Standby Current
Operating Temperature
Condition
Pin VIN
AS3649 functionally working, but not all parameters
fulfilled
TXMASK/TORCH=L, STROBE=L, ON=L, V
VIN
<3.7V
Interface active, TXMASK/TORCH=L, STROBE=L
V
VIN
<3.7V
Min
2.7
2.5
4.4
Typ
3.7
Max
4.4
2.7
5.5
Unit
V
V
µA
µA
ºC
%
General Operating Conditions
I
SHUTDOWN
I
STANBY
T
AMB
1
1.0
1.0
-30
25
83
2.0
10
85
Application Efficiency
L
COIL
=0.6µH@3A, L
ESR
=60m, LED_OUT1,2=2000mA,
(DCDC and current source)
t
FLASH
<300ms, VF
LED
=3.7V
V
VIN
>3.3V, T
AMB
<85ºC, I
LED_OUT
<2000mA
If T
AMB
or I
LED_OUT
is reduced or V
VIN
is increased,
longer flash times are allowed.
For longer flash durations, see section
Current Reduction
by VIN Measurements in Flash Mode and Diagnostic
Pulse on page 15
t
FLASH
Flash Duration
300
ms
DCDC Step Up Converter
V
VOUT
R
PMOS
R
NMOS
f
CLK
V
VOUT5V
DCDC Boost output
Voltage
(pin VOUT1/2)
On-resistance
On-resistance
Operating Frequency
DCDC Boost output
Voltage
(pin VOUT1/2)
DCDC internal PMOS switch
DCDC internal NMOS switch
All internal timings are derived from this oscillator
Constant voltage mode operation
const_v_mode (see
page 30)=1
-7.5%
2.8
45
47
4.0
5.0
+7.5%
5.5
V
m
m
MHz
V
Current Sources
V
LED
LED forward voltage
Two flash LEDs, I
LED_OUT
<2x1000mA
Single flash LED, I
LED_OUT
<1800mA
V
VIN
>3.3V,
coil_peak=11b,
L
COIL
=0.6µH@3.4A, L
ESR
=60m
coil SPM3012T-1R0M,
t
FLASH
<300ms
dual flash LED,
current_boost=0
single flash LED
2.8
2.8
0
0
0
-7
-5
730
530
500
40
3.32
3.32
4.0
4.4
2000
2000
2500
+7
+5
2
V
V
mA
mA
mA
%
%
µs
µs
µs
mA
PP
I
LED_OUT
LED_OUT1/2 current
combined
LED_OUT1/2 current
combined
LED_OUT1/2 current
source accuracy
I
LED_OUT_BO
OST
Dual flash LED,
current_boost=1
Otherwise
I
LED_OUT
=500mA...800mA, 0ºC<T
J
<100ºC
Rampup initiated by I C command
2
I
LED_OUT
I
LED_OUT
RAMP
LED_OUT1/2 ramp time
Rampup started by STROBE
Full range Ramp-down
I
LED_OUT
RIPPLE
LED_OUT current ripple
I
LED_OUT
= 1000mA
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