Control

Logic

NTC Control Block

TEMP

NTC

+

-

LM3556

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SNVS796D – AUGUST 2011 – REVISED OCTOBER 2015

7.6.1.3 NTC Settings Register (0x02)

Table 4. NTC Settings Register Description

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

RFU

RFU

NTC Event

NTC Trip Thresholds

NTC Bias Current Level

Level

000 = 200 mV

00 = 25 µA

0 = Go to

001 = 300 mV

01 = 50 µA

standby

010 = 400 mV

10 = 75 µA (default)

(default)

011 = 50 mV

11 = 100 µA

1 = Reduce

100 = 600 mV (default)

to minimum

101 = 700 mV

torch current

110 = 800 mV

111 = 900 mV

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

of the Control Logic upon an NTC trip is selected through Bit[5].

7.6.1.4 Indicator Ramp Time Indicator (0x03)

Table 5. Indicator Ramp Time Indicator Description

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

RFU

RFU

000 = 16 ms (default)

000 = 16 ms (default)

001 = 32 ms

001 = 32 ms

010 = 64 ms

010 = 64 ms

011 = 128 ms

011 = 128 ms

100 = 256 ms

100 = 256 ms

101 = 512 ms

101 = 512 ms

110 = 1.024 s

110 = 1.024 s

111 = 2.048 s

111 = 2.048 s

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