Datasheet
ADP1649 Data Sheet
Rev. 0 | Page 14 of 28
Table 8. V
DD
Level at Which the V
BAT
Low Function Is Enabled
Bit Name V
DD
Level
V_VB_LO 000 = disabled (default)
001 = 3.3 V
010 = 3.35 V
011 = 3.4 V
100 = 3.45 V
101 = 3.5 V
110 = 3.55 V
111 = 3.6 V
PROGRAMMABLE BATTERY DC CURRENT LIMIT
The ADP1649 has four optional programmable input dc current
limits that limit the maximum input battery current over all con-
ditions. This allows use of higher LED currents in a system with
significant variation in LED forward voltage (V
F
) and supply
battery voltage without risk of exceeding the current allocated
to the flash.
Table 9. Input DC Current
Limit Setting the LED Current
Bit Name Current Limit
IL_DC 00 = 1.5 A
01 = 1.75 A
10 = 2.0 A (default)
11 = reserved
During startup of the flash, if the battery current does not reach
the dc current limit, the LED current is set to the current value
of the I_FL bits. If the battery current reaches the programmed
dc current limit on startup, the LED current does not increase
further. The dc current limit flag is set in the fault information
register. The I_FL bits in Register 0x03 are set to the automatically
reduced current-limit LED current and are available for readback.
Figure 32. DC Current-Limit Operation in a Low Battery, High LED V
F
Case
The camera system shown in Figure 33 can adjust the image
sensor settings based on the known reduced LED current for a
low battery and a high V
F
LED.
Figure 33. Use of the DC Current Limit in an Optimized Camera System
REG 0x02, FL_TIM = XXXX ms
REG 0x03, I_FL = XXXXX mA
REG 0x07 IL_DC_EN = 1
REG 0x07 IL_DC = XX A
I
2
C DATA BUS
STROBE
ADP1649 SETS OUTPUT_EN TO 0.
ADP1649 SETS LED_MOD TO 00.
NO LIMIT LED CURRENT
ACTUAL LED CURRENT
ADP1649 SETS FL_IDC (REG 0x05) TO 1.
ADP1649 SETS I_FL TO ACTUAL LED CURRENT.
REG 0x04, OUTPUT_EN = 1
STR_LV = 1
LED_MOD = 11
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SELECT FLASH CURRENT
SELECT MAX BATTERY CURRENT
PREFLASH STROBE
DC LIMIT HIT?
LED CURRENT =
PROGAMMED LED
CURRENT
NO
LED CURRENT =
REDUCED LED CURRENT
YES
BATTERY CURRENT =
PROGRAMMED DC LIMIT
I
2
C READ LED CURRENT
ADJUST IMAGE SENSOR
STROBE
STROBE
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