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參數(shù)資料
| 型號： | SP784 |
| 英文描述： | Programmable Charge Pump |
| 中文描述： | 可編程電荷泵 |
| 文件頁數(shù)： | 10/16頁 |
| 文件大小： | 224K |
| 代理商： | SP784 |
10
SP782/SP784 DS/08
SP782/784 Programmable Charge Pump
Copyright 2000 Sipex Corporation
Figure 4. Charge Pump Phase 2 for
±
10V.
The oscillator frequency or clock rate for
the charge pump is designed for low power
operation. The oscillator changes from a high
frequency mode (400kHz) to a low frequency
mode (20kHz) when the SD pin goes to a logic
"1". The lower frequency allows the
SP782/
SP784
to conserve power when the outputs are
not being used.
EFFICIENCY INFORMATION
A charge pump theoretically produces a doubled
voltage at 100% efficiency. However in the real
world, there is a small voltage drop on the output
which reduces the output efficiency. The
SP782
and
SP784
can usually run 99.9% efficient with-
out driving a load. While driving a 1k
load, the
SP782
and
SP784
remain at least 90% efficient.
Total Output Voltage Efficiency =
[(V
OUT
+) / (2*V
CC
)] + [(V
OUT
–) / (–2*V
CC
)] ;
V
OUT
+ = 2*V
CC
+ V
DROP
+
V
OUT
– = –2*V
CC
+ V
DROP
–
V
DROP
– = (I–)*(R
OUT
–)
V
DROP
+ = (I+)*(R
OUT
+)
Power Loss = I
OUT
*(V
DROP
)
The efficiency changes as the external charge
pump capacitors are varied. Larger capacitor
values will strengthen the output and reduce
output ripple usually found in all charge pumps.
Although smaller capacitors will cost less and
Figure 6. Charge Pump Phase 3.
V
CC
= +5V
–10V
V
DD
Storage Capacitor
C
1
C
2
C
4
+
+
+
–
–
–
V
SS
Storage Capacitor
C
3
+
–
V
CC
= +5V
–5V
–5V
+5V
V
DD
Storage Capacitor
C
1
C
2
C
4
+
+
+
–
–
–
V
SS
Storage Capacitor
C
3
+
–
Figure 7. Charge Pump Phase 4.
Figure 5. Charge Pump Phase 2 for
±
5V.
V
CC
= +5V
V
DD
Storage Capacitor
C
1
C
2
C
4
+
+
+
–
–
–
V
SS
Storage Capacitor
C
3
+
–
–5V
V
CC
= +5V
+10V
V
DD
Storage Capacitor
C
1
C
2
C
4
+
+
+
–
–
–
V
SS
Storage Capacitor
C
3
+
–
save board space, lower values will reduce the
output drive capability.
The output voltage ripple is also affected by the
capacitors, specifically C3 and C4. Larger val-
ues will reduce the output ripple for a given load
of current. The current drawn from either output
is supplied by just the storage capacitor, C3 or
C4, during one half cycle of the internal oscilla-
tor. Note that the output current from the postive
charge pump is the load current plus the current
taken by the negative charge pump. Thus the
formula representation for the output ripple
voltage is:
V
RIPPLE
+ = {1 / (f
OSC
) * 1 / C3} * 0.5 * I
OUT
+
V
RIPPLE
– = {1 / (f
OSC
) * 1 / C3} * 0.5 * I
OUT
–
To minimize the output ripple, the C3 and C4
storage capacitors can be increased to over 10
μ
F
whereas the pump capacitors can range from
1
μ
F to 5
μ
F.
Multiple
SP782/784
charge pumps can be
connected in parallel. However, the output
resistance on both pump outputs will be
reduced. The effective output resistance is the
output resistance of one pump divided by the
number of charge pumps connected. It is
important to keep the C1 and C2 capacitors
separate for each charge pump. The storage
capacitors, C3 and C4, can be shared.
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相關代理商/技術參數(shù) |
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|---|---|
| SP784CP | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:Programmable Charge Pump |
| SP784CT | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:Programmable Charge Pump |
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| SP78K0S | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Two Great Forces in the 8-bit Realm Pamphlet | Pamphlet[09/2002] |
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