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Soft Start

95%

EN

5%

V

OUT

t

Start

t

RAMP

100% Duty Cycle Low Dropout Operation

V (min)=

I

V (max)+I (max)x(r

(max)+R )

O

O

DS(on)

L

(3)

Undervoltage Lockout

Mode Selection

TPS65050, TPS65051, TPS65052

TPS65054, TPS65056

SLVS710 – JANUARY 2007

The two converters have an internal soft start circuit that limits the inrush current during start-up. During soft

start, the output voltage ramp up is controlled as shown in Figure 20.

Figure 20. Soft Start

The converters offer a low input to output voltage difference while still maintaining operation with the use of the

100% duty cycle mode. In this mode, the P-channel switch is constantly turned on. This is useful in

battery-powered applications to achieve longest operation time by taking full advantage of the whole battery

voltage range. (i.e. The minimum input voltage to maintain regulation depends on the load current and output

voltage) and can be calculated as:

with:

• I

• r

• R

• V

The undervoltage lockout circuit prevents the device from malfunctioning at low input voltages and from

excessive discharge of the battery and disables all internal circuitry. The undervoltage lockout threshold, sensed

The MODE pin allows mode selection between forced PWM Mode and power Safe Mode for both converters.

Connecting this pin to GND enables the automatic PWM and power save mode operation. The converters

operates in fixed frequency PWM mode at moderate to heavy loads and in the PFM mode during light loads,

maintaining high efficiency over a wide load current range.

21

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