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PDF AS3643 Data sheet ( Hoja de datos )
| Número de pieza | AS3643 | |
| Descripción | 1300mA High Current LED Flash Driver | |
| Fabricantes | austriamicrosystems | |
| Logotipo |  |
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Datasheet
AS3643
1300mA High Current LED Flash Driver
1 General Description
The AS3643 is an inductive high efficient DCDC step up
converter with two current sinks. 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 sinks can oper-
ate in flash / torch / assist (=video) light modes.
The AS3643 includes flash timeout, overvoltage, over-
temperature, undervoltage and LED short circuit protec-
tion functions. A TXMASK/TORCH function reduces the
flash current in case of parallel operation to the RF
power amplifier and avoids a system shutdown. Alterna-
tively this pin can be used to directly operate the torch
light directly.
The AS3643 is controlled by an I2C interface and has a
hardware automatic shutdown if SCL=0 for 100ms.
Therefore no additional enable input is required for shut-
ting down of the device once the system shuts down.
The AS3643 is available in a space-saving WL-CSP
package measuring only 2.25x1.5x0.6mm 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 1300mA
Automatic current adjustment for low battery voltage
PWM operation for lower output current for reliable
light output of the LED; running at 31.25kHz 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
I2C Interface with automatic shutdown
5V constant voltage mode operation
Available in tiny WL-CSP Package, 13 balls 0.5mm
pitch 2.25x1.5x0.6mm, package size
3 Applications
Flash/torch/videolight for smartphones, feature-phones,
tablets, DSCs, DVCs
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www.austriamicrosystems.com/AS3643
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1.5-4
1 - 33
1 page  
AS3643
Datasheet, Confidential - Electrical Characteristics
Table 4. Electrical Characteristics (Continued)
Symbol
Parameter
Condition
Min Typ Max
VVOUTMAX
VVOUT overvoltage
protection
DCDC Converter Overvoltage Protection
5.0 5.3 5.6
ILIMIT
Current Limit for coil
LDCDC (Pin SW)
measured at 40%
PWM duty cycle3
maximum 40000s
lifetime operation in
overcurrent limit
default value
coil_peak=00b
1.0
coil_peak=01b
1.5
coil_peak=10b 1.8 2.0 2.23
coil_peak=11b
2.5
VLEDSHORT
Flash LED short
circuit detection
voltage
Voltage measured between pins VOUT1,2 and
LED_OUT1,2
1.0
TOVTEMP
TOVTEMPHY
ST
Overtemperature
Protection
Overtemperature
Hysteresis
Junction temperature
144
5
tFLASHTIMEO
UT
Flash Timeout Timer
Can be adjusted with register
flash_timeout (page 24)
accuracy
2 1280
-7.5 +7.5
VUVLO Undervoltage Lockout
Digital Interface
Falling VVIN
Rising VVIN
2.25 2.4 2.5
VUVLO VUVLO VUVLO
+0.05 +0.1 +0.15
VIH
High Level Input
Voltage
Pins SCL, SDA.
1.26
Pin TXMASK/TORCH in external torch mode
VIL
Low Level Input
Voltage
(ext_torch_on=10)
0.0
VVIN
0.54
VIHFLASH
VILFLASH
High Level Input
Voltage
Low Level Input
Voltage
Pin STROBE.
Pin TXMASK/TORCH for TxMask mode
(ext_torch_on=01)4
0.7
0.0
VVIN
0.54
VOL
Low Level Output
Voltage
pin SDA, IOL=3mA
0.3
ILEAK
Leakage current
Pins SCL, SDA
-1.0 0.0 +1.0
IPD
Pulldown current to
GND5
Pins TORCH, STROBE and TXMASK/TORCH
36
tDEBTORCH
TORCH debounce
time
6.3 9 11.7
tTIMEOUT
SCL timeout
In indicator, assist or flash mode, if SCL is low
longer than this timeout, the AS3643
automatically enters shutdown mode
35
100
I2C mode timings - see Figure 3 on page 7
fSCLK SCL Clock Frequency
1/
tTIMEO
UT
400
Bus Free Time
tBUF Between a STOP and
START Condition
1.3
tHD:STA
Hold Time (Repeated)
START Condition6
0.6
Unit
V
A
V
ºC
ºC
ms
%
V
V
V
V
V
V
V
µA
µA
ms
ms
kHz
µs
µs
www.austriamicrosystems.com/AS3643
1.5-4
5 - 33
5 Page 
AS3643
Datasheet, Confidential - Detailed Description
4MHz/1MHz Operating Mode Switching
If freq_switch_on (see page 26)=1 and in flash and assist light mode (indicator mode or low current mode using PWM
mode -see mode_setting (page 24) - always will use pulseskip) if led_current>=40h , the DCDC converter always oper-
ates in PWM mode (exception: PFM mode is allowed during startup) to reduce EMI in EMI sensitive systems. For flash
and assist light mode and high duty cycles close to 100% on-time (maximum duty cycle) of the PMOS, the DCDC con-
verter can switch into a 1MHz operating mode and maximum duty cycle to improve efficiency for this load condition3.
The DCDC converter returns back to its normal 4MHz operating frequency when load or supply conditions change.
Due to this switching between two fixed frequencies the noise spectrum of the system is exactly defined and predict-
able. If improved efficiency is required, the fixed switching between 1MHz / 4MHz can be disabled by freq_switch_on
(see page 26)=0. In this case pulseskip will be used.
The internal circuit for switching between these two frequencies is shown in Figure 17:
Figure 17. Internal circuit of 4MHz/1Mhz selection
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Note: For simplicity Figure 17 shows only a single current sink.
Protection and Fault Detection Functions
The protection functions protect the AS3643 and the LED(s) against physical damage. In most cases a Fault register
bit is set, which can be readout by the I2C interface. The fault bits are automatically cleared by a I2C readout of the fault
register. Additionally the DCDC is stopped and the current sinks are disabled4 by resetting out_on=0,
mode_setting=00 and ext_torch_on=00.
Overvoltage Protection
In case of no or a broken LED(s) at the pin LED_OUT1/2 and an enabled DCDC converter, the voltage on VOUT1/2
rises until it reaches VVOUTMAX (overvoltage condition) and the voltage across the current source is below low_vds5.,
the DCDC converter is stopped, the current sources are disabled and the bit fault_ovp (see page 25) is set6.
3. Efficiency compared to a 4MHz only DCDC converter forced to operate with minimum duty cycle.
4. Applies for all faults except TXMASK event occurred
5. If overvoltage is reached, but none of the low_vds comparator(s) triggers, VOUT1/2 is still regulated below
VVOUTMAX.
6. In constant voltage mode (5V generation, register bit const_v_mode=1) this fault is disabled.
www.austriamicrosystems.com/AS3643
1.5-4
11 - 33
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