AS3649
2500mA High Current LED Flash Driver
www.ams.com/AS3649 1.0-2 1 - 39
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
AS3649
AS3649
Datasheet - Pin Assignments
www.ams.com/AS3649 1.0-2 2 - 39
4 Pin Assignments
Figure 2. Pin Assignments (Top View)
4.1 Pin Description
Table 1. Pin Description for AS3649
Pin Number1Pin Name Description
A1 PGND2 Power ground; make a short connection between all GND balls
A2 PGND1 Power ground; make a short connection between all GND balls
A3 VIN Positive supply voltage input - connect to supply and make a short connection to input capacitor
CVIN and to coil LDCDC
A4 ON 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
B1 SW2 DCDC converter switching node - make a short connection to SW1 / coil LDCDC
B2 SW1 DCDC converter switching node - make a short connection to SW2 / coil LDCDC
B3 NTC LED temperature sensor input (NTC) for LED overtemperature protection
B4 TXMASK/TORCH
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
C1 VOUT2 DCDC converter output capacitor - make a short connection to CVOUT / VOUT1
C2 VOUT1 DCDC converter output capacitor - make a short connection to CVOUT / VOUT2
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AS3649
AS3649
Datasheet - Pin Assignments
www.ams.com/AS3649 1.0-2 3 - 39
C3 SCL serial clock input for I2C interface
C4 SDA serial data input/output for I2C interface (needs external pullup resistor)
D1 LED_OUT2 Flash LED current source
D2 LED_OUT1 Flash LED current source
D3 AGND Analog ground; make a short connection between all GND balls
D4 STROBE 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
Table 1. Pin Description for AS3649
Pin Number1Pin Name Description
AS3649
Datasheet - Absolute Maximum Ratings
www.ams.com/AS3649 1.0-2 4 - 39
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 Min Max Units Comments
VIN to GND -0.3 +7.0 V
STROBE, TXMASK/TORCH, SCL, SDA, ON, NTC to
GND -0.3 VIN + 0.3 V max. +7V
SW1/2, VOUT1/2, LED_OUT1/2 to GND -0.3 +7.0 V
VOUT1/2 to SW1/2 -0.3 V Note: Diode between VOUT1/2 and SW1/2
voltage between AGND, PGND1/2 pins 0.0 0.0 V short connection required
Input Pin Current without causing latchup -100 +100
+IIN mA Norm: EIA/JESD78
Continuous Power Dissipation (TA = +70ºC)
Continuous power dissipation 1470 mW PT at 70ºC1
1. Depending on actual PCB layout and PCB used measured on demoboard; for peak power dissipation during flashing see document
'AS3649 Thermal Measurements'
Continuous power dissipation derating factor 20 mW/ºC PDERATE2
2. PDERATE derating factor changes the total continuous power dissipation (PT) if the ambient temperature is not 70ºC. Therefore for e.g.
TAMB=85ºC calculate PT at 85ºC = PT - PDERATE * (85ºC - 70ºC)
Electrostatic Discharge
ESD HBM ±2000 V Norm: JEDEC JESD22-A114F
ESD CDM ±500 V Norm: JEDEC JESD 22-C101E
Temperature Ranges and Storage Conditions
Junction to ambient thermal resistance 503
3. Measured on AS3649 demoboard.
ºC/W For more information about thermal metrics, see
application note AN01 Thermal Characteristics
Junction Temperature +150 ºC Internally limited (overtemperature protection),
max. 20000s
Storage Temperature Range -55 +125 ºC
Humidity 5 85 % Non condensing
Body Temperature during Soldering +260 ºC according to IPC/JEDEC J-STD-020
Moisture Sensitivity Level (MSL) MSL 1 Represents a max. floor life time of unlimited
AS3649
Datasheet - Electrical Characteristics
www.ams.com/AS3649 1.0-2 5 - 39
6 Electrical Characteristics
VVIN = +2.7V to +4.4V, TAMB = -30ºC to +85ºC, unless otherwise specified. Typical values are at VVIN = +3.7V, TAMB = +25ºC, unless otherwise
specified.
Table 3. Electrical Characteristics
Symbol Parameter Condition Min Typ Max Unit
General Operating Conditions
VVIN Supply Voltage Pin VIN 2.7 3.7 4.4 V
VVINREDUCED_
FUNC Supply Voltage AS3649 functionally working, but not all parameters
fulfilled
2.5 2.7 V
4.4 5.5
ISHUTDOWN Shutdown Current TXMASK/TORCH=L, STROBE=L, ON=L, VVIN<3.7V 1.0 2.0 µA
ISTANBY Standby Current Interface active, TXMASK/TORCH=L, STROBE=L
VVIN<3.7V 1.0 10 µA
TAMB Operating Temperature -30 25 85 ºC
1Application Efficiency
(DCDC and current source)
LCOIL=0.6µH@3A, LESR=60m, LED_OUT1,2=2000mA,
tFLASH<300ms, VFLED=3.7V 83 %
tFLASH Flash Duration
VVIN>3.3V, TAMB<85ºC, ILED_OUT<2000mA
If TAMB or ILED_OUT is reduced or VVIN 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
300 ms
DCDC Step Up Converter
VVOUT
DCDC Boost output
Voltage
(pin VOUT1/2)
2.8 5.5 V
RPMOS On-resistance DCDC internal PMOS switch 45 m
RNMOS On-resistance DCDC internal NMOS switch 47 m
fCLK Operating Frequency All internal timings are derived from this oscillator -7.5% 4.0 +7.5% MHz
VVOUT5V
DCDC Boost output
Voltage
(pin VOUT1/2)
Constant voltage mode operation const_v_mode (see
page 30)=1 5.0 V
Current Sources
VLED LED forward voltage Two flash LEDs, ILED_OUT<2x1000mA 2.8 3.32 4.0 V
Single flash LED, ILED_OUT<1800mA 2.8 3.32 4.4 V
ILED_OUT LED_OUT1/2 current
combined
VVIN>3.3V, coil_peak=11b,
LCOIL=0.6µH@3.4A, LESR=60m
coil SPM3012T-1R0M,
tFLASH<300ms
dual flash LED,
current_boost=0 0 2000 mA
single flash LED 0 2000 mA
ILED_OUT_BO
OST
LED_OUT1/2 current
combined Dual flash LED, current_boost=1 0 25002mA
ILED_OUTLED_OUT1/2 current
source accuracy
Otherwise -7 +7 %
ILED_OUT=500mA...800mA, 0ºC<TJ<100ºC -5 +5 %
ILED_OUT
RAMP LED_OUT1/2 ramp time
Rampup initiated by I2C command 730 µs
Rampup started by STROBE 530 µs
Full range Ramp-down 500 µs
ILED_OUT
RIPPLE LED_OUT current ripple ILED_OUT = 1000mA 40 mAPP
AS3649
Datasheet - Electrical Characteristics
www.ams.com/AS3649 1.0-2 6 - 39
VILED_COMP LED_OUT current source
voltage compliance
Minimum voltage between pin VOUT1/2 and LED_OUT1/
2 for operation of the current source with current_boost=0 230 mV
VILED_COMP
_BOOST VILED_COMP with current_boost=1 290 mV
LLED_CONNECT
ION LED connection inductance Represents a maximum connection length of 10cm (LED
connection and ground return path) 100 nH
Protection and Fault Detection Functions (see page 12)
VVOUTMAX VVOUT overvoltage
protection DCDC Converter Overvoltage Protection 5.0 5.3 5.6 V
ILIMIT
Current Limit for coil
LDCDC (Pin SW)
measured at 25% PWM
duty cycle3
maximum 40000s lifetime
operation in overcurrent
limit
coil_peak=00b 2.25 2.5 2.75
A
coil_peak=01b 2.61 2.9 3.19
Default value coil_peak (see page
23)=10b 3.0 3.3 3.63
coil_peak=11b 3.3 3.7 4.1
VLEDSHORT Flash LED short circuit
detection voltage Voltage measured between pins LED_OUT1,2 and GND 1.2 V
TOVTEMP Overtemperature
Protection Junction temperature
144 ºC
TOVTEMPHYS
T
Overtemperature
Hysteresis 5ºC
tFLASHTIMEO
UT Flash Timeout Timer Can be adjusted with register flash_timeout (page 26) 4 1124 ms
Accuracy -7.5 +7.5 %
VUVLO Undervoltage Lockout
Falling VVIN 2.25 2.4 2.5 V
Rising VVIN VUVLO
+0.05
VUVLO
+0.1
VUVLO
+0.15 V
VIN_LOW_VOLTA
GE
Battery Low Voltage
Protection
Defined by vin_low_v - see Current Reduction by VIN
Measurements in Flash Mode and Diagnostic Pulse on
page 15
-2.5% 3.0-
3.47 +2.5% V
Protection and Fault Detection Functions - NTC
INTC NTC Current Source Adjustable by ntc_current (page
25) in 40µA steps
Range 40 600 µA
I - accuracy
V(NTC) <= 1.7V
-7 +7 %4
-5 +5 µA
VNTC_TH Threshold for
overtemperature
If ntc_on (page 25)=1 and the voltage on NTC drops
below VNTC_TH, any flash/torch or pwm operation of
LED_OUT is stopped
1.0 V
ADC
Resolution 10 bits
Range
ADC input range; channel
selected by
adc_channel (page 27)
ADC Code 0 full
scale
NTC 0.0 2.2 V
VIN 0.0 5.5 V
TJUNC (AS3649 junction temperature) see Tab le 6 ºC
Accuracy ADC measurement
accuracy
NTC -1.5 +1.5 % full
scale
TJUNC (-30ºC...150ºC) -8 +8 ºC
TJUNC (0ºC...85ºC) -5 +5
Table 3. Electrical Characteristics (Continued)
Symbol Parameter Condition Min Typ Max Unit
AS3649
Datasheet - Electrical Characteristics
www.ams.com/AS3649 1.0-2 7 - 39
Digital Interface
VIH High Level Input Voltage Pins ON, SCL, SDA.
