(

)

Vout

Vref

R8

R7

R8

tol

= tol

+

tol

+ tol

R8+R7

æ

ö ´

ç

÷

è

ø

R8

Vout = Vref 1 +

(Volts)

R7

æ

ö

ç

÷

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TPS55332-Q1

www.ti.com

SLVS939B – JUNE 2009 – REVISED DECEMBER 2014

7.3 Feature Description

The TPS55332 is a step up (boost) dc/dc converter using voltage-control mode scheme. The following sections

include descriptions of the individual pin functions.

7.3.1 Input Voltage (VIN)

The VIN pin is the input power source for the TPS55332. This pin must be externally protected against voltage

level transients greater than 60 V and reverse battery. In boost mode the input current drawn from this pin is

pulsed, with fast rise and fall times. Therefore, this input line requires a filter capacitor to minimize noise.

Additionally, for EMI considerations, an input filter inductor may also be required.

7.3.2 Output Voltage (Vout)

The output voltage, Vout, is generated by the converter supplied from the battery voltage VIN and external

components (L, C). The output is sensed through an external resistor divider and compared with an internal

reference voltage.

The value of the adjustable output voltage in boost mode is selectable between VIN × 1.05 to 50 V if the

to the following relationship:

(1)

Where:

R7 and R8 are feedback resistors

Vref = 2.5 V (typ)

The internal reference voltage Vref has a ±1.5% tolerance. The overall output voltage tolerance is dependent on

the external feedback resistors. To determine the overall output voltage tolerance, use the following relationship:

(2)

Typically, an output capacitor within the range of 10

μF to 400 μF is used. This terminal has a filter capacitor with

low ESR characteristics in order to minimize output ripple voltage.

when Vout > Vsupply.

7.3.4 Over-Current Protection (SW)

Over-current protection is implemented by sensing the current through the NMOS switch FET. The sensed

current is then compared to a current reference level representing the over-current threshold limit. If the sensed

current exceeds the over-current threshold limit, the over-current indicator is set true. The system ignores the

over-current indicator for the leading edge blanking time at the beginning of each cycle to avoid any turn-on

noise glitches.

Once the over-current indicator is set true, over-current protection is triggered. The MOSFET is turned off for the

rest of the cycle after a propagation delay. The over-current protection scheme is called cycle-by-cycle current

limiting. If the sensed current continues to increase during cycle-by-cycle current limiting, the temperature of the

device starts to rise, and the TSD kicks in and shuts down switching until the device cools down.

7.3.5 Oscillator Frequency (RT)

can be set in the range of 80 kHz to 2.2 MHz. In addition, the switching frequency can be imposed externally by

switching frequency determined by the RT pin, and the internal oscillator is clocked by the external

synchronization clock input.

Copyright © 2009–2014, Texas Instruments Incorporated

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Product Folder Links: TPS55332-Q1