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參數(shù)資料
| 型號(hào)： | NCP7662 |
| 廠商： | ON SEMICONDUCTOR |
| 英文描述： | INDUCTORLESS VOLTAGE CONVERTER |
| 中文描述： | 電感電壓轉(zhuǎn)換器 |
| 文件頁(yè)數(shù)： | 5/12頁(yè) |
| 文件大?。?/td> | 152K |
| 代理商： | NCP7662 |
NCP7662
http://onsemi.com
5
TYPICAL APPLICATIONS
Simple Negative Voltage Converter
The majority of applications will undoubtedly utilize the
NCP7662 for generation of negative supply voltages.
Figure 3 shows typical connections to provide a negative
supply where a positive supply of +1.5 V to +15 V is
available. Keep in mind that pin 6 (LV) is tied to the supply
negative (GND) for supply voltages below 3.5 volts.
Figure 3. Simple Negative Converter
and its Output Equivalent
10
μ
F
10
μ
F
4
1
2
3
8
7
6
5
N
+
VOUT
RO
V+
+
–
–
= –V+
V+
+
–
VOUT
(a)
(b)
The output characteristics of the circuit in Figure 3 can be
approximated by an ideal voltage source in series with a
resistance as shown in Figure 3b. The voltage source has a
value of –(V+). The output impedance (RO) is a function of
the ON resistance of the internal MOS switches (shown in
Figure 2), the switching frequency, the value of C1 and C2,
and the ESR (equivalent series resistance) of C1 and C2. A
good first order approximation for RO is:
RO
ESRC1)
fPUMP
fOSC
2
Combining the four RSWX terms as RSW, we see that:
2(RSW1
RSW3
ESRC1)
1
2(RSW2
ESRC2
RSW4
C1
(fPUMP
, RSWX
MOSFET switch resistance)
RO
2
RSW
1
fPUMP
C1
4
ESRC1
ESRC2
RSW, the total switch resistance, is a function of supply
voltage and temperature (see the Output Source Resistance
graphs), typically 23
at +25
°
C and 5 V. Careful selection
of C1 and C2 will reduce the remaining terms, minimizing
the output impedance. High value capacitors will reduce the
1/(fPUMP
C1) component, and low ESR capacitors will
lower the ESR term. Increasing the oscillator frequency will
reduce the 1/(fPUMP
C1) term, but may have the side
effect of a net increase in output impedance when C1
10
μ
F and there is not enough time to fully charge the
capacitors every cycle. In a typical application when fOSC =
10 kHz and C = C1 = C2 = 10
μ
F:
RO
2
23
1
10
5
103
10–6)
4
ESRC1
ESRC2
RO
(46
20
5
ESRC)
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/(fPUMP
rendering an increase in switching frequency or filter
capacitance ineffective. Typical electrolytic capacitors may
have ESRs as high as 10
.
C1) term,
Output Ripple
ESR also affects the ripple voltage seen at the output. The
total ripple is determined by 2 voltages, A and B, as shown
in Figure 4. Segment A is the voltage drop across the ESR
of C2 at the instant it goes from being charged by C1 (current
flowing into C2) to being discharged through the load
(current flowing out of C2). The magnitude of this current
change is 2
IOUT, hence the total drop is 2
ESRC2 volts. Segment B is the voltage change across C2
during time t2, the half of the cycle when C2 supplies current
to the load. The drop at B is IOUT
peak–to–peak ripple voltage is the sum of these voltage
drops:
IOUT
t2/C2 volts. The
VRIPPLE
1
2
fPUMP
C2
ESRC2
IOUT
Figure 4. Output Ripple
0
–(V+)
B
A
t2
t1
V
Paralleling Devices
Any number of NCP7662 voltage converters may be
paralleled to reduce output resistance (Figure 5). The
reservoir capacitor, C2, serves all devices, while each device
requires its own pump capacitor, C1. The resultant output
resistance would be approximately:
ROUT
ROUT(of NCP7662)
n (number of devices)
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| NCP7662/D | 制造商:ONSEMI 制造商全稱:ON Semiconductor 功能描述:Inductorless Voltage Converter |
| NCP7662DR2 | 制造商:ONSEMI 制造商全稱:ON Semiconductor 功能描述:INDUCTORLESS VOLTAGE CONVERTER |
| NCP7662P | 制造商:Rochester Electronics LLC 功能描述:- Bulk 制造商:ON Semiconductor 功能描述: |
| NCP7800 | 制造商:ONSEMI 制造商全稱:ON Semiconductor 功能描述:1.0 A Positive Voltage Regulators |
| NCP7805ACTG | 功能描述:穩(wěn)壓二極管 ANA 1A 5V VREG RoHS:否 制造商:Vishay Semiconductors 齊納電壓:12 V 電壓容差:5 % 電壓溫度系數(shù):0.075 % / K 齊納電流: 功率耗散:3 W 最大反向漏泄電流:3 uA 最大齊納阻抗:7 Ohms 最大工作溫度:+ 150 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:DO-214AC 封裝:Reel |
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