MAX

OUT

FLED_MAX

V

= V

Number +1V

´

1

MAX

OUT

V

+1V

R2 =

R3

2.95V

æ

ö

-

´

ç

÷

è

ø

TPS61199

www.ti.com

SLVSAN3 A

– DECEMBER 2010 – REVISED MAY 2011

removes this IFB pin from the output voltage regulation loop. Current regulation of the remaining IFB pins is

not affected.

If the voltage on all the IFB pins exceed the threshold, the IC repeatedly attempts to restart until the fault is

cleared.

4. IFB over-voltage protection

damage. The IC will re-start when IFB pin voltage falls below the threshold. The time delay depends on how

quickly IFB voltage can fall. It is usually determined by the amount of output capacitance and load.

5. Output over-voltage protection using the OVP pin:

Use a resistor divider to program the clamp threshold voltage as follows:

number (n) of series LEDs. Add 1V to account for regulation and resistor tolerances and load transients.

(3)

(b) The recommended bottom feedback resistor (R3, in the ) at 10k. Calculate the top resistor (R2, in the

Figure 1) using the following equation

(4)

When the IC detects that the OVP pin exceeds 2.95V, indicating that the output voltage has exceeded the

clamp threshold voltage, the IC clamps the output voltage to the set threshold.

When the OVP pin voltage is higher than 3.0V, indicating that the output is higher than the clamp threshold

voltage due to transients or high voltage noise spike coupling from external circuits, the IC shuts down the

boost controller until the output drops below the clamp threshold voltage.

6. Output short to ground protection

When the inductor peak current reaches twice the switch current limit in each switch cycle, the IC

immediately disables the boost controller until the fault is cleared. This protects the IC and external

components from damage if the output is shorted to ground.

7. Thermal Protection

When the IC junction temperature is over 150

°C, the thermal protection circuit is triggered and shuts down

the device immediately. The device automatically restarts when the junction temperature falls back to less

than 150

°C, with approximate 15°C hysteresis.

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© 2010–2011, Texas Instruments Incorporated

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