LM3556

SNVS796C – AUGUST 2011 – REVISED APRIL 2013

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Enable Register (0x0A)

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

TX Pin Enable

STROBE Pin

TORCH Pin

PreCharge Mode

Pass-Mode

Mode Bits: M1, M0

NTC Enable

0 = Disabled

Enable

Enable

Enable

Only Enable

00 = Standby (default)

0 = Disabled

(default)

0 = Disabled

0 = Disabled

0 = Normal

0 = Normal

01 = Indicator

(default)

1 = Enabled

(default)

(default)

(default)

(default)

10 = Torch

1 = Enabled

1 = Enabled

1 = Enabled

1 = PreCharge

1 = Pass Only

11 = Flash

Enable Register (8 Bits)

NTC EN Enables NTC Block.

TX EN Allows TX events to change the current.

Strobe EN Enables Strobe Pin to start a Flash Event.

Torch EN Enables Torch Pin to start a Torch Event.

PreCharge Mode EN Enables Pass Mode to pre-charge the output cap.

Pass-Only Mode EN Only allows Pass Mode and disallows Boost Mode.

If Pass-Only Mode is enabled during any LED mode (Indicator, Torch or Flash), it will remain enabled until

the LM3556 enters the standby state regardless of whether the Pass-Only Mode bit is reset or not during

the following command.

Two-Mode Bits

00–Standby Off

01–Indicator Sets Indicator Mode. Default Indicator Mode uses external pattern on TORCH Pin.

Flags Register (0x0B)

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

TX Event

NTC Trip

IVFM

UVLO

OVP

LED or VOUT

Thermal

Flash Time-out

0 = Default

0 = Default

0 = Default

0 = Default

0 = Default

Short Fault

Shutdown

0 = Default

0 = Default

0 = Default

TX Event Flag TX Event occurred.

NTC Trip Flag NTC Threshold crossed.

IVFM Flag IVFM block reported and/or adjusted LED current.

UVLO Fault UVLO Threshold crossed.

OVP Flag Over-voltage Protection tripped. Open Output cap or open LED.

LED Short Fault LED Short detected.

Thermal Shutdown Fault LM3556 die temperature reached thermal shutdown value.

Time-Out Flag Flash Timer tripped

Note: Faults require a read-back of the “Flags Register” to resume operation. Flags report an event

occurred, but do not inhibit future functionality. A read-back of the Flags Register will only be updated

again if the fault or flags is still present upon a restart.

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