LM3556_15 Datasheet, PDF (21/39 Pages) Texas Instruments – Synchronous Boost LED Flash Driver With High-Side Current Source

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7.6.1.3 NTC Settings Register (0x02)
LM3556
SNVS796D – AUGUST 2011 – REVISED OCTOBER 2015
Bit 7
RFU
Bit 6
RFU
Table 4. NTC Settings Register Description
Bit 5
NTC Event
Level
0 = Go to
standby
(default)
1 = Reduce
to minimum
torch current
Bit 4
Bit 3
NTC Trip Thresholds
000 = 200 mV
001 = 300 mV
010 = 400 mV
011 = 50 mV
100 = 600 mV (default)
101 = 700 mV
110 = 800 mV
111 = 900 mV
Bit 2
Bit 1
Bit 0
NTC Bias Current Level
00 = 25 µA
01 = 50 µA
10 = 75 µA (default)
11 = 100 µA
V_IN
TEMP
NTC
NTC Control Block
I_NTC
-
V_{TRIP +}
Control
Logic
Figure 36. NTC Control Block
The TEMP node is connected to an NTC resistor as shown in Figure 36 above. A constant current source from
the input is connected to this node. Any change in the voltage because of a change in the resistance of the NTC
resistor is compared to a set V_TRIP. The trip thresholds are selected by Bits[4:2] of the NTC Register. The output
of the Control Logic upon an NTC trip is selected through Bit[5].
7.6.1.4 Indicator Ramp Time Indicator (0x03)
Bit 7
RFU
Bit 6
RFU
Table 5. Indicator Ramp Time Indicator Description
Bit 5
Bit 4
Bit 3
Indicator Ramp-Up Time (t_R)
000 = 16 ms (default)
001 = 32 ms
010 = 64 ms
011 = 128 ms
100 = 256 ms
101 = 512 ms
110 = 1.024 s
111 = 2.048 s
Bit 2
Bit 1
Bit 0
Indicator Ramp-Down Time (t_F)
000 = 16 ms (default)
001 = 32 ms
010 = 64 ms
011 = 128 ms
100 = 256 ms
101 = 512 ms
110 = 1.024 s
111 = 2.048 s
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