LM26LV (GAIN2)

(Trip 70qC to 110qC)

PP/PC

Imager

LM3553

FEN

Tx

SCL

SDA

OVERTEMP

LM3553

www.ti.com

SNVS414B – FEBRUARY 2008 – REVISED MAY 2013

THERMAL PROTECTION

Internal thermal protection circuitry disables the LM3553 when the junction temperature exceeds 150°C (typ.).

This feature protects the device from being damaged by high die temperatures that might otherwise result from

excessive power dissipation. The device will recover and operate normally when the junction temperature falls

below 140°C (typ.). It is important that the board layout provide good thermal conduction to keep the junction

temperature within the specified operating ratings.

Figure 22. External Temperature Sensor Diagram

Using an external temperature sensor, such as the LM26LV, can help aid in the thermal protection of the flash

LEDs as well as other components in a design. Connecting the OVERTEMP pin of the LM26LV to the TX pin on

the LM3553 prevents the high current flash from turning on when the set temperature threshold on the LM26LV

is reached. When the temperature trip point is reached, the OVERTEMP pin on the LM26LV will transition from a

'0' to a '1' which in turn enables the LM3553's TX mode. When a flash is instantiated by either the imager or

microprocessor, the LM3553 will only allow the flash LED current to reach the current level set in the Torch

Current register as long as the temperature sensor is registering an over-temperature condition. Placing the

temperature sensor close to the flash LEDs can help prevent the LEDs from reaching a temperature above the

maximum specified limit due to high-current flashing in a high temperature ambient environment.

Copyright © 2008–2013, Texas Instruments Incorporated

Submit Documentation Feedback

17

Product Folder Links: LM3553