TPS61301 datasheet(49/77 Pages) TI

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OutputVoltage, VOUT

PowerGood, PG

VBAT

LEDFlashCurrent, IFLASH

OV[3:0]

0000

0001

0010

0011

0100

0101

~200 ms

FeedbackSenseComparatorOutput

VLED > 400 mV

Self-Calibration,

SELFCAL bit (write)

Self-Calibration,

SELFCAL bit (read)

ESRxILED

~200 ms

FeedbackSense

ComparatorInformation

TPS61300

TPS61301

TPS61305, TPS61305A

www.ti.com

SLVS957D – JUNE 2009 – REVISED OCTOBER 2012

STORAGE CAPACITOR, PRE-CHARGE VOLTAGE CALIBRATION

High-power LEDs tend to exhibit a wide forward voltage distribution. The TPS6130x device integrates a self-

calibration procedure that can be used to determine the optimum super-capacitor pre-charge voltage based on

the actual worst case LED forward voltage and ESR of the storage capacitor. This calibration procedure is meant

to start-off at a min. output voltage and can be initiated by setting the SELFCAL bit (preferably with

MODE_CTRL[1:0] = 00, ENVM = 0, ENDCL = 0).

The calibration procedure monitors the sense voltage across the low-side current regulators (according to

ENLED[3:1] bits setting) and registers the worst case LED (i.e. the LED featuring the largest forward voltage).

The TPS6130x device automatically sweeps through its output voltage range and performs a short duration flash

strobe for each step (refer to FC13[1:0] and FC2[2:0] bits settings).

In direct drive mode (HC_SEL = L), the energy is being directly transferred from the battery to the LEDs. In high-

current mode (HC_SEL = H), the energy is supplied exclusively by the output reservoir capacitor and the

inductive power stage is turned-off for the flash strobe period of time.

The sequence is stopped as soon as the device detects that each of the low-side current regulators have enough

headroom voltage (i.e. 400mV typ.). The device returns the according output voltage in the register OV[3:0] and

sets the SELFCAL bit. This bit is only being reset at the (re-)start of a calibration cycle. In other words, when

SELFCAL is asserted the output voltage register (OV[3:0]) returns the result of the last calibration sequence.

Figure 74. LED Forward Voltage Self-Calibration Principle

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Product Folder Links: TPS61300 TPS61301 TPS61305 TPS61305A

TPS61301 Datasheet(PDF) 49 Page - Texas Instruments

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