and TXMASK/TORCH
1.26 VVIN V
VIL Low Level Input Voltage 0.0 0.54 V
VIHFLASH High Level Input Voltage Pin STROBE. 0.84 VVIN V
VILFLASH Low Level Input Voltage 0.0 0.54 V
VOL Low Level Output Voltage Pin SDA, IOL=3mA 0.3 V
ILEAK Leakage current Pins ON, SCL, SDA -1.0 0.0 +1.0 µA
IPD Pulldown current to GND5Pins STROBE and TXMASK/TORCH 36 µA
tDEBTORCH TORCH debounce time 6.3 9 11.7 ms
tDEBTXMASK TXMASK debounce timer 1.5 µs
I2C mode timings - see Figure 3 on page 8
fSCLK SCL Clock Frequency 0 400 kHz
tBUF
Bus Free Time Between a
STOP and START
Condition
1.3 µs
tHD:STA Hold Time (Repeated)
START Condition60.6 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 Time700.9µs
tSU:DAT Data Setup Time8100 ns
tRRise Time of Both SDA and
SCL Signals
20 +
0.1CB300 ns
tFFall Time of Both SDA and
SCL Signals
20 +
0.1CB300 ns
tSU:STO Setup Time for STOP
Condition 0.6 µs
CBCapacitive Load for Each
Bus Line CB — total capacitance of one bus line in pF 400 pF
CI/O I/O Capacitance (SDA,
SCL) 10 pF
1. To improve efficiency at low output currents, the active part of the internal switching transistor PMOS is reduced in size to 1/5 its original
size. This reduces the current required to drive the PMOS transistor and therefore improves overall efficiency at low output currents.
2. The maximum current driving capability depends on supply voltage VVIN, LED forward voltage and coil peak current limit.
3. Due to slope compensation of the current limit, ILIMIT changes with duty cycle - see Figure 16 on page 11.
4. Accuracy defined in % of current setting and in absolute value (µA), accuracy values have to be added together
5. A pulldown current of 36µA is equal to a pulldown resistor of 42k at 1.5V
6. After this period, the first clock pulse is generated
7. A device must internally provide a hold time of at least 300ns for the SDA signal (referred to the VIHMIN of the SCL signal) to bridge the
undefined region of the falling edge of SCL.
8. A fast-mode device can be used in a standard-mode system, but the requirement tSU:DAT = to 250ns must then be met. This is
automatically the case if the device does not stretch the LOW period of the SCL signal. If such a device does stretch the LOW period of
the SCL signal, it must output the next data bit to the SDA line tR max + tSU:DAT = 1000 + 250 = 1250ns before the SCL line is released.
Table 3. Electrical Characteristics (Continued)
Symbol Parameter Condition Min Typ Max Unit
AS3649
Datasheet - Electrical Characteristics
www.ams.com/AS3649 1.0-2 8 - 39
6.1 Timing Diagrams
Figure 3. I2C mode Timing Diagram
SCL
SDA
tBUF
tHD:STA
tSU:STA
REPEATED
START
tSU:STO
tF
tSU:DAT
tHIGH
tHD:DAT
tR
tLOW
tHD:STA
STARTSTOP
www.ams.com/AS3649 1.0-2 9 - 39
AS3649
Datasheet - Typical Operating Characteristics
7 Typical Operating Characteristics
VVIN = 3.7V, TA = +25ºC (unless otherwise specified)
Figure 4. DCDC Efficiency vs. VVIN Figure 5. Application Efficiency (PLED/PVIN) vs. VVIN
60
65
70
75
80
85
90
95
100
2.83.03.23.43.63.84.04.24.4
Efficiency %
Input Voltage (V)
ILED = 2500mA, VFLED=3.55V (2 LEDs)
ILED = 2000mA, VFLED=3.45V (2 LEDs)
ILED = 1600mA, VFLED=3.7V (1 LED)
ILED = 1600mA / dcdc_skip_enable=0
ILED = 1000mA, VFLED=3.45V (1 LED)
60
65
70
75
80
85
90
2.83.03.23.43.63.84.04.24.4
Efficiency %
Input Voltage (V)
ILED = 2500mA, VFLED=3.55V (2 LEDs)
ILED = 2000mA, VFLED=3.45V (2 LEDs)
ILED = 1600mA, VFLED=3.7V (1 LED)
ILED = 1600mA / dcdc_skip_enable=0
ILED = 1000mA, VFLED=3.45V (1 LED)
Figure 6. Battery Current vs. VVIN Figure 7. Efficiency at low currents (298mA/100mA)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
2.83.03.23.43.63.84.04.24.4
Battery Current [A]
Input Voltage (V)
ILED = 2500mA, VFLED=3.55V (2 LEDs)
ILED = 2000mA, VFLED=3.45V (2 LEDs)
ILED = 1600mA, VFLED=3.7V (1 LED)
ILED = 1600mA / dcdc_skip_enable=0
ILED = 1000mA, VFLED=3.45V (1 LED)
limited by 3.7A
peak current setting
50
55
60
65
70
75
80
85
90
2.83.03.23.43.63.84.04.24.4
Efficiency %
Input Voltage (V)
ILED = 298mA/1LED DCDC Efficiency
ILED = 298mA/1LED Application Efficiency
ILED = 100mA x 2 LEDs DCDC Efficiency
ILED = 100mA x 2 LEDs Application Efficiency
Figure 8. ILED Startup (ILED_OUT=1.0A) Figure 9. IVIN, ILED Startup (ILED_OUT=800mA)
www.ams.com/AS3649 1.0-2 10 - 39
AS3649
Datasheet - Typical Operating Characteristics
Figure 10. ILED vs. VVIN Figure 11. VOUT / ILED_OUT ripple, ILED_OUT = 2x1.0A
0.0
0.5
1.0
1.5
2.0
2.5
3.0
2.83.03.23.43.63.84.04.24.4
LED Current [A]
Input Voltage (V)
ILED = 2500mA, VFLED=3.55V (2 LEDs)
ILED = 2000mA, VFLED=3.45V (2 LEDs)
ILED = 1600mA, VFLED=3.7V (1 LED)
ILED = 1000mA, VFLED=3.45V (1 LED)
limited by 3.7A
peak current setting
Figure 12. Diagnostic Pulse Operation Figure 13. TxMask operation waveform (ILED, IVIN)
VVIN=3.62V
vin_low_v=3.47V
Figure 14. Timeout Timer Figure 15. NTC operation (overtemperature triggered)
AS3649
Datasheet - Detailed Description
www.ams.com/AS3649 1.0-2 11 - 39
8 Detailed Description
The AS3649 is a high performance DCDC step up converter with internal PMOS and NMOS switches. Its output is connected to one or two flash
LEDs1 with two internal current sources and hardware LED temperature protection using an external NTC. The device is controlled by the pins
SDA and SCL in I2C mode and includes a hardware reset input ON.
