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參數(shù)資料
| 型號： | TC7662AIJA |
| 廠商： | TelCom Semiconductor, Inc. |
| 元件分類： | 圓形連接器 |
| 英文描述： | Circular Connector; No. of Contacts:32; Series:MS27473; Body Material:Aluminum; Connecting Termination:Crimp; Connector Shell Size:18; Circular Contact Gender:Socket; Circular Shell Style:Straight Plug; Insert Arrangement:18-32 RoHS Compliant: No |
| 中文描述： | 電荷泵DC - DC轉(zhuǎn)換器 |
| 文件頁數(shù)： | 3/5頁 |
| 文件大小： | 62K |
| 代理商： | TC7662AIJA |
4-79
TELCOM SEMICONDUCTOR, INC.
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2
8
Note one of its characteristics is ESR (equivalent series
resistance). This parasitic resistance winds up in series with
the load. Thus, both voltage and power conversion effi-
ciency are compromised if a low ESR capacitor is not used.
For example, in the "Test Circuit", changing C
P
and C
R
capacitors from typical ESR to low ESR types, the effective
converter output impedance changed from 45
to 40
, an
improvement of 12%.
This applies to all types of capacitors, including film
types (polyester, polycarbonate etc.).
Some applications information suggests that the ca-
pacitor is not critical and attributes the limiting factor to the
capacitor's reactance value. Let's examine this:
where DS (duty cycle) = 50%.
Thus, Z
C
≈
1.33
at f = 12kHz, where C = 10
μ
F.
For the TC7662A, f = 12,000Hz, and a typical value of
C would be 10
μ
F. This is a reactive impedance of
≈
1.33
.
If the ESR is as great as 5
, the reactive value is not as
critical as it would first appear, since the ESR would dominate.
The 5
value is typical of a general-purpose electrolytic
capacitor.
Synchronizing
The TC7662A may be synchronized by connecting pin
7 of the TC7662A through a 100k resistor in series with a
diode to a negative-going pulse source. The negative pulse
voltage can be +5V with a 5 microsecond duration going
negative to 0V.
TEST CIRCUIT
Figure 2. Synchronization
X
C
=
and Z
C
=X
C
DS
APPLICATIONS INFORMATION
Theory of Operation
The TC7662A is a capacitive charge pump (some-
times called a switched-capacitor circuit), where four
MOSFET switches control the charge and discharge of a
capacitor.
The functional diagram (page 1) shows how the switch-
ing action works. SW1 and SW2 are turned on simulta-
neously, charging C1 to the supply voltage, V
DD
. This
assumes that the ON resistance of the MOSFETs in series
with the capacitor produce a charging time (3 time con-
stants) less than the ON time provided by the oscillator
frequency, as shown:
3 (R
DS(ON)
C1) <C1/(0.5 f
OSC
).
In the next cycle, SW1 and SW2 are turned OFF and,
after a very short interval with all switches OFF (preventing
large currents from occurring due to cross conduction),
SW3 and SW4 are turned ON. The charge in C1 is then
transferred to C
OUT
, BUT WITH THE POLARITY IN-
VERTED. In this way, a negative voltage is derived.
An oscillator supplies pulses to a flip-flop that is fed to a
set of level shifters. These level shifters then drive each set
of switches at one-half the oscillator frequency.
The oscillator has a pin that controls the frequency of
oscillation. Pin 7 can have a capacitor added that is con-
nected to ground. This will lower the frequency of the
oscillator by adding capacitance to the internal timing ca-
pacitor of the TC7662A. (See Oscillator Frequency vs. C
EXT
,
page 5.)
Capacitors
In early charge pump converters, capacitors were not
considered critical due to the high R
DS(ON)
of the MOSFET
switches. In order to understand this, let’s look at a model of
a typical electrolytic capacitor (Figure 1).
1
2
π
f C
TC7662A
1
2
3
4
8
7
5
CP
+
10 μF
COSC
RL
V
(–5V)
OUT
10 μF
CR
IL
IS
V
(+5V)
+
NC
NC
6
+
TTL
Q
Q
100 k
TO PIN 7
TC7662A
Figure 1. Capacitor Equivalent Circuit
EPR
ESL
ESR
C
CHARGE PUMP
DC-TO-DC CONVERTER
TC7662A
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| TC7662AIJA | CHARGE PUMP DC-TO-DC CONVERTER |
| TC7662A | CHARGE PUMP DC-TO-DC CONVERTER |
| TC7662ACPA | CHARGE PUMP DC-TO-DC CONVERTER |
| TC7662AEPA | CHARGE PUMP DC-TO-DC CONVERTER |
| TC7662AMJA | CHARGE PUMP DC-TO-DC CONVERTER |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| TC7662AMJA | 功能描述:電荷泵 High Voltage 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 |
| TC7662B | 制造商:MICROCHIP 制造商全稱: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:電荷泵 High Voltage 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 |
| TC7662BCOA | 制造商:Microchip Technology Inc 功能描述:DC/DC CONVERTER SMD 7662 SOIC8 |
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