Datasheet


   
   
SLVS216B − JUNE 1999 − JUNE 2008
12
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
detailed description (continued)
push-pull operating mode
In push-pull operating mode (COM = low), the two single-ended charge pumps operate with 180° phase shift.
The oscillator signal has a 50% duty cycle. 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. COM is a logic input and should not remain floating. The typical operating circuit
of the TPS60111 in push-pull mode is shown in Figure 1 and Figure 26.
single-ended operating mode
When COM is high, the device runs in single-ended operating mode. The two single-ended charge pumps
operate in parallel without phase shift. They transfer charge into the transfer capacitor (C
F
) in one half of the
period. During the other half of the period (transfer phase), C
F
is placed in series with the input to transfer its
charge to C
O
. In single-ended operating mode only one transfer capacitor (C
F
= C
1F
+ C
2F
) is required, resulting
in less board space.
IN
IN
C1+
C1−
ENABLE
OUT
OUT
FB
C2+
C2−
SYNC
SKIP COM CLK
PGND GND
INPUT
2.7 V to 5.4 V
C
IN
4.7 µF
OUTPUT
5 V 150 mA
C
O
= 15 µF
C
F
= 2.2 µF
+
OFF/ON
TPS60111
+
Figure 27. Typical Operating Circuit TPS60111 in Single-Ended Operating Mode
Table 2. Tradeoffs Between Operating Modes
FEATURE PUSH-PULL MODE
(COM = Low)
SINGLE-ENDED MODE
(COM = High)
Output ripple amplitude Small amplitude Large amplitude
Smallest board space X