The actual operating mode like standby, torch light, indicator or flash mode, can then be chosen by the interface. If not in standby mode, the
device automatically enters shutdown and resets all registers by setting pin ON=0.
The AS3649 includes a fixed frequency DCDC step-up with accurate startup control. Together with the current source (on LED_OUT1/2) it
includes several protection and safety functions.
8.1 Internal Circuit Diagram
Figure 16. Internal Circuit Diagram
8.2 Softstart / Soft ramp down
During startup and ramp down the LED current is smoothly ramped up and ramped down. If the DCDC converter goes out of regulation
(measured by monitoring the voltage across the current sources), the ramp up is temporarily stopped in order for the DCDC to return to
regulation2.
1. If two LEDs are connected, it is possible to operate each of the two LEDs individually as the LED current can be
selected individually.
2. The actual value of the LED current setting can be readout by the register led_current_actual (see page 31) to allow
the camera processor to adopt to the actual operating conditions.
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AS3649
Datasheet - Detailed Description
www.ams.com/AS3649 1.0-2 12 - 39
8.3 4/1MHz Operating Mode Switching and Pulse Skipping
If freq_switch_on (see page 29)=1 and if led_current1>=40h or led_current2>=40h3 and current_boost=0, the DCDC converter always operates
in PWM mode (exception: PFM mode is allowed during startup) to reduce EMI in EMI sensitive systems. For high duty cycles close to 100% on-
time (maximum duty cycle) of the PMOS, the DCDC converter can switch into a 1MHz operating mode and maximum duty cycle to improve
efficiency for this load condition4. 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 predictable. If improved
efficiency is required, the fixed switching between 4MHz / 1MHz can be disabled by freq_switch_on (see page 29)=0. In this case pulseskip will
be used.
The modes are selected according to Table 4:
The internal circuit for switching between these two frequencies is shown in Figure 17 (for simplicity only a single current source is shown):
Figure 17. Internal circuit of 4MHz/1MHz selection
Note: If the voltage on VOUT1/2 exceeds VVOUTMAX, the DCDC will always skip pulses to limit the output voltage.
8.4 Protection and Fault Detection Functions
The protection functions protect the AS3649 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 sources are disabled5 by resetting mode_setting=006 and txmask_torch_mode=00.
3. Set register dcdc_skip_enable (see page 28)=1 if 4MHz forced operation shall be used below this LED current.
4. Efficiency compared to a 4MHz only DCDC converter forced to operate with minimum duty cycle.
Table 4. 4/1MHz switching and pulseskip operating modes
freq_switch_on dcdc_skip_enable led_current1>=40h or led_current2>=40h led_current1<40h and led_current2<40h
0 0 4MHz forced PWM operation (no 1MHz operation, no pulseskip)
0 1 4MHz, pulse skipping allowed, no 1MHz operation
10
4MHz/1Mhz forced PWM operation,
pulseskip not allowed1
1. If current_boost=1, freq_switch_on is set to ‘0’.
4MHz forced PWM operation (no 1MHz
operation, no pulseskip)
11 4MHz, pulse skipping allowed, no 1MHz
operation
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AS3649
Datasheet - Detailed Description
www.ams.com/AS3649 1.0-2 13 - 39
8.4.1 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_vds7., the DCDC converter is stopped, the current
sources are disabled and the bit fault_ovp (see page 29)8 is set9. In a dual LED configuration for the AS3649, if a single open LED is detected,
this LED is disabled, fault_ovp is set and the device continuous operation with the other LED.
Note: In PWM operating mode (mode_setting=01b), open LED detection is disabled (and fault_ovp is not set). The output voltage will never-
theless be kept below VVOUTMAX.
8.4.2 Short Circuit Protection
After the startup of the DCDC converter, the voltage on LED_OUT1/2 is continuously monitored and compared against VLEDSHORT if the LED
current is above 27.5mA (current_boost=0), 34.3mA (current_boost=1)10,11(see Figure 18). If the voltage on the LED (VFLED = LED_OUT1/2)
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 29) is set. In a dual LED configuration for the AS3649, if a single shorted LED is detected, this LED is disabled, fault_led_short is set
and the device continuous operation with the other LED.
Note: In PWM operating mode (mode_setting=01b), short circuit protection is disabled.
Figure 18. Short LED Detection
8.4.3 Overtemperature Protection
The junction temperature of the AS3649 is continuously monitored. If the temperature exceeds TOVTEMP, the DCDC is stopped, the current
sources are disabled (instantaneous) and the bit fault_overtemp (see page 29) is set (but the operating mode mode_setting is not changed). The
driver is automatically re-enabled12 once the junction temperature drops below TOVTEMP-TOVTEMPHYST.
8.4.4 TXMASK event occurred
If during flash, TXMASK current reduction is enabled (see TXMASK on page 15, configured by txmask_torch_mode=01) and a TXMASK event
happened (pin TXMASK/TORCH=1), the fault register bit fault_txmask (see page 28) is set.
5. Applies for all faults except TXMASK event occurred
6. Except for TXMASK event occurred and Overtemperature Protection
7. If overvoltage is reached, but none of the low_vds comparator(s) triggers, VOUT1/2 is still regulated below VVOUT-
MAX.
8. In indicator or low current PWM mode (mode_setting (see page 26)=01) the register fault_ovp is not set under an
overvoltage conditions. The output voltage is nevertheless kept below VVOUTMAX.
9. In constant voltage mode (5V generation, register bit const_v_mode=1) this fault is disabled.
10.To avoid errors in short LED detection for LEDs with a high leakage current
11. The LED short circuit protection is disabled in indicator mode (or low current mode using PWM) (mode_setting on
page 26=01b)
12.In constant voltage mode (const_v_mode=1) the DCDC will not be automatically re-enabled.
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AS3649
Datasheet - Detailed Description
www.ams.com/AS3649 1.0-2 14 - 39
8.4.5 Flash Timeout
If the flash is started a timeout timer is started in parallel. If the flash duration defined by the STROBE input (strobe_on=1 and strobe_type=1,
see Figure 25 on page 18) exceeds tFLASHTIMEOUT (adjustable by register flash_timeout (see page 26)), the DCDC is stopped and the flash
current sources (on pin LED_OUT1/2) are disabled (ramping down) and fault_timeout is set.
If the flash duration is defined by the timeout timer itself (strobe_on = 0, see Figure 23 on page 17), the register fault_timeout is set after the flash
has been finished.
8.4.6 Supply Undervoltage Protection
If the voltage on the pin VIN (=battery voltage) is or falls below VUVLO, the AS3649 is kept in shutdown state and all registers are set to their
default state.
8.4.7 NTC - Flash LED Overtemperature Protection
The ntc_on (see page 25)=1, the flash LED is protected by the AS3649 using an internal comparator connected to NTC and an current source
controlled by ntc_current (see page 25) (VNTC_TH, INTC as shown in Figure 16, “Internal Circuit Diagram,” on page 11); once it is triggered, the
DCDC is stopped, the current sources are disabled (instantaneous) and the bit fault_ntc (see page 28) is set.
As the external NTC cannot measure the LED temperature in real time during a high current flash pulse (the duration from heating up of the LED
until the NTC recognizes a too hot LED is usually too long), it is advisable to measure the LED temperature before the flash pulse (with the ADC
(see page 19) and ntc_current (see page 25)) and judge how much current can be driven through the LED (to be estimated depending on LED
heat sink and is usually specified by the LED manufacturer).
8.5 Operating Mode and Currents
The output currents and operating mode currents are selected according to the following table:
Table 5. Operating Mode and Current Settings
AS3649 Configuration Operating Mode and Currents
ON, SCL, SDA
TXMASK/TORCH
STROBE
mode_s
etting
(see
page 26)
Condition Mode LED_OUT1/2
Output current
ON=0
XX X X
Shutdown
All registers are reset to their
default values
0
ON=1; I2C commands are accepted on pins SCL and SDA
XX
00
txmask_torch_mode (see page
23) not 10 standby 0
0X txmask_torch_mode =10
1X txmask_torch_mode =10 external torch mode LED current is defined by the 6LSB1
bits of led_current1 and led_current2
XX 01 indicator mode or
low current pwm mode2
LED current is defined by the 6LSB
bits (bits 5...0) of led_current1 and
led_current2 pwm modulated defined
by register inct_pwm
(31.5kHz: 1/16...4/16) or 7.9kHz: 1/
64...3/64)
X X 10 torch light mode LED current is defined by the 6LSB2
bits (5...0) of led_current1 and
led_current2
XX
11
strobe_on (see page 28) = 0 flash mode;
flash duration defined by
flash_timeout (see page 26) LED current is defined by led_current1
and led_current2 - the current can be
reduced during flash, see Flash Current
Reductions below
X0->1 strobe_on = 1 and strobe_type
(see page 28) = 0
X1 strobe_on = 1 and
strobe_type = 1
flash mode;
flash duration defined by
STROBE input; timeout
defined by flash_timeout
AS3649
Datasheet - Detailed Description
www.ams.com/AS3649 1.0-2 15 - 39
8.5.1 Flash Current Reductions
TXMASK.
