参数资料
| 型号： | ICL7660SIPA |
| 厂商： | Intersil |
| 文件页数： | 9/13页 |
| 文件大小： | 0K |
| 描述： | IC REG SWITCHED CAP DBL INV 8DIP |
| 标准包装： | 1,000 |
| 类型： | 切换式电容器（充电泵），倍增器，反相 |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | -1.5 V ~ -12 V，±3 V ~ ±24 V |
| 输入电压： | 1.5 V ~ 12 V |
| 频率 - 开关： | 10kHz，35kHz |
| 电流 - 输出： | 45mA |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 通孔 |
| 封装/外壳： | 8-DIP（0.300"，7.62mm） |
| 包装： | 管件 |
| 供应商设备封装： | 8-PDIP |
ICL7660S, ICL7660A
Typical Applications
Simple Negative Voltage Converter
charge the capacitors every cycle. Equation 4 shows a typical
application where f OSC = 10kHz and C = C 1 = C 2 = 10μF:
R 0 ? 2x23 + --------------------------------------------------- + 4xESR C1 + ESR C2
5 × 10 × 10 × 10
The majority of applications will undoubtedly utilize the
ICL7660S and ICL7660A for generation of negative supply
voltages. Figure 15 shows typical connections to provide a
negative supply where a positive supply of +1.5V to +12V is
1
3 – 6
R 0 ? 46 + 20 + 5 × ESR C
(EQ. 4)
available. Keep in mind that pin 6 (LV) is tied to the supply
negative (GND) for supply voltage below 3.5V.
V+
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
10μF
+
-
1
2
3
4
ICL7660S
ICL7660A
8
7
6
5
-
R O
V OUT
ineffective. Typical electrolytic capacitors may have ESRs as
high as 10 Ω .
Output Ripple
ESR also affects the ripple voltage seen at the output. The
peak-to-peak output ripple voltage is given by Equation 5:
V RIPPLE ? ? ----------------------------------------- + 2ESR C2 × I OUT ?
PUMP × C 2
-
10μF +
V OUT = -V+
V+
+
? 2 × f ?
1
(EQ. 5)
15A.
15B.
A low ESR capacitor will result in a higher performance
FIGURE 15. SIMPLE NEGATIVE CONVERTER AND ITS
OUTPUT EQUIVALENT
The output characteristics of the circuit in Figure 15 can be
approximated by an ideal voltage source in series with a
resistance as shown in Figure 15B. 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
output.
Paralleling Devices
Any number of ICL7660S and ICL7660A voltage converters
may be paralleled to reduce output resistance. The reservoir
capacitor, C 2 , serves all devices, while each device requires
its own pump capacitor, C 1 . The resultant output resistance
is approximated in Equation 6:
Figure 14), 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 shown in
Equation 2:
R OUT ( of ICL7660S )
n ( number of devices )
R OUT = ---------------------------------------------------------
Cascading Devices
(EQ. 6)
R 0 ? 2 ( ( R SW1 + R SW3 + ESR C1 ) + 2 ( R SW2 + R SW4 + ESR C1 ) )
The ICL7660S and ICL7660A may be cascaded as shown to
-------------------------------- + ESR C2
1
f PUMP × C 1
(EQ. 2)
produce larger negative multiplication of the initial supply
voltage. However, due to the finite efficiency of each device,
the practical limit is 10 devices for light loads. The output
2
f OSC
f PUMP = --------------
( R SWX = MOSFET Switch Resistance )
voltage is defined as shown in Equation 7:
V OUT = – n ( V IN )
(EQ. 7)
R 0 ? 2xR SW + -------------------------------- + 4xESR C1 + ESR C2
Combining the four R SWX terms as R SW , we see in
Equation 3 that:
1
f PUMP × C 1
(EQ. 3)
where n is an integer representing the number of devices
cascaded. The resulting output resistance would be
approximately the weighted sum of the individual ICL7660S
and ICL7660A R OUT values.
R SW , the total switch resistance, is a function of supply
voltage and temperature (see the output source resistance
graphs, Figures 2, 3, and 11), typically 23 Ω at +25°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
ESR 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 > 10μF and is not long enough to fully
9
Changing the ICL7660S and ICL7660A Oscillator
Frequency
It may be desirable in some applications, due to noise or other
considerations, to alter the oscillator frequency. This can be
achieved simply by one of several methods.
By connecting the Boost Pin (Pin 1) to V+, the oscillator
charge and discharge current is increased and, hence, the
oscillator frequency is increased by approximately 3.5 times.
The result is a decrease in the output impedance and ripple.
FN3179.7
January 23, 2013
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