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V

-OutputVoltage-V

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VBAT=1.2V

VBAT=1.8V

VBAT=2.4V

VBAT=3.6V

VBAT=5V

Power-Save Mode

TPS61070, TPS61071

TPS61072, TPS61073

SLVS510A – JULY 2006 – REVISED JANUARY 2007

DETAILED DESCRIPTION (continued)

Figure 22. Precharge and Short Circuit Current

After charging the output capacitor to the input voltage, the device starts switching. If the input voltage is below

1.8 V, the device works with a fixed duty cycle of 70% until the output voltage reaches 1.8 V. After that the duty

cycle is set depending on the input output voltage ratio. Until the output voltage reaches its nominal value, the

boost switch current limit is set to 50% of its nominal value to avoid high peak currents at the battery during

start-up. As soon as the output voltage is reached, the regulator takes control, and the switch current limit is set

back to 100%.

inductor current becomes zero, they automatically enter the power-save mode to improve efficiency. In the

power-save mode, the converters only operate when the output voltage trips below a set threshold voltage. It

ramps up the output voltage with one or several pulses and returns to the power-save mode once the output

voltage exceeds the set threshold voltage. If output power demand increases and the inductor current no longer

goes below zero, the device again enters the fixed PWM mode. In this mode, there is no difference between the

PWM only versions TPS61071 and TPS61072 and the power-save mode enabled versions TPS61070 and

TPS61073.

(1)

TPS61073 is in the prodcut preview stage of development.

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