Usually the flash current is defined by the register led_current1 and led_current2. If the TXMASK/TORCH input is used and (configured by
txmask_torch_mode=01), the flash current is reduced to flash_txmask_current if TXMASK/TORCH=1.
Current Reduction by VIN Measurements in Flash Mode and Diagnostic Pulse.
Due to the high load of the flash driver and the ESR of the battery (especially critical at low temperatures), the voltage on the battery drops. If the
voltage drops below the reset threshold, the system would reset. To prevent this condition the AS3649 monitors the battery voltage and keeps it
above vin_low_v as follows:
If the voltage on VIN before the flash is below vin_low_v, the DCDC is not started at all. Otherwise during flash, if the voltage on VIN drops below
the threshold defined by vin_low_v, the flash current is reduced (or ramping of the current is stopped during flash current startup) and
status_uvlo is set. The timing for the reduction of the current is 2µs/LSB current change.
During the flash pulse the actual used current can be readout by the register led_current_actual.
After the flash pulse the minimum current can be readout by the register led_current_min - this allows to adjust the camera sensitivity (gain or
iso-settings) for the subsequent flash pulse (e.g. when using a pre-flash and a main flash pulse).
The internal circuit for low voltage current reductions are shown in Figure 19:
Figure 19. Low Voltage Current Reduction Internal Circuit
1. The MSB bit of this register not used to protect the LED; therefore the maximum torch light current = 1/4 * the maximum flash current
2. The low current mode is a general purpose PWM mode to drive less current through the LED in average, but keep the actual pulsed
current in a range where the light output from the LED is still specified. As only the 6 LSBs of led_current1 and led_current2 is used the
maximum current is limited to 1/4 of the maximum flash current.
Always keep led_current1 >= led_current2.
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AS3649
Datasheet - Detailed Description
www.ams.com/AS3649 1.0-2 16 - 39
A mobile phone camera flash system can trigger a diagnostic flash and a main-flash:
The diagnostic flash is initiated by the processor. After this diagnostic flash, the determined maximum flash current can be read back through the
I2C interface from register led_current_min (see page 30) and used for the setting for the main flash. Therefore the current in the main-flash is
constant and additionally the camera system can use this current for picture quality adjustments - the waveforms for this concept are shown in
Figure 20:
Figure 20. Low Voltage Current Reduction Waveform with Diagnostic-Flash and Main-Flash Phase
Short Diagnostic Pulse.
If the diagnostic flash should be short (e.g. 4ms) it is recommended to operate this diagnostic flash at a different vcompl_adj (see page 27) and
higher vin_low_v (see page 24) settings compared to the main flash as shown in Figure 21:
Figure 21. Low Voltage Current Reduction Waveform with Short Diagnostic-Flash and Main-Flash Phase
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AS3649
Datasheet - Detailed Description
www.ams.com/AS3649 1.0-2 17 - 39
The AS3649 efficiency reduction during main flash can be compensated during a short diagnostic flash by adjusting vcompl_adj as shown in
Figure 21. Reducing vin_low_v during main flash additionally takes into account a longer time constant of the battery for high loads and allows a
very short diagnostic pulse (only 4ms).
Using the ams AG linux software driver it is possible to calculate the maximum flash duration for a given operating condition (additionally using
TJUNCTION measured through the AS3649 ADC).
8.5.2 Load Balancing
To improve the efficiency of the AS3649 for LEDs with unmatched forward voltage and reduce the internal power dissipation of the AS3649, set
the bit load_balance_on=1. This bit can change the currents through the LEDs by up to +/-15% to match the forward voltage of the LED better as
shown in Figure 22:
Figure 22. Load Balancing
8.6 Flash Strobe Timings
The flash timing are defined as follows:
1. Flash duration defined by register flash_timeout and flash is started immediately when this mode is selected by the I2C command (see
Figure 23):
set strobe_on = 0, start the flash by setting mode_setting = 11b
2. Flash duration defined by register flash_timeout and flash started with a rising edge on pin STROBE (see Figure 24):
set strobe_on = 1 and strobe_type = 0
3. Flash start and timing defined by the pin STROBE; the flash duration is limited by the timeout timer defined by flash_timeout (see
Figure 25 and Figure 26):
set strobe_on = 1 and strobe_type = 1
Figure 23. AS3649 Flash Duration Defined by flash_timeout Without Using STROBE Input
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AS3649
Datasheet - Detailed Description
www.ams.com/AS3649 1.0-2 18 - 39
Figure 24. AS3649 Flash Duration Defined by flash_timeout, Starting Flash with STROBE Rising Edge
Figure 25. AS3649 Flash Duration and Start Defined by STROBE, Limited by flash_timeout; Timer Not Expired
Figure 26. AS3649 Flash Duration and Start Defined by STROBE, Limited by flash_timeout; Timer Expired
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AS3649
Datasheet - Detailed Description
www.ams.com/AS3649 1.0-2 19 - 39
8.7 ADC
The internal ADC is used to monitor LED temperature and DIE temperature. To operate the ADC, set the adc_channel (see page 27) and start
the conversion by adc_convert. When adc_convert returns to ‘0’ the result is available in register adc_result (see page 30) (Bits 9...7)and
adc_result_lsbs (Bits 1...0).
The DIE junction temperature measurement returns the value according to Table 6:
8.8 I2C Serial Data Bus
The AS3649 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 AS3649 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 AS3649 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 27):
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:
Bus Not Busy. Both data and clock lines remain HIGH.
Start Data Transfer. A change in the state of the data line, from HIGH to LOW, while the clock is HIGH, defines a START condition.
Stop Data Transfer. A change in the state of the data line, from LOW to HIGH, while the clock line is HIGH, defines the STOP condition.
Table 6. Junction Temperature Measurement ADC result
Junction Temperature - ºC ADC Return Value (10bit)
-30 352
-20 343
-10 334
0 325
10 316
20 306
30 297
40 287
50 278
60 268
70 259
80 249
90 239
100 229
110 219
120 209
130 199
140 189
150 179
AS3649
Datasheet - Detailed Description
www.ams.com/AS3649 1.0-2 20 - 39
Data Valid. The state of the data line represents valid data when, after a START condition, the data line is stable for the duration of the HIGH
period of the clock signal. The data on the line must be changed during the LOW period of the clock signal. There is one clock pulse per bit of
data.
Each data transfer is initiated with a START condition and terminated with a STOP condition. The number of data bytes transferred between
START and STOP conditions are not limited, and are determined by the master device. The information is transferred byte-wise and each
receiver acknowledges with a ninth bit.
Acknowledge. Each receiving device, when addressed, is obliged to generate an acknowledge after the reception of each byte. The master
device must generate an extra clock pulse that is associated with this acknowledge bit.
A device that acknowledges must pull down the SDA line during the acknowledge clock pulse in such a way that the SDA line is stable LOW
during the HIGH period of the acknowledge-related clock pulse. Of course, setup and hold times must be taken into account. A master must
signal an end of data to the slave by not generating an acknowledge bit on the last byte that has been clocked out of the slave. In this case, the
slave must leave the data line HIGH to enable the master to generate the STOP condition.
Figure 27. Data Transfer on I2C Serial Bus
Depending upon the state of the R/W bit, two types of data transfer are possible:
1. Data transfer from a master transmitter to a slave receiver. The first byte transmitted by the master is the slave address. Next
follows a number of data bytes. The slave returns an acknowledge bit after each received byte. Data is transferred with the most
significant bit (MSB) first.
2. Data transfer from a slave transmitter to a master receiver. The master transmits the first byte (the slave address). The slave then
returns an acknowledge bit, followed by the slave transmitting a number of data bytes. The master returns an acknowledge bit after all
received bytes other than the last byte. At the end of the last received byte, a “not acknowledge” is returned. The master device
generates all of the serial clock pulses and the START and STOP conditions. A transfer is ended with a STOP condition or with a
repeated START condition. Since a repeated START condition is also the beginning of the next serial transfer, the bus is not released.
