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PDF AS3644 Data sheet ( Hoja de datos )
| Número de pieza | AS3644 | |
| Descripción | Ultra Small Low Cost 320mA Inductive | |
| Fabricantes | austriamicrosystems | |
| Logotipo |  |
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Datasheet
AS3644
Ultra Small Low Cost 320mA Inductive White LED Flash Driver
1 General Description
The AS3644 is an inductive high efficient DCDC step up
converter driving a current source. 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 current source operates in
flash/torch/assist (video/autofocus) mode.
The AS3644 includes flash timer, overvoltage, overtem-
perature, undervoltage and LED short circuit protection
functions.
The AS3644 is able to detect a broken coil. Together
with the LED short and open detection the AS3644 can
be used to verify the connection to its external compo-
nents and allowing in-circuit test. This reduces test time
and simplifies production test procedures.
The AS3644 is controlled by an I2C interface to allow
sophisticated control of all settings like currents and tim-
ings.
The complete flash driver solution measures only
11mm2 PCB area.
The AS3644 is available in a space-saving WL-CSP
package measuring only 1.5x1.1x0.6mm and operates
over the -30ºC to +85ºC temperature range.
Figure 1. Typical Operating Circuit
2 Key Features
Total flash driver solution only 11mm2
High efficiency 4MHz fixed frequency DCDC Boost
converter with soft start allows small coils
LED currents
260mA to 320mA flash current (20mA steps)
51.6mA or 72.3mA Assist light (=torch) current
Flash LED(s) cathode connected to ground:
Improved thermal performance (ground = heat sink)
Simplified PCB layout
Adjustable Flash Timer
30ms to 480ms in 30ms steps
Flash, Torch, Assist and Indicator Mode
Protection functions:
Automatic Flash timer to protect the LED
Overvoltage and undervoltage Protection
Overtemperature Protection
LED short circuit protection
Available in tiny WL-CSP Packages
2x3 balls 0.5mm pitch, 1.5x1.1x0.6mm package size
3 Applications
Flash/Torch for mobile phones, digital cameras and PDA
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www.austriamicrosystems.com/AS3644
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1.2.2
1 - 23
1 page  
AS3644
Datasheet - Electrical Characteristics
Table 3. Electrical Characteristics (Continued)
Symbol
Parameter
Condition
Min Typ Max Unit
TOVTEMP
TOVTEMPHY
ST
Overtemperature
Protection
Overtemperature
Hysteresis
Junction temperature
144 ºC
5 ºC
tFLASHTIMER
Flash Timer
Can be adjusted by register flash_timer (see
page 16)
-7.5%
30 to
480
+7.5%
ms
VUVLO
Undervoltage
Lockout3
Digital Interface
Falling VVIN
Rising VVIN
2.3 2.4 2.5
VUVLO VUVLO VUVLO
+0.05 +0.1 +0.15
V
V
VIH
High Level Input
Voltage
VIL
Low Level Input
Voltage
Pins SCL, SDA4
1.26
0.0
VVIN-
0.2
0.54
V
V
VOL
Low Level Output Pin SDA with pullup >1k to digital supply <2V,
Voltage
VVIN>2.7V
I2C interface timings - see Figure 3 on page 6
0.3 V
tWAKEUP
Wakeup Time
Minimum time from SDA or SCL going high to
first I2C start command
500
µs
tTIMEOUT
I2C timeout time
In flash, assist light and indicator mode if SCL
and SDA are L for tTIMEOUT, the AS3644 enters
automatically shutdown mode
35
ms
fSCLK SCL Clock Frequency
1/
tTIMEO
UT
400 kHz
Bus Free Time
tBUF Between a STOP and
START Condition
1.3 µs
tHD:STA
Hold Time (Repeated)
START Condition5
0.6 µs
tLOW
LOW Period of SCL
Clock
1.3 µs
tHIGH
HIGH Period of SCL
Clock
0.6 µs
tSU:STA
Setup Time for a
Repeated START
Condition
0.6 µs
tHD:DAT
Data Hold Time6
0 0.9 µs
tSU:DAT
Data Setup Time7
100 ns
tR
tF
tSU:STO
Rise Time of Both
SDA and SCL Signals
Fall Time of Both SDA
and SCL Signals
Setup Time for STOP
Condition
20 +
0.1CB
20 +
0.1CB
0.6
300 ns
300 ns
µs
CB
Capacitive Load for
Each Bus Line
CB — total capacitance of one bus line in pF
400 pF
www.austriamicrosystems.com/AS3644
1.2.2
5 - 23
5 Page 
AS3644
Datasheet - Detailed Description
DCDC Overvoltage Protection
In case of no or a broken LED at the pin LED_OUT and an enabled DCDC converter, the voltage on VOUT rises until
it reaches VVOUTMAX (overvoltage condition) and the voltage across the current source does not reach regulation
(VOUT-VLED < VILED_COMP). If this condition is detected, the DCDC converter is stopped, the current sources are dis-
abled and the bit fault_ovp (see page 17) is set.
