Datasheet

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 • DALLAS, TEXAS 75265
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
C
i
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 MΩ
R3
1 MΩ
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
+
C
O
SN74AHC1G04
A
Y
VCC
GND
IN
ENABLE
GND
OUT
BSS138
Figure 31. Block Diagram of the Regulated Discharge of the Output Capacitor