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参数资料
| 型号： | TC7662AMJAG |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHED CAPACITOR CONVERTER, 12 kHz SWITCHING FREQ-MAX, CDIP8 |
| 封装： | CERDIP-8 |
| 文件页数： | 13/14页 |
| 文件大小： | 458K |
| 代理商： | TC7662AMJAG |
TC7662A
DS21468B-page 8
2002 Microchip Technology Inc.
4.5
Changing the TC7662A Oscillator
Frequency
It is possible to increase the conversion efficiency of
the TC7662A at low load levels by lowering the
oscillator frequency. This reduces the switching losses,
and is shown in Figure 4-5. However, lowering the
oscillator frequency will cause an undesirable increase
in the impedance of the pump (CP) and reservoir (CR)
capacitors; this is overcome by increasing the values of
CP and CR by the same factor that the frequency has
been reduced. For example, the addition of a 100pF
capacitor between pin 7 (OSC) and VDD will lower the
oscillator frequency to 2kHz from its nominal frequency
of 12kHz (multiple of 6), and thereby necessitate a
corresponding increase in the value of CP and CR (from
10
F to 68F).
FIGURE 4-5:
LOWERING OSCILLATOR
FREQUENCY
4.6
Positive Voltage Doubling
The TC7662A may be employed to achieve positive
voltage doubling using the circuit shown in Figure 4-6.
In this application, the pump inverter switches of the
TC7662A are used to charge CP to a voltage level of
VDD – VF (where VDD is the supply voltage and VF is
the forward voltage on CP plus the supply voltage (VDD)
applied through diode D2 to capacitor CR). The voltage
thus created on CR becomes (2 VDD) – (2 VF), or twice
the supply voltage minus the combined forward voltage
drops of diodes D1 and D2.
The source impedance of the output (VOUT) will depend
on the output current, but for VDD = 5V and an output
current of 10 mA, it will be approximately 60
.
FIGURE 4-6:
POSITIVE VOLTAGE
MULTIPLIER
4.7
Combined Negative Voltage
Conversion and Positive Supply
Multiplication
Figure 4-7 combines the functions shown in Figure 4-1
and Figure 4-6 to provide negative voltage conversion
and positive voltage doubling simultaneously. This
approach would be, for example, suitable for generat-
ing +9V and -5V from an existing +5V supply. In this
instance, capacitors C1 and C3 perform the pump and
reservoir functions, respectively, for the generation of
the negative voltage, while capacitors C2 and C4 are
pump and reservoir, respectively, for the doubled
positive voltage. There is a penalty in this configuration
which combines both functions, however, in that the
source impedances of the generated supplies will be
somewhat higher due to the finite impedance of the
common charge pump driver at pin 2 of the device.
FIGURE 4-7:
COMBINED NEGATIVE
CONVERTER AND
POSITIVE DOUBLER
4.8
Voltage Splitting
The same bidirectional characteristics can be used to
split a higher supply in half, as shown in Figure 4-8.
The combined load will be evenly shared between the
two sides. Because the switches share the load in
parallel, the output impedance is much lower than in
the standard circuits, and higher currents can be drawn
from the device. By using this circuit, and then the
circuit of Figure 4-4, +15V can be converted (via +7.5V
and -7.5V) to a nominal -15V, though with rather high
series resistance (~250
).
FIGURE 4-8:
SPLITTING A SUPPLY IN
HALF
1
2
3
4
8
7
6
5
+
VOUT
COSC
+
TC7662A
10
F
10
F
VDD
1
2
3
4
8
7
6
5
VOUT =
(2 VDD) – (2 VF)
+
CR
D1
D2
+
CP
TC7662A
VDD
1
2
3
4
8
7
6
5
+
VDD
VOUT =
(2 VDD) – (2 VF)
C1
D1
+
C3
C4
VOUT =
-(VDD – VF)
C2
TC7662A
D2
+
RL1
RL2
VOUT =
VDD – V
–
2
50
F
50
F
VDD
V –
50
F
+
1
2
8
7
TC7662A
3
4
6
5
+
–
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相关代理商/技术参数 |
参数描述 |
|---|---|
| TC7662B | 制造商:MICROCHIP 制造商全称:Microchip Technology 功能描述:CHARGE PUMP DC-TO-DC VOLTAGE CONVERTER |
| TC7662BC0A | 制造商:Texas Instruments 功能描述: |
| TC7662BCOA | 功能描述:电荷泵 High Voltage RoHS:否 制造商:Maxim Integrated 功能:Inverting, Step Up 输出电压:- 1.5 V to - 5.5 V, 3 V to 11 V 输出电流:100 mA 电源电流:1 mA 最大工作温度:+ 70 C 封装 / 箱体:SOIC-8 Narrow 封装:Tube |
| TC7662BCOA | 制造商:Microchip Technology Inc 功能描述:DC/DC CONVERTER SMD 7662 SOIC8 |
| TC7662BCOA713 | 功能描述:电荷泵 High Voltage RoHS:否 制造商:Maxim Integrated 功能:Inverting, Step Up 输出电压:- 1.5 V to - 5.5 V, 3 V to 11 V 输出电流:100 mA 电源电流:1 mA 最大工作温度:+ 70 C 封装 / 箱体:SOIC-8 Narrow 封装:Tube |
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