DCDC Broken Coil Detection
If the coil LDCDC is broken, the AS3644 is not powered by the pin SW connected to VOUT by the internal switch. Due
to the protection diodes between SCL to VOUT and SDA to VOUT, the AS3644 can be powered through these diodes.
The AS3644 detects this error condition by comparing the voltage on SCL and VOUT. If the voltage on VOUT is lower
compared to the voltage on SCL, the AS3644 will ignore any I2C write commands. Therefore the application can simply
detect this condition.
Note: Due to the broken coil detection, the high levels of SDA and SCL should be always below the supply voltage.
LED Short Circuit Protection
After the startup of the DCDC converter, the voltage on LED_OUT is continuously monitored and compared against
VLEDSHORT. If the voltage stays below VLEDSHORT, the DCDC is stopped (as a shorted LED is assumed), the current
sources are disabled and the bit fault_led_short (see page 17) is set.
Overtemperature Protection
The junction temperature of the AS3644 is continuously monitored. If the temperature exceeds TOVTEMP, the DCDC is
stopped, the current sources are disabled and the bit fault_overtemp (see page 17) is set. The driver cannot be re-
enabled unless the junction temperature drops below TOVTEMP-TOVTEMPHYST.
Flash Timer
The duration of the flash is defined by the register flash_timer (see page 16). After the timer expires, the DCDC is
stopped and the flash current source (on pin LED_OUT) is disabled.
Supply undervoltage Protection
If the voltage on the pin VOUT (=battery voltage) is or falls below VUVLO, the AS3644 is kept in shutdown state and in
all registers are set to their default state.
Note: During operation of the DCDC converter, the supply undervoltage protection will still monitor the DCDC output
voltage only. Therefore the supply undervoltage protection will only monitor the battery voltage if the DCDC
converter is switched off and the output capacitor is discharged down to the supply voltage.
Wakeup Circuit - Power off detection
In flash, assist light and indicator mode, if SCL and SDA are L for more than tTIMEOUT, shutdown mode is automatically
entered. This feature automatically detects a power-off of the controlling circuit driving SCL and SDA.
I2C Serial Data Bus
The AS3644 supports the I2C bus protocol. A device that sends data onto the bus is defined as a transmitter and a
device receiving data as a receiver. The device that controls the message is called a master. The devices that are
controlled by the master are referred to as slaves. A master device that generates the serial clock (SCL), controls the
bus access, and generates the START and STOP conditions must control the bus. The AS3644 operates as a slave on
the I2C bus. Within the bus specifications a standard mode (100kHz maximum clock rate) and a fast mode (400kHz
maximum clock rate) are defined. The AS3644 works in both modes. Connections to the bus are made through the
open-drain I/O lines SDA and SCL.
The following bus protocol has been defined (Figure 19):
Data transfer may be initiated only when the bus is not busy.
During data transfer, the data line must remain stable whenever the clock line is HIGH. Changes in the data line
while the clock line is HIGH are interpreted as control signals.
Accordingly, the following bus conditions have been defined:
www.austriamicrosystems.com/AS3644
1.2.2
11 - 23
11 Page | ||
| Páginas | Total 23 Páginas | |
| PDF Descargar | [ Datasheet AS3644.PDF ] | |
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