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TPS60110 View Datasheet(PDF) - Texas Instruments

Part NameDescriptionManufacturer
TPS60110 REGULATED 5-V 300-mA LOW-NOISE CHARGE PUMP DC/DC CONVERTER TI
Texas Instruments TI
TPS60110 Datasheet PDF : 26 Pages
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TPS60110
REGULATED 5ĆV 300ĆmA LOWĆNOISE
CHARGE PUMP DC/DC CONVERTER
SLVS215C − JUNE 1999 − REVISED AUGUST 2008
detailed description (continued)
start-up procedure
During start-up, i.e. when ENABLE is set from logic low to logic high, the switches T12 and T14 (charge pump
1), and the switches T22 and T24 (charge pump 2) are conducting to charge up the output capacitor until the
output voltage VO reaches 0.8×VIN. When the start-up comparator detects this limit, the IC begins to operate
in the mode selected with SKIP and COM. This start-up charging of the output capacitor specifies a short start-up
time and eliminates the need for a Schottky diode between IN and OUT.
pulse-skip mode
In pulse-skip mode (SKIP = high), the error amplifier disables switching of the power stages when it detects an
output higher than 5 V. The oscillator halts. The IC then skips switching cycles until the output voltage drops
below 5 V. Then the error amplifier reactivates the oscillator and switching of the power stages starts again. The
pulse-skip regulation mode minimizes operating current because it does not switch continuously and
deactivates all functions except bandgap reference and error amplifier when the output is higher than 5 V. When
switching is disabled from the error amplifier, the load is also isolated from the input. SKIP is a logic input and
should not remain floating. The typical operating circuit of the TPS60110 in pulse skip mode is shown in
Figure 1.
constant-frequency mode
When SKIP is low, the charge pump runs continuously at the frequency fOSC. The control circuit, fed from the
error amplifier, controls the charge on C1F and C2F by driving the gates of the FETs T12/T13 and T22/T23,
respectively. When the output voltage falls, the gate drive increases, resulting in a larger voltage across C1F
and C2F. This regulation scheme minimizes output ripple. Since the device switches continuously, the output
noise contains well-defined frequency components, and the circuit requires smaller external capacitors for a
given output ripple. However, constant-frequency mode, due to higher operating current, is less efficient at light
loads than pulse-skip mode.
INPUT
2.7 V to 5.4 V
CIN
15 µF
+
C1F
2.2 µF
OFF/ON
SKIP COM CLK
IN
OUT
IN
OUT
TPS60110 FB
C1+
C2+
C1−
C2−
ENABLE SYNC
PGND GND
C2F
2.2 µF
OUTPUT
5 V 300 mA
+
CO = 33 µF
Figure 24. Typical Operating Circuit TPS60110 in Constant Frequency Mode
Table 1. Tradeoffs Between Operating Modes
FEATURE
PULSE-SKIP MODE
(SKIP = High)
CONSTANT-FREQUENCY MODE
(SKIP = Low)
Best light-load efficiency
X
Smallest external component size for a given output ripple
X
Output ripple amplitude
Small amplitude
Very small amplitude
Output ripple frequency
Variable
Constant
Load regulation
Very good
Good
NOTE: Even in pulse-skip mode the output ripple amplitude is small if the push-pull operating mode is selected via COM.
POST OFFICE BOX 655303 DALLAS, TEXAS 75265
11
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