Data is transferred with the most significant bit (MSB) first.
The AS3649 can operate in the following two modes:
1. Slave Receiver Mode (Write Mode): Serial data and clock are received through SDA and SCL. After each byte is received an
acknowledge bit is transmitted. START and STOP conditions are recognized as the beginning and end of a serial transfer. Address
recognition is performed by hardware after reception of the slave address and direction bit (see Figure 28). The slave address byte is
the first byte received after the master generates the START condition. The slave address byte contains the 7-bit AS3649 address,
which is 0110000, followed by the direction bit (R/W), which, for a write, is 0.13 After receiving and decoding the slave address byte the
device outputs an acknowledge on the SDA line. After the AS3649 acknowledges the slave address + write bit, the master transmits a
SLAVE
ADDRESS
ACKNOWLEDGEMENT SIG-
NAL FROM RECEIVER
ACKNOWLEDGEMENT SIG-
NAL FROM RECEIVER
REPEATED IF MORE
BYTES ARE TRANS-
FERRED
STOP CONDITION
OR REPEATED
START CONDITION
START
CONDITION
SCL
SDA
MSB
R/W
DIRECTION
BIT
ACK
126789123-7 89
AS3649
Datasheet - Detailed Description
www.ams.com/AS3649 1.0-2 21 - 39
register address to the AS3649. This sets the register pointer on the AS3649. The master may then transmit zero or more bytes of
data, with the AS3649 acknowledging each byte received. The address pointer will increment after each data byte is transferred. The
master generates a STOP condition to terminate the data write.
2. Slave Transmitter Mode (Read Mode): The first byte is received and handled as in the slave receiver mode. However, in this mode,
the direction bit indicates that the transfer direction is reversed. Serial data is transmitted on SDA by the AS3649 while the serial clock
is input on SCL. START and STOP conditions are recognized as the beginning and end of a serial transfer (Figure 29 and Figure 30).
The slave address byte is the first byte received after the master generates a START condition. The slave address byte contains the 7-
bit AS3649 address, which is 0110000, followed by the direction bit (R/W), which, for a read, is 1.14 After receiving and decoding the
slave address byte the device outputs an acknowledge on the SDA line. The AS3649 then begins to transmit data starting with the reg-
ister address pointed to by the register pointer. If the register pointer is not written to before the initiation of a read mode the first
address that is read is the last one stored in the register pointer. The AS3649 must receive a “not acknowledge” to end a read.
Figure 28. Data Write - Slave Receiver Mode
Figure 29. Data Read (from Current Pointer Location) - Slave Transmitter Mode
13.The address for writing to the AS3649 is 60h = 01100000b
14.The address for read mode from the AS3649 is 61h = 01100001b
S0110000 0 A XXXXXXXX AAAXXXXXXXX XXXXXXXX A
XXXXXXXX P
<Slave Address> <Word Address (n)> <Data(n)> <Data(n+1)> <Data(n+X)>
<RW>
S - Start
A - Acknowledge (ACK)
P - Stop
Data Transferred
(X + 1 Bytes + Acknowledge)
S0110000 1 A XXXXXXXX AAAXXXXXXXX XXXXXXXX NA
XXXXXXXX P
<Slave Address> <Data(n)> <Data(n+1)> <Data(n+X)>
<RW>
S - Start
A - Acknowledge (ACK)
P - Stop
NA - Not Acknowledge (NACK)
Data Transferred
(X + 1 Bytes + Acknowledge)
Note: Last data byte is followed by a NACK
<Data(n+2)>
AS3649
Datasheet - Detailed Description
www.ams.com/AS3649 1.0-2 22 - 39
Figure 30. Data Read (Write Pointer, Then Read) - Slave Receive and Transmit
8.9 Register Description
Table 7. ChipID Register
Addr: 0 ChipID Register
This register has a fixed ID
Bit Bit Name Default Access Description
2:0 version Xh R AS3649 chip version number
7:3 fixed_id 11000b R This is a fixed identification (e.g. to verify the I2C communication)
Table 8. Current Set LED1 Register
Addr: 1 Current Set LED1 Register
This register defines design versions
Bit Bit Name Default Access Description
7:0 led_current1 9Ch R/W
Define the current on pin LED_OUT1;
torch mode uses bits 5:0 of this current setting (max. 1/4 of full current
setting)
indicator or low current pwm mode uses only 5:0 of this current setting
(max. 1/4 of full current setting)
Note: Always keep led_current1 >= led_current2
0h 0mA
1h 7.8mA
2h 11.7mA
... ...
3Fh
250mA (maximum current for torch light mode, indicator or low
current pwm mode,
mode_setting=01 or 10)
... ...
7Fh 500mA
... ...
9Ch 613.3mA - default setting
... ...
FEh 996mA (1245mA1 if current_boost=1)
1. Only use current_boost=1 for currents > 1000mA(code >= CCh)
FFh 1000mA (1250mA1 if current_boost=1)
S0110000 0 A XXXXXXXX A1A
0110000
<Slave Address>
<Word Address (n)>
<Data(n+2)>
<RW>
S - Start
Sr - Repeated Start
A - Acknowledge (ACK)
P - Stop
NA - Not Acknowledge (NACK)
XXXXXXXX AAAXXXXXXXX XXXXXXXX NA
XXXXXXXX P
<Data(n)> <Data(n+1)> <Data(n+X)>
Sr
<RW>
Data Transferred
(X + 1 Bytes + Acknowledge)
Note: Last data byte is followed by a NACK
AS3649
Datasheet - Detailed Description
www.ams.com/AS3649 1.0-2 23 - 39
Table 9. Current Set LED2 Register
Addr: 2 Current Set LED2 Register
This register defines design versions
Bit Bit Name Default Access Description
7:0 led_current2 9Ch R/W
Define the current on pin LED_OUT2;
torch mode uses bits 5:0 of this current setting (max. 1/4 of full current
setting)
indicator or low current pwm mode uses only 5:0 of this current setting
(max. 1/4 of full current setting)
Note: Always keep led_current1 >= led_current2
0h 0mA
1h 7.8mA
2h 11.7mA
... ...
3Fh
250mA (maximum current for torch light mode, indicator or low
current pwm mode,
mode_setting=01 or 10)
... ...
7Fh 500mA
... ...
9Ch 613.3mA - default setting
... ...
FEh 996mA (1245mA1 if current_boost=1)
FFh 1000mA (1250mA1 if current_boost=1)
1. Only use current_boost=1 for currents > 1000mA(code >= CCh)
Table 10. TXMask Register
Addr: 3 TXMask Register
This register defines the TXMask settings and coil peak current
Bit Bit Name Default Access Description
1:0 txmask_torch_mode 00 R/W
Defines operating mode for input pin TXMASK/TORCH
00 pin has no effect
01
txmask-mode; during flash if TXMASK/TORCH=1, the LED
current is set to flash_txmask_current - (see TXMASK on page
15)
10
external torch mode: if TXMASK/TORCH=1 and
mode_setting=00, the AS3649is set into external torch mode
(LED current is defined by the 6LSB1 bits of led_current1 and
led_current2)
11 don’t use
3:2 coil_peak 10 R/W
Defines the maximum coil current (parameter ILIMIT)
00 ILIMIT = 2.5A
01 ILIMIT = 2.9A
10 ILIMIT = 3.3A
11 ILIMIT = 3.7A
AS3649
Datasheet - Detailed Description
www.ams.com/AS3649 1.0-2 24 - 39
7:4 flash_txmask_current26h R/W
Define the current on pin LED_OUT1 and LED_OUT2 (each current
source) in flash mode if txmask_torch_mode=01 and TXMASK/
TORCH=1
0h 0mA
1h 31mA (39mA if current_boost=1)
2h 63mA (78mA if current_boost=1)
3h 94mA (118mA if current_boost=1)
4h 125mA (157mA if current_boost=1)
5h 157mA (196mA if current_boost=1)
6h 188mA (235mA if current_boost=1) - default
7h 220mA (275mA if current_boost=1)
8h 251mA (314mA if current_boost=1)
9h 282mA (353mA if current_boost=1)
Ah 314mA (392mA if current_boost=1)
Bh 345mA (431mA if current_boost=1)
Ch 376mA (471mA if current_boost=1)
Dh 408mA (510mA if current_boost=1)
Eh 439mA (549mA if current_boost=1)
Fh 471mA (588mA if current_boost=1)
1. The MSB bit of this register not used to protect the LED; therefore the maximum current = 1/4 the maximum flash current
