LM3556_15 Datasheet, PDF (19/39 Pages) Texas Instruments – Synchronous Boost LED Flash Driver With High-Side Current Source

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7.6 Register Maps
7.6.1 Register Descriptions
REGISTER NAME
Silicon Revision and Filter Time Register
IVFM Mode Register
NTC Settings Register
Indicator Ramp Time Register
Indicator Blinking Register
Indicator Period Count Register
Torch Ramp Time Register
Configuration Register
Flash Features Register
Current Control Register
Enable Register
Flags Register
LM3556
SNVS796D – AUGUST 2011 – REVISED OCTOBER 2015
INTERNAL HEX ADDRESS
0x00
0x01
0x02
0x03
0x04
0x05
0x06
0x07
0x08
0x09
0x0A
0x0B
POWER ON/RESET VALUE
0x04
0x80
0x12
0x00
0x00
0x00
0x00
0x78
0xD2
0x0F
0x00
0x00
7.6.1.1 Silicon Revision and Filter Time Register (0x00)
Bit 7
RFU
Bit 6
RFU
Table 2. Silicon Revision and Filter Time Register Description
Bit 5
RFU
Bit 4
Bit 3
IVFM Filter Times
'00' = 1/2 of the Current Step Time
'01' = 256 µs
'10' =512 µs
'11' = 1024 µs
Bit 2
Bit 1
Bit 0
Bits available for Silicon Revision
Current Value = '100'
7.6.1.2 Input Voltage Flash Monitor (IVFM) Mode Register (0x01)
Table 3. Input Voltage Flash Monitor (IVFM) Mode Register Description
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
1 = UVLO EN
(default)
Hysteresis Level
00 = 50 mV (default)
01 = 100 mV
10 = 150 mV
11 = Hysteresis Disabled
IVM-D (Down) Threshold
000 = 2.9 V (default)
001 = 3 V
010 = 3.1 V
011 = 3.2 V
100 = 3.3 V
101 = 3.4 V
110 = 3.5 V
111 = 3.6 V
IVFM Adjust Mode
00 = Report Mode (default)
01 = Stop and Hold Mode
10 = Down Mode
11 = Up and Down Mode
00 = Report Mode Sets IVFM flag in Flags Register upon crossing IVM-D line Only. Does not adjust current.
01 = Stop and Hold Mode Stops current ramp and holds the level for the remaining flash if V_IN crosses IVM-D
Line. Sets IVFM flag in Flags Register upon crossing IVM-D line.
10 = Down Mode Adjusts current down if V_IN crosses IVM-D Line and stops decreasing once V_IN rises above the
IVM-D line plus the IVFM hystersis setting. The LM3556 decreases the current throughout the flash
pulse anytime the input voltage falls below the IVM-D line, and not just once. The flash current does
not increase again until the next flash. Sets IVFM flag in Flags Register upon crossing IVM-D Line.
11 = Up and Down Mode Adjusts current down if V_IN crosses IVM-D Line and adjusts current up if V_IN rises
above the IVM-D line plus the IVFM hystersis setting. In this mode, the current continually adjusts
with the rising and falling of the input voltage throughout the entire flash pulse. Sets IVFM flag in
Flags Register upon crossing IVM-D Line.
UVLO EN
If enabled and V_IN drops below 2.8 V, the LM3556 enters standby and sets the UVLO flag in the
Flags Register. Enabled = ‘1’, Disabled = ‘0’
IVM-U = IVM-D + IVFM Hysteresis
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