Datasheet
Data Sheet ADP1649
Rev. 0 | Page 13 of 28
TORCH TO FLASH MODE
The driver can move directly from external torch mode (using
GPIO1) to flash mode by bringing the STROBE pin high before
bringing the GPIO1 pin (set for the torch mode) low. Bringing
torch low before the STROBE pin goes high prevents the flash
from firing when the STROBE pin goes high.
The ADP1649 returns to standby mode after a successful flash
and sets OUTPUT_EN = 0.
Figure 29. Enabling Flash Mode from External Torch Mode
TxMASK OPERATION
When the ADP1649 is in flash mode, the TxMASK1 and the
TxMASK2 functions reduce the battery load in response to the
system enabling a power amplifier. The device remains in flash
mode, but the LED driver output current reduces to the pro-
grammed TxMASK light level in less than 21 µs.
Figure 30. TxMASK1 Operation During Flash (Level Sensitive) Mode
The device selects the TxMASK1 or TxMASK2 current level
based on whether the TxMASK1 or TxMASK2 input is used.
Anytime TxMASK1 or TxMASK2 is brought high during a
flash event, a flag is set in the fault information register. To avoid
overshoots on the battery current, when the TxMASK signal goes
low again, the LED current returns to the full flash level in a
controlled manner. If both TxMASK inputs are set high
simultaneously, the TxMASK1 current level is used.
FREQUENCY FOLDBACK
Frequency foldback is an optional mode that optimizes efficiency
by reducing the switching frequency to 1.5 MHz when VIN is
slightly less than VOUT. Enable frequency foldback by setting
FREQ_FB = 1 in Register 0x04.
INDICATOR LED DRIVER
The indicator LED driver on GPIO2 provides a programmable
current source of between 2.75 mA and 11 mA for driving a red
privacy LED; the I_ILED bits in Register 0x07 program the current
level. The circuit consists of a programmable current source and
a monitoring circuit that uses comparators to determine whether
the indicator LED is short circuit or open circuit. The threshold
for detection of a short circuit is 1.2 V (maximum), and for an
open circuit, the threshold is 2.45 V (minimum). The indicator
LED must not be used at the same time as a flash or an assist/
torch event.
LOW BATTERY LED CURRENT FOLDBACK
As the battery discharges, the lower battery voltage results in
higher peak currents through the battery ESR, which may cause
early shutdown of the phone. The ADP1649 features an optional
low battery detection option that reduces the flash current (to a
programmable level) when the battery voltage falls below a
programmable level. Set V_VB_LO = 000 to disable the low
battery current foldback (see Table 8 for details).
Figure 31. Register 0x09 Sets the Battery Voltage Threshold Level and the
Reduced LED Current Level
LED CURRENT
REG 0x02, FL_TIM = XXXX ms
IO1_CFG = 01, TORCH
REG 0x03, I_TOR = XXX mA
REG 0x03, I_FL = XXXXX mA
REG 0x04, OUTPUT_EN = 1
STR_LV = 1
LED_MOD = 00
I
2
C DATA BUS
0A
I
FLASH
STROBE
ADP1649 SETS OUTPUT_EN TO 0
I
ASSIST
TORCH
10779-029
LED CURRENT
REG 0x02, IO1_CFG = 10
FL_TIM = XXXX ms
REG 0x03, I_FL = XXXXX mA
REG 0x06, I_TX1 = XXXX mA
REG 0x04, OUTPUT_EN = 1
STR_LV = 1
LED_MOD = 11
I
2
C DATA BUS
0A
I
FLASH
STROBE
ADP1649 SETS OUTPUT_EN TO 0.
ADP1649 SETS LED_MOD TO 00.
I
TxMASK1
TxMASK1
(GPIO1)
FL_TX1 = 1
10779-030
LED CURRENT
REG 0x09, I_VB_LO = XXXX mA
V_VB_LO = XXX V
I
2
C DATA BUS
0
A
I
FLASH
STROBE
ADP1649 SETS OUTPUT_EN TO 0.
ADP1649 SETS LED_MOD TO 00.
I
I_VB_LO
VIN
V
V_VB_LO
REG 0x04, OUTPUT_EN = 1
LED_MOD = 10
FL_VB_LO = 1
50mV HYS
GLITCH < 50µs IGNORED
10779-031