2. If current_boost=1, the LED current is increased by 25%.
Table 11. Low Voltage / NTC Register
Addr: 4 Low Voltage / NTC Register
This register defines the operating mode with low battery voltages
Bit Bit Name Default Access Description
2:0 vin_low_v 4h R/W
Voltage level on VIN where current reduction triggers during operation
(see Current Reduction by VIN Measurements in Flash Mode and
Diagnostic Pulse on page 15) - only in flash mode; if VIN drops below
this voltage during current ramp up, the current ramp up is stopped;
during operation the current is decreased until the voltage on VIN rises
above this threshold - status_uvlo is set
0h function is disabled
1h 3.0V
2h 3.07V
3h 3.14V
4h 3.22V - default
5h 3.3V
6h 3.38V
7h 3.47V
Table 10. TXMask Register (Continued)
Addr: 3 TXMask Register
This register defines the TXMask settings and coil peak current
Bit Bit Name Default Access Description
AS3649
Datasheet - Detailed Description
www.ams.com/AS3649 1.0-2 25 - 39
3ntc_on 0R/W
Enable overtemperature protection on pin NTC (internal comparator
comparing NTC to VNTC_TH)
0 disabled
1 enabled
7:4 ntc_current 8h R/W
Current through the NTC (INTC); it is enabled once the LED current
source (LED_OUT1/2) is operating and ntc_on=1 or the ADC measures
the LED temperature (see NTC - Flash LED Overtemperature Protection
on page 14)
0h
off;
can be used to use an external
current to bias the NTC
1h 40µA
2h 80µA
3h 120µA
4h 160µA
5h 200µA
6h 240µA
7h 280µA
8h 320µA - default
9h 360µA
Ah 400µA
Bh 440µA
Ch 480µA
Dh 520µA
Eh 560µA
Fh 600µA
Table 11. Low Voltage / NTC Register (Continued)
Addr: 4 Low Voltage / NTC Register
This register defines the operating mode with low battery voltages
Bit Bit Name Default Access Description
AS3649
Datasheet - Detailed Description
www.ams.com/AS3649 1.0-2 26 - 39
Table 12. Flash Timer Register
Addr: 5 Flash Timer Register
This register identifies the flash timer and timeout settings
Bit Bit Name Default Access Description
5:0 flash_timeout1
26h R/W
Define the duration of the flash timer and timeout timer
00h … 4ms
01h … 8ms
02h … 12ms
03h … 16ms
04h … 20ms
05h … 24ms
06h … 28ms
07h … 32ms
08h … 36ms
09h … 40ms
0Ah … 44ms
0Bh … 48ms
0Ch … 52ms
0Dh … 56ms
0Eh … 60ms
0Fh … 64ms
10h … 68ms
11h … 72ms
12h … 76ms
13h … 80ms
14h … 84ms
15h … 88ms
16h … 92ms
17h … 96ms
18h … 100ms
19h … 104ms
1Ah … 108ms
1Bh … 112ms
1Ch … 116ms
1Dh … 120ms
1Eh … 124ms
1Fh … 128ms
20h … 132ms
21h … 164ms
22h … 196ms
23h … 228ms
24h … 260ms
25h … 292ms
26h … 324ms
27h … 356ms
28h … 388ms
29h … 420ms
2Ah … 452ms
2Bh … 484ms
2Ch … 516ms
2Dh … 548ms
2Eh … 580ms
2Fh … 612ms
30h … 644ms
31h … 676ms
32h … 708ms
33h … 740ms
34h … 772ms
35h … 804ms
36h … 836ms
37h … 868ms
38h … 900ms
39h … 932ms
3Ah … 964ms
3Bh … 996ms
3Ch … 1028ms
3Dh … 1060ms
3Eh … 1092ms
3Fh … 1124ms
1. Internal calculation for codes above 20h: flash timeout [ms] = (flash_timeout-32) * 32 + 132 [ms]
Table 13. Control Register
Addr: 6 Control Register
This register identifies the operating mode and includes an all on/off bit
Bit Bit Name Default Access Description
1:0 mode_setting 00 R/W
Define the AS3649 operating mode - see Table 5, “Operating Mode and
Current Settings,” on page 14
00 standby/shutdown or external torch mode if
txmask_torch_mode (page 23)=10
01
indicator mode (or low current mode using PWM)
LED current is defined by the 6LSB1 bits of led_current1 and
led_current2 pwm modulated defined by register inct_pwm
(31.5kHz: 1/16...4/16, 7.9kHz: 1/64...3/64)
10
torch light mode:
LED current is defined by the 6LSB2 bits of led_current1 and
led_current2
11
flash mode:
LED current is defined by led_current1 and led_current2
(mode_setting is automatically cleared after a flash pulse)
AS3649
Datasheet - Detailed Description
www.ams.com/AS3649 1.0-2 27 - 39
3:2 min_on_increase 00 R/W
Increase min. on time of DCDC converter - use for diagnostic pulse, if
freq_switch_on=1.
If this register is not 00 and freq_switch_on=1, the DCDC converter will
use 4MHz operation forced PWM mode or pass-through mode but will
not switch to 1MHz operation
00 100% - default min. on time
01 108%
10 131%
11 157%
4force_dcdc_on 0R/W
Force DCDC operation even in pass-through mode - use for diagnostic
pulse, if freq_switch_on=1
0 DCDC is only enabled when needed; default
1DCDC is always enabled even when pass-though mode could be
used
7:5 vcompl_adj 000b R/W
Increase voltage compliance of current source for diagnostic pulses -
see Short Diagnostic Pulse on page 16
000 default - 0mV
001 14mV (26mV if current_boost=1)
010 29mV (51mV if current_boost=1)
011 43mV (77mV if current_boost=1)
100 57mV (103mV if current_boost=1)
101 71mV (129mV if current_boost=1)
110 85mV (154mV if current_boost=1)
111 100mV (180mV if current_boost=1)
1. The two MSB bits of this register are not used to protect the LED; therefore the maximum indicator (or low current mode using PWM)
light current = 1/4 the maximum flash current multiplied by the duty cycle defined by inct_pwm
2. The two MSB bits of this register not used to protect the LED; therefore the maximum torch light current = 1/4 the maximum flash cur-
rent
Table 14. Strobe Signalling / ADC Register
Addr: 7 Strobe Signalling / ADC Register
This register defines the flash current reducing and mode for STROBE
Bit Bit Name Default Access Description
3:0 adc_channel 000b R/W
Select ADC channel for conversion
000 NTC
001 TJUNC
010 VIN
Table 13. Control Register (Continued)
Addr: 6 Control Register
This register identifies the operating mode and includes an all on/off bit
Bit Bit Name Default Access Description
AS3649
Datasheet - Detailed Description
www.ams.com/AS3649 1.0-2 28 - 39
4adc_convert 0R/W
Start ADC conversion
0 ADC conversion finished
1Start ADC conversion - once finished the register bit is
automatically reset and the result is stored in adc_result
5dcdc_skip_enable 1R/W
Allow pulseskip operation of DCDC - see Table 4 on page 12
0 Disabled - force 4MHz (1MHz) operation
1Enabled - can use pulseskip1
6strobe_type 1R/W
Defines if the STROBE input is edge or level sensitive; see also bit
strobe_on (page 28)
0 STROBE input is edge sensitive
1 STROBE input is level sensitive
7strobe_on 1R/W
Enables the STROBE input
0 STROBE input disabled
1STROBE input enabled
in flash mode
1. Exception depending on freq_switch_on (see page 29) - see Table 4 on page 12
Table 15. Fault Register
Addr: 8
Fault Register
This register identifies all the different fault conditions and provide information about the
LED detection
Bit Bit Name Default Access Description
0status_uvlo 0R/sC1
an undervoltage event has happened - see Current Reduction by VIN
Measurements in Flash Mode and Diagnostic Pulse on page 15
0No
1Yes
1reserved 0 R reserved - don’t use
2fault_ntc 0R/sC1
LED overtemperature detection hit - see NTC - Flash LED
Overtemperature Protection on page 14
0No
1Yes
3fault_txmask 0R/sC1
TXMASK/TORCH event triggered during flash - see TXMASK event
occurred on page 13
0No
1Yes
4fault_timeout 0R/sC1
see Flash Timeout on page 14
0No fault
1 Flash timeout exceeded
Table 14. Strobe Signalling / ADC Register (Continued)
Addr: 7 Strobe Signalling / ADC Register
This register defines the flash current reducing and mode for STROBE
Bit Bit Name Default Access Description
AS3649
Datasheet - Detailed Description
www.ams.com/AS3649 1.0-2 29 - 39
5fault_overtemp 0R/sC1
see Overtemperature Protection on page 13
0No fault
1 Junction temperature limit has been exceeded
