Datasheet

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   
   
SLVS216B − JUNE 1999 − JUNE 2008
10
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
detailed description
operating principle
The TPS60111 charge pump provides a regulated 5-V output from a 2.7-V to 5.4-V input. It delivers a maximum
load current of 150 mA. Designed specifically for space critical battery powered applications, the complete
charge pump circuit requires only four external capacitors. The circuit can be optimized for highest efficiency
at light loads or lowest output noise. The TPS60111 consists of an oscillator, a 1.22-V bandgap reference, an
internal resistive feedback circuit, an error amplifier, high current MOSFET switches, a shutdown/start-up
circuit, and a control circuit (Figure 25).
C1+
C1−
ENABLE
OUT
FB
0°
180°
PGND
C
1F
IN
CHARGE PUMP 2
C2+
C2−
OUT
PGND
C
2F
IN
T
22
T
21
OSCILLATOR
GND
SKIP
COM
CLK
V
REF
−
+
−
+
CONTROL
CIRCUIT
0.8 × V
IN
−
+
−
+
SHUTDOWN/
START-UP
CONTROL
SYNC
T
11
T
12
T
13
T
14
T
24
T
23
CHARGE PUMP 1
Figure 25. Functional Block Diagram TPS60111
The oscillator runs at a 50% duty cycle. The device consists of two single-ended charge pumps which operate
with 180° phase shift. Each single ended charge pump transfers charge into its transfer capacitor (C
xF
) in one
half of the period. During the other half of the period (transfer phase), C
xF
is placed in series with the input to
transfer its charge to C
O
. While one single-ended charge pump is in the charge phase, the other one is in the
transfer phase. This operation guarantees an almost constant output current which ensures a low output ripple.
If the clock were to run continuously, this process would eventually generate an output voltage equal to two times
the input voltage (hence the name doubler). In order to provide a regulated fixed output voltage of 5 V, the
TPS60111 uses either pulse-skip mode or constant-frequency mode. Pulse-skip mode and constant-frequency
mode are externally selected via the SKIP input pin.