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參數(shù)資料
| 型號： | ICL7662 |
| 廠商： | Intersil Corporation |
| 英文描述： | CMOS Voltage Converters(CMOS電壓變換器) |
| 中文描述： | CMOS、電壓變換器 |
| 文件頁數(shù)： | 7/10頁 |
| 文件大?。?/td> | 88K |
| 代理商： | ICL7662 |
3-51
Theoretical Power Efficiency
Considerations
In theory a voltage multiplier can approach 100% efficiency if
certain conditions are met:
1. The drive circuitry consumes minimal power.
2. The output switches have extremely low ON resistance
and virtually no offset.
3. Theimpedancesofthepumpandreservoircapacitorsare
negligible at the pump frequency.
The ICL7662 approaches these conditions for negative
voltage multiplication if large values of C
1
and C
2
are used.
ENERGY IS LOST ONLY IN THE TRANSFER OF CHARGE
BETWEEN CAPACITORS IF A CHANGE IN VOLTAGE
OCCURS.
The energy lost is defined by:
E = 1/2C
1
(V
12
- V
22
)
where V
1
and V
2
are the voltages on C
1
during the pump
and transfer cycles. If the impedances of C
1
and C
2
are
relatively high at the pump frequency (refer to Figure 15)
compared to the value of R
L
, there will be a substantial
difference in the voltages V
1
and V
2
. Therefore it is not only
desirable to make C
2
as large as possible to eliminate output
voltage ripple, but also to employ a correspondingly large
value for C
1
in order to achieve maximum efficiency of
operation.
Do’s and Don’ts
1. Do not exceed maximum supply voltages.
2. DonotconnectLVterminaltoGROUNDforsupplyvoltag-
es greater than 10V.
3. When using polarized capacitors, the + terminal of C
1
must be connected to pin 2 of the ICL7662 and the + ter-
minal of C
2
must be connected to GROUND.
4. If the voltage supply driving the 7662 has a large source
impedance (25
- 30
), then a 2.2
μ
F capacitor from pin
8 to ground may be required to limit rate of rise of input
voltage to less than 2V/
μ
s.
5. User should insure that the output (pin 5) does not go
more positive than GND (pin 3). Device latch up will occur
under these conditions.
A 1N914 or similar diode placed in parallel with C
2
will
prevent the device from latching up under these conditions.
(Anode pin 5, Cathode pin 3).
Typical Applications
Simple Negative Voltage Converter
The majority of applications will undoubtedly utilize the
ICL7662 for generation of negative supply voltages. Figure
16 shows typical connections to provide a negative supply
where a positive supply of +4.5V to 20.0V is available. Keep
in mind that pin 6 (LV) is tied to the supply negative (GND)
for supply voltages below 10V.
The output characteristics of the circuit in Figure 16A can be
approximated by an ideal voltage source in series with a
resistance as shown in Figure 16B. The voltage source has
a value of -(V+). The output impedance (R
O
) is a function of
the ON resistance of the internal MOS switches (shown in
Figure 2), the switching frequency, the value of C
1
and C
2
,
and the ESR (equivalent series resistance) of C
1
and C
2
. A
good first order approximation for R
O
is:
Combining the four R
SWX
terms as R
SW
, we see that
R
SW
, the total switch resistance, is a function of supply
voltage and temperature (See the Output Source Resistance
graphs), typically 24
at +25
o
C and 15V, and 53
at +25
o
C
and 5V. Careful selection of C
1
and C
2
will reduce the
remaining terms, minimizing the output impedance. High
value capacitors will reduce the 1/(f
PUMP
x C
1
) component,
and low FSR capacitors will lower the ESR term. Increasing
the oscillator frequency will reduce the 1/(f
PUMP
x C
1
) term,
but may have the side effect of a net increase in output
impedance when C
1
> 10
μ
F and there is no longer enough
time to fully charge the capacitors every cycle. In a typical
application where f
OSC
= 10kHz and C = C
1
= C
2
= 10
μ
F:
Since the ESRs of the capacitors are reflected in the output
impedance multiplied by a factor of 5, a high value could
potentially swamp out a low 1/(f
PUMP
x C
1
) term, rendering
an increase in switching frequency or filter capacitance
ineffective. Typical electrolytic capacitors may have ESRs as
high as 10
.
V
OUT
= -V
IN
C
2
V
IN
C
1
S
3
S
4
S
1
S
2
8
2
4
5
3
3
7
FIGURE 15. IDEALIZED NEGATIVE CONVERTER
R
O
2(R
SW1
+ R
SW3
+ ESRC
1
)
+ 2(R
SW2
+ R
SW4
+ ESRC
1
) +
1
+ ESRC
2
f
PUMP
x C
1
(f
PUMP
=
f
OSC
,
2
R
SWX
= MOSFET switch resistance)
R
O
2 x R
SW
+
1
+ 4 x ESRC
1
+ ESRC
2
f
PUMP
x C
1
R
O
2 x 23 +
1
+ 4 ESRC
1
+ ESRC
2
(5 x 10
3
x 10 x 10
-6
)
R
O
46 + 20 + 5 x ESR
C
ICL7662
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| ICL7662 WAF | 制造商:Harris Corporation 功能描述: |
| ICL7662CBA | 功能描述:電荷泵 CMOS Voltage Converter 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 |
| ICL7662CBA+ | 功能描述:電荷泵 CMOS Voltage Converter 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 |
| ICL7662CBA+T | 功能描述:電荷泵 CMOS Voltage Converter 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 |
| ICL7662CBA-T | 功能描述:電荷泵 CMOS Voltage Converter 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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