6fault_led_short 0R/sC1
see Short Circuit Protection on page 13
0No fault
1 A shorted LED is detected (pin LED_OUT1/2)
7fault_ovp 0R/sC1
see Overvoltage Protection on page 13
0No fault
1 An overvoltage condition is detected (pin VOUT)
1. R/sC = Read, self clear; after readout the register is automatically cleared
Table 16. PWM and Indicator Register
Addr: 9 PWM and Indicator Register
This register defines the PWM mode (e.g. for indicator) and 4/1MHz mode switching
Bit Bit Name Default Access Description
2:0 inct_pwm100 R/W
Define the AS3649 PWM with 31.5kHz or 7.9kHz operation for indicator
or low current mode (mode_setting=01)
000 1/16 duty cycle / 31.5kHz
001 2/16 duty cycle / 31.5kHz
010 3/16 duty cycle / 31.5kHz
011 4/16 duty cycle / 31.5kHz
100 1/64 duty cycle / 7.9kHz; needs const_v_mode=1 (additional
quiescent current)
101 2/64 duty cycle / 7.9kHz; needs const_v_mode=1
(additional quiescent current)
110 3/64 duty cycle / 7.9kHz; needs const_v_mode=1
(additional quiescent current)
111 (4/64 duty cycle / 7.9kHz) -
don’t use; use 000 setting instead
3freq_switch_on 0R/W
Exact frequency switching between 4MHz/1MHz for operation close to
maximum
pulsewidth - see Table 4 on page 12
0Pulseskip operation is allowed depending on dcdc_skip_enable
(see page 28)
1
if led_current1>=40h or led_current2>=40h and current_boost=0,
the DCDC is running at 4MHz or 1MHz and pulseskip is disabled -
results in improved noise performance
Table 15. Fault Register (Continued)
Addr: 8
Fault Register
This register identifies all the different fault conditions and provide information about the
LED detection
Bit Bit Name Default Access Description
AS3649
Datasheet - Detailed Description
www.ams.com/AS3649 1.0-2 30 - 39
4load_balance_on 0R/W
Balance the current sources (up to +/-15% of set current) to improve
application efficiency for unmatched LED forward voltages - see Load
Balancing on page 17
0 disabled
1 enabled
5const_v_mode 0R/W
Enables Constant output voltage mode
0 Normal operation defined by mode_setting
1
5V constant voltage mode on VOUT1/2;
LED current can be controlled by registers mode_setting,
led_current1 and led_current2 as in normal operating mode, but
the ramping up/down of the current sources is disabled
(instantaneous on/off of the LED current)
1. Using 31.5kHz modulation avoids audible noise on the output capacitor CVOUT
Table 17. ADC Result Register
Addr: Ah ADC Result Register
This register reports the actual set LED current
Bit Bit Name Default Access Description
7:0 adc_result NA R Result of ADC conversion for channel adc_channel
Table 18. ADC Result LSBs Register
Addr: Bh ADC Result LSBs Register
This register reports the actual set LED current
Bit Bit Name Default Access Description
1:0 adc_result_lsbs NA R Result of ADC conversion for channel adc_channel
Table 19. Minimum LED Current Register
Addr: Eh Minimum LED Current Register
This register reports the minimum LED current from the last operation cycle
Bit Bit Name Default Access Description
7:0 led_current_min123 00h R see Current Reduction by VIN Measurements in Flash Mode and
Diagnostic Pulse (see page 15) and Figure 20 on page 16
1. Only the current through LED_OUT1 is reported.
2. As the internal change of this register is asynchronous to the readout, it is recommended to readout the register after the flash pulse.
The register will store the minimum current through the LED after e.g. a previous flash. This current can be used for a subsequent flash
pulse for a safe operating range.
3. This register is only set if an actual current reduction happens (status_uvlo (see page 28)=1) otherwise led_current_min=0.
Table 16. PWM and Indicator Register (Continued)
Addr: 9 PWM and Indicator Register
This register defines the PWM mode (e.g. for indicator) and 4/1MHz mode switching
Bit Bit Name Default Access Description
AS3649
Datasheet - Detailed Description
www.ams.com/AS3649 1.0-2 31 - 39
Table 20. Actual LED Current Register
Addr: Fh Actual LED Current Register
This register reports the actual set LED current
Bit Bit Name Default Access Description
7:0 led_current_actual12 00h R
Actual set current through the current source (including all current
reductions as described in Flash Current Reductions (see page 15)
including LED current ramp up/down)
1. Only the current through LED_OUT1 is reported.
2. As the internal change of this register is asynchronous to the readout, it is recommended to readout the register twice and compare the
results.
Table 21. Unlock Register Register
Addr: 80h Unlock Register Register
Protection for register Current Boost
Bit Bit Name Default Access Description
7:0 unlock NA W Write 55h into this register to enable access to register 81h
Table 22. Current Boost Register
Addr: 81h Current Boost Register
Increase output current by 25%
Bit Bit Name Default Access Description
0current_boost10R/W
Boost all LED currents by 25%
0 all LED current are as described in the tables
1 all LED current are increased by 25%
1. Write 55h into register unlock (0x80) to enable access to this register (unlocking is only valid for the next I2C access) - required on any
write access to this register
AS3649
Datasheet - Detailed Description
www.ams.com/AS3649 1.0-2 32 - 39
8.10 Register Map
Table 23. Register Map 1
1. Always write’0’ to undefined register bits
Register Definition Addr Default Content
Name b7 b6 b5 b4 b3 b2 b1 b0
ChipID 0 Cxh fixed_id version
Current Set LED1 1 9Ch led_current1
Current Set LED2 2 9Ch led_current2
TXMask 3 68h flash_txmask_current coil_peak txmask_torch_mode
Low Voltage / NTC 4 84h ntc_current ntc_on vin_low_v
Flash Timer 5 26h flash_timeout
Control 6 00h vcompl_adj force_dcd
c_on min_on_increase mode_setting
Strobe Signalling /
ADC 7E0hstrobe_on strobe_ty
pe
dcdc_skip
_enable
adc_conv
ert adc_channel
Fault 8 00h fault_ovp fault_led_
short
fault_over
temp
fault_time
out
fault_txm
ask fault_ntc reserved status_uvl
o
PWM and Indicator 9 00h const_v_
mode
load_bala
nce_on
freq_switc
h_on inct_pwm
ADC Result Ah NA adc_result
ADC Result LSBs Bh NA adc_result_lsbs
Minimum LED Current Eh 00h led_current_min
Actual LED Current Fh 00h led_current_actual
Unlock Register 80h 00h unlock
Current Boost 81h 00h current_b
oost
AS3649
Datasheet - Application Information
www.ams.com/AS3649 1.0-2 33 - 39
9 Application Information
9.1 External Components
9.1.1 Input Capacitor CVIN
Low ESR input capacitors reduce input switching noise and reduce the peak current drawn from the battery. Ceramic capacitors are required for
input decoupling and should be located as close to the device as is practical.
If a different input capacitor is chosen, ensure similar ESR value and at least 3µF capacitance at the maximum input supply voltage. Larger
capacitor values (C) may be used without limitations.
Add a smaller capacitor in parallel to the input pin VIN (e.g. Murata GRM155R61C104, >50nF @ 3V, 0402 size).
9.1.2 Output Capacitor CVOUT
Low ESR capacitors should be used to minimize VOUT ripple. Multi-layer ceramic capacitors are recommended since they have extremely low
ESR and are available in small footprints. The capacitor should be located as close to the device as is practical.
X5R dielectric material is recommended due to their ability to maintain capacitance over wide voltage and temperature range.
If a different output capacitor is chosen, ensure similar ESR values and at least 4.2µF capacitance at 5V output voltage.
