TPS61311 datasheet(19/57 Pages) TI

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TPS61310, TPS61311

www.ti.com

SLVS978C – MARCH 2010 – REVISED NOVEMBER 2012

DETAILED DESCRIPTION

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OPERATION

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VIDEO LIGHT AND FLASH OPERATION

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VOLTAGE MODE

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PRIVACY INDICATOR

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SAFE OPERATION AND PROTECTION FEATURES

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POWER-SAVE MODE OPERATION, EFFICIENCY

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START-UP SEQUENCE

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NRESET INPUT: HARDWARE ENABLE / DISABLE

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SHUTDOWN

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SERIAL INTERFACE DESCRIPTION

OPERATION

The TPS6131x family is an integrated solution with a wide feature set for driving up to three LEDs for still-camera

flash and video-camera lighting applications. It employs a 2MHz fixed on-time, PWM current-mode converter to

generate the output voltage required to drive up to three high-power LEDs in parallel. The device integrates an

NMOS-switch power stage and a synchronous PMOS rectifier. The device also implements a set of linear low-

side current regulators to control the LED current when the battery voltage is higher than the diode forward

voltage.

The high efficiency boost converter stage and LED forward voltage adoption ensure lowest device input current

for a given LED output current.

A special circuit disconnects the load from the battery during shutdown of the converter. In conventional

synchronous-rectifier circuits, the back-gate diode of the high-side PMOS is forward biased in shutdown, allowing

current to flow from the battery to the output. The TPS6131x prevents this by disconnecting the cathode of the

back-gate diode of the high-side PMOS from the source when the regulator is in shutdown.

The TPS6131x device not only operates as a regulated current source, but also as a standard voltage-boost

regulator featuring a power-save mode for improved efficiency at light loads. If the input voltage is higher than

the programmed output voltage, a down mode is implemented that acts similarly to an LDO.

The power stage is capable of supplying a maximum total current of roughly 1500mA. The TPS6131x provides

three constant-current sinks, capable of sinking up to 2x 400mA (LED1 and LED3) and 800mA (LED2) in flash

mode.

Figure 37. TPS6131x States

Special effort is taken for safe operation and robust system integration. The battery voltage can be monitored so

that the flash current is not increased if the battery voltage drops by a programmable threshold. Internal timers

limit the flash on-time to prevent potential camera-engine software errors, and a video light watchdog acts in a

similar fashion. Multiple monitoring features (LED and die temperature, input voltage droop etc.) keep the device

and LEDs operating properly.

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