TPS60120, TPS60121, TPS60122, TPS60123, TPS60124, TPS60125

REGULATED 200-mA HIGH EFFICIENCY CHARGE PUMP

DC/DC CONVERTERS

SLVS257B – NOVEMBER 1999 – REVISED AUGUST 2000

21

POST OFFICE BOX 655303

APPLICATION INFORMATION

TPS6012x operated with ultralow quiescent current

Because the output of the TPS6012x is isolated from the input when the devices are disabled, and because the

internal resistive divider is disconnected in shutdown, an ultralow quiescent current mode can be implemented.

In this mode, the output voltage is sustained because the converter is periodically enabled to refresh the output

capacitor. The necessary external control signal that is applied to the ENABLE pin is generated from a

microcontroller like the ultralow power microcontroller MSP430. For a necessary supply current for the system

of 1 mA and a minimum supply voltage of 3 V with a 22-

µF output capacitor, the refresh has to be done after

a maximum of 3.5 ms. Longer refresh periods can be achieved with a larger output capacitor.

IN

IN

LBI

C1+

C1–

ENABLE

PGND GND

OUT

OUT

FB

LBO

C2+

C2–

C2

22

µF

Ci

10

µF

Output

3.3 V, 100 mA

C2

2.2

µF

C1

2.2

µF

R1

R2

Input

1.8 V to 3.6 V

ON

OFF

C3

1

µF

R4

1 M

Ω

R3

1 M

Ω

I

O

MCU

e.g.

MSP430

TPS60122

Figure 30. TPS60122 in UltraLow Quiescent Current Mode

regulated discharge of the output capacitors after disabling of the TPS6012x

During shutdown of the charge pump TPS6012x, the output is isolated from the input. Therefore, the discharging

of the output capacitor depends on the load and on the leakage current of the capacitor. In certain applications

it is necessary to completely remove the supply voltage from the load in shutdown mode. That means the output

capacitor of the charge pump has to be actively discharged when the charge pump is disabled. Figure 31 shows

one solution to this problem.

TPS601xx

OUT

IN

GND

ENABLE

+

CO

SN74AHC1G04

A

Y

VCC

GND

IN

ENABLE

GND

OUT

BSS138

Figure 31. Block Diagram of the Regulated Discharge of the Output Capacitor