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參數(shù)資料
| 型號(hào)： | FAN5631 |
| 廠商： | Fairchild Semiconductor Corporation |
| 英文描述： | Regulated Step-Down Charge Pump DC/DC Converter |
| 中文描述： | 穩(wěn)壓降壓電荷泵DC / DC轉(zhuǎn)換器 |
| 文件頁數(shù)： | 7/11頁 |
| 文件大?。?/td> | 569K |
| 代理商： | FAN5631 |
7
www.fairchildsemi.com
FAN5631/FAN5632 Rev. 1.0.0
F
Block Diagram
Figure 4. Block Diagram
Detailed Description
The FAN5631/FAN5632 switched capacitor DC/DC converter
automatically configures switches to achieve high efficiency and
provides a regulated output voltage by means of the Pulse Fre-
quency Modulation (PFM) pulse-skipping mode. An internal
soft-start circuit prevents excessive in-rush current drawn from
the supply. The switches are split into three segments. Based on
the values of V
IN
,
V
OUT
and I
OUT
, an internal circuitry deter-
mines the number of segments to be used to reduce current
spikes.
Step-Down Charge Pump Operation
When V
IN
≥
2
×
V
OUT
/0.9, a 2:1 configuration, as shown in Fig.
5, is enabled. The factor 0.9 is used instead of 1 in order to
account for the effect of resistive losses across the switches and
to accommodate hysteresis in the voltage detector comparator.
Two phase non-overlapping clock signals are generated to drive
four switches. When switches 1 and 3 are ON, switches 2 and 4
are OFF and C
B
is charged. When switches 2 and 4 are ON,
switches 1 and 3 are OFF and charge is transferred from C
B
to
C
OUT
.
When V
IN
< 2
×
V
OUT
/0.9, a 1:1 configuration, as shown in Fig. 6
is enabled. In the 1:1 configuration switch 3 is always OFF and
switch 4 is always ON. At the 1.6V output setting the configura-
tion changes from 2:1 to 1:1 at V
IN
= 3.56V. At the 1.3V output
setting the change occurs at V
IN
= 3.06V.
Pulse-Skipping PFM and Fractional Switch
Operation
When the regulated output voltage reaches its upper limit, the
switches are turned off and the output voltage reaches its lower
limit. Considering a step-down 2:1 mode of operation, 1.6V out-
put as an example, when the output reaches about 1.62V
(upper limit), the control logic turns off all switches. Switching
stops completely. This is pulse-skipping mode. Since the supply
is isolated from the output, the output voltage will drop. Once
the output drops to about 1.58V (lower limit), the device will
return to regular switching mode with one quarter of each switch
turning on first. Another quarter of each switch will be turned on
if V
OUT
cannot reach regulation by the time of the third charge
cycle. Full switch operation occurs only during startup or under
heavy load condition, when a half switch operation cannot
achieve regulation within seven charge cycles.
Soft-Star
t
The soft-start feature limits in-rush current when the device is ini-
tially powered up and enabled. The reference voltage is used to
UVLO
+
-
SHUTDOWN
CONTROL
LOGIC
CONFIGURATION
PULSE_SKIP
SHORT_CKT.
+
-
+
-
+
-
THERMAL
SHUTDOWN
IN
OUT
V
ref.
RAMP
FB
OUTPUT
150mV
1V
0.5* INPUT
VOLTAGE
REF.
SOFT START
V
ref.
RAMP
OSCILLATOR
(2MHz)
C+
C-
ENABLE
VIN
GND.
D
R
I
V
E
R
S
0.25SW1
0.25SW1
0.25SW4
0.25SW4 0.5SW4
0.25SW3
0.25SW3 0.5SW3
0.5SW2
0.25SW2
0.25SW2
0.5SW1
FB
V
OUT
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| FAN5631_07 | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:Regulated Step-Down Charge Pump DC/DC Converter |
| FAN5631_AAB3086B WAF | 制造商:Fairchild Semiconductor Corporation 功能描述: |
| FAN5631MPX | 功能描述:電荷泵 SYSTEM_POWER RoHS:否 制造商:Maxim Integrated 功能:Inverting, Step Up 輸出電壓:- 1.5 V to - 5.5 V, 3 V to 11 V 輸出電流:100 mA 電源電流:1 mA 最大工作溫度:+ 70 C 封裝 / 箱體:SOIC-8 Narrow 封裝:Tube |
| FAN5632 | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:Regulated Step-Down Charge Pump DC/DC Converter |
| FAN5632MPX | 功能描述:電荷泵 SYSTEM_POWER RoHS:否 制造商:Maxim Integrated 功能:Inverting, Step Up 輸出電壓:- 1.5 V to - 5.5 V, 3 V to 11 V 輸出電流:100 mA 電源電流:1 mA 最大工作溫度:+ 70 C 封裝 / 箱體:SOIC-8 Narrow 封裝:Tube |
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