TPS60500, TPS60501

TPS60502, TPS60503

SLVS391B – OCTOBER 2001 – REVISED FEBRUARY 2002

10

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PRINCIPLES OF OPERATION

The TPS6050x devices use fractional conversion to achieve high efficiency over a wide input and output voltage

range. Depending on the input to output voltage ratio and output current, internal circuitry switches between an

LDO mode, a 2/3x mode, a 0.5x mode, and a 1/3x mode.

LDO conversion mode

In the LDO mode, the flying capacitors are no longer used for transferring energy. The switches 1, 2, 5, and 6

are closed and connect the input directly with the output. This mode is automatically selected if the input to output

voltage ratio does not allow the use of another conversion mode with higher efficiency. In LDO mode, the

regulation is done by switching off MOSFET 2 and 6 until the output current reaches the linear-skip current (150

mA typ). At a higher output current, the output voltage is regulated by controlling the resistance of the switch.

The minimum input to output voltage difference required for regulation is 1 V.

C1F

C2F

SW1

SW2

SW3

SW4

SW9

SW5

SW6

SW7

SW8

++

+

VIN

OUT

Co

Figure 22.

LDO Conversion Mode

2/3x conversion mode

In the first cycle, the two flying capacitors are connected in parallel and are charged up in series with the output

capacitor. In the second cycle, the flying capacitors are connected in series. This mode provides higher

efficiency than the LDO mode because the current into VIN is only 2/3 of the output current. The mode is

automatically selected if the input voltage is higher than 3/2 of the selected output voltage.

C1F

C2F

SW1

SW2

SW3

SW4

SW9

SW5

SW6

SW7

SW8

++

+

VIN

OUT

Co

SW1

SW2

SW3

SW4

SW9

SW5

SW6

SW7

SW8

++

+

VIN

OUT

Co

C1F

C2F

Phase 1: Charging of Flying Caps

Phase 2: Discharging of Flying Caps

Figure 23.

2/3x Conversion Mode