Bit 0

Bit 1

Bit 2

Bit 3

Bit 4

Bit 5

TX1/

TORCH

Bit 7

Bit 6

MSB

LSB

Configuration Register 1

Register Address 0xE0

TX2

Polarity

ENVM/TX2

HYST

Ext Flash

Inhibit

OV

LL

Disable

LEDI/NTC

LM3554

SNVS549A – JUNE 2009 – REVISED APRIL 2011

www.ti.com

Table 5. Flags Register Bit Settings

Bit 6 (Unused)

Bit 5 (LED

Bit 4 (TX2

Bit 3 (TX1

Bit 2 (Led

Bit 1 (Thermal

Bit 0 (Flash

Monitor Fault

Thermal

Interrupt)

Interrupt )

Fault)

Shutdown)

Timeout)

Fault)

Fault)

0=No Fault at

Not Used

0=LEDI/NTC

0=ENVM/TX2

0=TX1/TORCH

0 = Proper

0 = Die

0 = Flash

VIN (default)

(Reads Back

pin is above

has not

has not changed

LED Operation

Temperature

TimeOut did not

'1')

changed state

state (default)

(default)

below Thermal

expire (default)

(default)

Shutdown Limit

(default)

1=Input

1=LEDI/NTC

1=ENVM/TX2

1=TX1/TORCH

1 = LED Failed

1 = Die

1 = Flash

Voltage

has fallen

has changed

pin has changed

(Open or Short

Temperature

TimeOut

Monitor is

below

state (TX2

state (TX1 mode

has crossed

Expired

enabled and

mode only)

only)

the Thermal

VIN has fallen

mode only)

Shutdown

below the

Threshold

programmed

threshold

CONFIGURATION REGISTER 1

Configuration Register 1 holds the light load disable bit, the voltage mode select bit (OV), the external flash

inhibit bit, the control bit for the LEDI/NTC pin, the control bit for ENVM to TX2 mode, the polarity selection bit for

the TX2 input, and the control bit for the TX1/TORCH bit (see Figure 23 and Table 6).

Figure 23. Configuration Register1 Description

Table 6. Configuration Register 1 Bit Settings

Bit 7

Bit 6 (TX2

Bit 5

Bit 4 (N/A)

Bit 3

Bit 2 (External

Bit 1 (OV,

Bit 0

(Hardware

Polarity)

(ENVM/TX2)

(LEDI/NTC)

Flash Inhibit)

Output

(Disable Light

Torch Mode

Voltage

Load )

Enable)

Select)

0 =

0 = ENVM/TX2

0 = ENVM

Reads Back '0'

0 = LEDI/NTC

0 = STROBE

0 = Voltage

0 = Light load

TX1/TORCH is

pin is an active

Mode The

pin in Indicator

Input Enabled

Mode output

comparator is

a TX1 flash

low Flash

ENVM/TX2 pin

mode (default)

(default)

voltage is 4.5V

enabled. The

interrupt input

inhibit

is a logic input

LM3554 will go

(default)

to enable

into PFM mode

Voltage Mode.

at light load

A high on

(default).

ENVM/TX2 will

force Voltage

Output Mode

(default)

1 =

1 = ENVM/TX2

1 = TX2 Mode

1 = LEDI/NTC

1 = STROBE

1 = Voltage

1 = Light load

TX1/TORCH

pin is an active

The ENVM/TX2

pin in Thermal

Input Disabled

Mode output

comparator is

pin is a

high Flash

is a Power

Comparator

voltage is 5V

disabled. The

hardware

inhibit (default)

Amplifier

Mode. Indicator

(default)

LM3554 will not

TORCH enable

Synchronization

current is

go into PFM

input. A high on

disabled.

mode at light

ENVM/TX2 will

load.

force the

LM3554 from

Flash to Torch

mode.

32

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