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PDF TC2684 Data sheet ( Hoja de datos )
| Número de pieza | TC2684 | |
| Descripción | (TC2682 - TC2684) Inverting Charge Pump Voltage Doublers | |
| Fabricantes | Microchip Technology | |
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Obsolete Device
TC2682/TC2683/TC2684
Inverting Charge Pump Voltage Doublers
Features
• Small 8-Pin MSOP Package
• Operates from 1.8V to 5.5V
• 120 Ohms (typ) Output Resistance
• 99% Voltage Conversion Efficiency
• Only 3 External Capacitors Required
• Power-Saving Shutdown Mode
• Low Active Supply Current
- 95μA (typ) for TC2682
- 225μA (typ) for TC2683
- 700μA (typ) for TC2684
Applications
• LCD Panel Bias
• Cellular Phones PA Bias
• Pagers
• PDAs, Portable Data Loggers
• Battery-Powered Devices
Device Selection Table
Part
Number
Package
Osc.
Freq.
(kHz)
Operating
Temp.
Range
TC2682EUA 8-Pin MSOP 12 -40°C to +85°C
TC2683EUA 8-Pin MSOP 35 -40°C to +85°C
TC2684EUA 8-Pin MSOP 125 -40°C to +85°C
Package Type
8-Pin MSOP
C1– 1
C2+ 2
C2– 3
VOUT 4
TC2682
TC2683
TC2684
8 NC
7 C1+
6 VIN
5 GND
General Description
The TC2682/TC2683/TC2684 are CMOS charge pump
converters that provide an inverted doubled output
from a single positive supply. An on-board oscillator
provides the clock and only three external capacitors
are required for full circuit implementation. Switching
frequencies are 12kHz for the TC2682, 35kHz for the
TC2683, and 125kHz for the TC2684.
Low output source impedance (typically 120Ω),
provides output current up to 10mA. The TC2682/
TC2683/TC2684 feature a 1.8V to 5.5V operating
voltage range and high efficiency, which make them an
ideal choice for a wide variety of applications requiring
a negative doubled voltage derived from a single
positive supply (for example: generation of -7.2V from
a +3.6V lithium cell or -10V generated from a +5V logic
supply).
The minimum external part count and small physical
size make this family of products useful for a wide
variety of negative bias power supply applications.
Functional Block Diagram
+ C1+
C1
C1–
VIN Input
C2+ TC2682
+ TC2683
C2 C2– TC2684
GND
VOUT
VOUT = -(2 x VIN)
– COUT
+
C1 must have a voltage rating ≥ VIN
C2 and COUT must have a voltage rating ≥ 2VIN
© 2005 Microchip Technology Inc.
DS21548C-page 1
1 page  
TC2682/TC2683/TC2684
4.0 APPLICATIONS INFORMATION
4.1 Output Voltage Considerations
The TC2682/TC2683/TC2684 perform inverting
voltage conversions but do not provide any type of
regulation. The output voltage will droop in a linear
manner with respect to the output load current. The
value of the equivalent output resistance is
approximately 120Ω nominal at +25°C and VIN = +5V.
In this particular case, the output is approximately -10V
at very light loads and will droop according to the
equation below:
VDROOP = IOUT x ROUT
4.2 Capacitor Selection
In order to maintain the lowest output resistance and
output ripple voltage, it is recommended that low ESR
capacitors be used. Additionally, larger values of C1
and C2 will lower the output resistance and larger
values of COUT will reduce output ripple.
Note:
For proper charge pump operation, C1
must have a voltage rating greater than or
equal to VIN, while C2 and COUT must have
a voltage rating greater than or equal to
2VIN.
Table 4-1 shows various values of C1/C2 and the
corresponding output resistance values for VIN = 5V
@ +25°C.
Table 4-2 shows the output voltage ripple for various
values of COUT (again assuming VIN = 5V @ +25°C).
The VRIPPLE values assume a 1mA output load current
and a 0.1Ω ESRCOUT.
TABLE 4-1: OUTPUT RESISTANCE
VS. C1/C2 (ESR = 0.1Ω)
C1, C2
(μF)
0.33
1
3.3
TC2682
ROUT(Ω)
633
262
120
TC2683
ROUT(Ω)
184
120
95
TC2684
ROUT(Ω)
120
102
84
TABLE 4-2:
OUTPUT VOLTAGE RIPPLE
VS. COUT2 (ESR = 0.1Ω)
IOUT = 1mA
COUT
(μF)
0.33
1
3.3
TC2682
VRIPPLE
(mV)
192
63
17
TC2683
VRIPPLE
(mV)
60
21
8
TC2684
VRIPPLE
(mV)
27
16
7
4.3 Input Supply Bypassing
The VIN input should be capacitively bypassed to
reduce AC impedance and minimize noise effects due
to the switching internal to the device. It is recom-
mended that a large value capacitor (at least equal to
C1) be connected from VIN to GND for optimal circuit
performance.
4.4 Inverting Voltage Doubler
The most common application for the TC2682/TC2683/
TC2684 devices is the inverting voltage doubler
(Figure 4-1). This application uses three external
capacitors: C1, C2 and COUT.
Note: A power supply bypass capacitor is
recommended.
The output is equal to -2VIN plus any voltage drops due
to loading. Refer to Table 4-1 and Table 4-2 for
capacitor selection guidelines.
FIGURE 4-1:
DUAL VOLTAGE
INVERTER TEST CIRCUIT
VIN
+
CIN
+
C1
+
C2
7 C1+
6
VIN
1 C1– TC2682
2
C2+
TC2683
TC2684
4
VOUT
3 C2–
GND
COUT
+
5
RL
VOUT
Device
TC2682
TC2683
TC2684
CIN
3.3μF
1μF
0.33μF
C1
3.3μF
1μF
0.33μF
C2
3.3μF
1μF
0.33μF
COUT
3.3μF
1μF
0.33μF
4.5 Layout Considerations
As with any switching power supply circuit, good layout
practice is recommended. Mount components as close
together as possible to minimize stray inductance and
capacitance. Also use a large ground plane to minimize
noise leakage into other circuitry.
© 2005 Microchip Technology Inc.
DS21548C-page 5
5 Page | ||
| Páginas | Total 10 Páginas | |
| PDF Descargar | [ Datasheet TC2684.PDF ] | |
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