Table 24. Recommended Input Capacitor
Part Number CTC Code Rated
Voltage Size Manufacturer
GRM188R60J106ME47
10µ
>3µF@4.5V
>2µF@5.25V
X5R 6V3 0603 Murata
www.murata.com
LMK107BBJ106MA 10µ
>3µF@4.5V X5R 6V3 0603 Taiyo Yuden
www.t-yuden.com
Table 25. Recommended Output Capacitor
Part Number CTC Code Rated
Voltage Size Manufacturer
GRM219R61A106ME47 10µF +/-10%
>4.2µF@5V X5R 10V 0805 (2.0x1.25x0.85mm
max 1mm height)
Murata
www.murata.com
GRM21BR60J226M1
1. Use only for VLED < 4.1V
22µF
>4.2µF@4.5V X5R 6.3V
0805
(2.0x1.25x1.25mm
max. 1.4mm height)
GRM188R60J106ME842
2. Use only for VLED < 3.75V
10µF +/-20%
>4.2µF@4V X5R 6.3V
0603
(1.6x0.8x0.85mm
max. 0.95mm height)
AS3649
Datasheet - Application Information
www.ams.com/AS3649 1.0-2 34 - 39
9.1.3 Inductor LDCDC
The fast switching frequency (4MHz) of the AS3649 allows for the use of small SMDs for the external inductor. The saturation current
ISATURATION should be chosen to be above the maximum value of ILIMIT15. The inductor should have very low DC resistance (DCR) to reduce
the I2R power losses - high DCR values will reduce efficiency.
If a different inductor is chosen, ensure similar DCR values and at least0.6µH inductance at ILIMIT.
9.1.4 Thermistor (NTC)
The NTC is used to protect the LED against overheating (hardware protection inside the AS3649, which works without any software - see NTC -
Flash LED Overtemperature Protection on page 14).
The thermistor has to be thermally coupled to the LED (and therefore as close as possible to the LED) and it shall not share the same ground
connection as the LED return ground (if they share the same ground connection the high current through the LED will offset the measurement of
the NTC).
It is recommended to use 220k resistance for a detection threshold of 125ºC, 100k for 110ºC and 68k for 80ºC LED temperature detection
threshold.
15.Can be adjusted in I2C mode with register coil_peak (see page 23)
Table 26. Recommended Inductor
Part Number LDCR ISATURATION Size Manufacturer
LQM32PN1R0MG0 1.0µH
>0.6µH @ 3.0A 60m3.0A1
1. Flash pattern: 200ms/3A, 200ms pause, 200ms/3A, 2s then repeat again (no limit on the number of total cycles)
Alternative pattern with 1000ms/1.6A, 200ms pause, 200ms/3A, 200ms pause, 200ms/3A, 2s then repeat again. (no limit on the number
of total cycles). Use only up to coil_peak=2.9A setting
3.2x2.5x0.9mm
max 1.0mm
height
Murata
www.murata.com
SPM4012T-1R0M 1.0µH +/-20% 38m 4.57A
4.4x4.1x1.2
mm
height is max TDK
www.tdk.com
SPM3012T-1R0M 1.0µH +/-20% 57m
+/-10% 3.4A2
2. Inductance changes by -30%, use only up to coil_peak=3.3A setting
3.2x3x1.2
mm
height is max
CIG32W1R0MNE
1.0µH
>0.7µH @ 2.7A
>0.6µH @ 3.0A
60m
+/-25% 3.0A43.2x2.5mm
max 1.0mm
height
Samsung Electro-Mechancs
www.sem.samsung.co.kr
CKP3225N1R0M 1.0µH
>0.6µH @ 3.0A <60m3.0A43.2x2.5x0.9mm
max 1.0mm
height
Taiyo Yuden
www.t-yuden.com
NRH2412T1R0N 1.0µH
>0.6µH @ 2.5A 77m2.5A3
3. Use only for coil_peak=2.5A setting.
2.4x2.4x1.2mm
(height is max.)
MAMK2520T1R0M 1.0µH
>0.6µH @ 2.75A 45m3.1A4
4. Use only up to coil_peak=2.9A setting.
2.5x2.0x1.2mm
height is max
Table 27. Recommended Thermistors
Part Number Resistance @ 25ºC B-constant 25/50ºC Size Manufacturer
NCP03WL224E05RL 220k +/-3% 4485K +/-1% 0201
Murata
www.murata.com
NCP03WL104E05RL 100k +/-3% 4485K +/-1%
NCP15WF104F03RC 100k0402
NCP15WL683J03RC 68k
AS3649
Datasheet - Application Information
www.ams.com/AS3649 1.0-2 35 - 39
9.2 PCB Layout Guideline
The high speed operation requires proper layout for optimum performance. Route the power traces first and try to minimize the area and wire
length of the two high frequency/high current loops:
Loop1: CVIN/CVIN2 - LDCDC - pin SW1/2 - pin GND - CVIN/CVIN2
Loop2: CVIN/CVIN2 - LDCDC - pin SW1/2 - pin VOUT1/2 - CVOUT - pin GND - CVIN/CVIN2
At the pin GND a single via (or more vias, which are closely combined) connects to the common ground plane. This via(s) will isolate the DCDC
high frequency currents from the common ground (as most high frequency current will flow between Loop1 and Loop2 and will not pass the
ground plane) - see the ‘island’ in Figure 31.
Figure 31. Layout Recommendation
Note: If component placement rules allow, move all components close to the AS3649 to reduce the area and length of Loop1 and Loop2.
It is recommended to use the main ground plane for the LED ground connections (improved thermal performance of the LEDs) - it is
recommend to use a separate ground line as shown Figure 31 for the ground connection of the NTC (this avoids errors for the temper-
ature measurement of the LEDs due to the high LED current in the main ground plane).
Keep the LED path (from pin LED_OUT1/2 to the LED and the ground return path) below 10cm (represents an inductance of less than
100nH).
An additional 100nF (e.g. Murata GRM155R61C104, >50nF @ 3V, 0402 size) capacitor CVIN2 in parallel to CVIN is recommended to filter high
frequency noise for the power supply of AS3649. This capacitor should be as close as possible to the AGND/VIN pins of AS3649.
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AS3649
Datasheet - Application Information
www.ams.com/AS3649 1.0-2 36 - 39
9.3 5V Operating Mode
The AS3649 can be used to power a 5V system (e.g. audio amplifier). The operating mode is selected by setting register bit
const_v_mode (page 30)=1.
Note: There is always a diode between VIN and VOUT1/2 due to the internal circuit. Therefore VOUT1/2 cannot be completely switched off
Figure 32. 5V Operating Mode
AS3649
AS3649
Datasheet - Package Drawings and Markings
www.ams.com/AS3649 1.0-2 37 - 39
10 Package Drawings and Markings
Figure 33. WL-CSP16 Marking
Note:
Line 1: ams AG logo
Line 2: AS3649
Line 3: <Code>
Encoded Datecode (4 characters)
Figure 34. WL-CSP16 Package Dimensions
The coplanarity of the balls is 40µm.
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AS3649
Datasheet - Ordering Information
www.ams.com/AS3649 1.0-2 38 - 39
11 Ordering Information
The devices are available as the standard products shown in Table 28.
Z Temperature Range: -30ºC - 85ºC
WL Package: Wafer Level Chip Scale Package (WL-CSP) 2.06x2.02x0.6mm
T Delivery Form: Tape & Reel
Note: All products are RoHS compliant and ams green.
Buy our products or get free samples online at www.ams.com/ICdirect
Technical Support is available at www.ams.com/Technical-Support
For further information and requests, email us at sales@ams.com
(or) find your local distributor at www.ams.com/distributor
Table 28. Ordering Information
Ordering Code Description Delivery Form Package
AS3649-ZWLT 2500mA High Current LED Flash Driver Tape & Reel
16-pin WL-CSP
(2.06x2.02x0.6mm)
0.5mm pitch
RoHS compliant / Pb-Free / Green
AS3649
Datasheet - Ordering Information
www.ams.com/AS3649 1.0-2 39 - 39
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reserved. The material herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the
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devices from patent infringement. ams AG reserves the right to change specifications and prices at any time and without notice. Therefore, prior
to designing this product into a system, it is necessary to check with ams AG for current information. This product is intended for use in normal
commercial applications. Applications requiring extended temperature range, unusual environmental requirements, or high reliability
applications, such as military, medical life-support or life-sustaining equipment are specifically not recommended without additional processing
by ams AG for each application. For shipments of less than 100 parts the manufacturing flow might show deviations from the standard
production flow, such as test flow or test location.
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