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PDF TC168x Data sheet ( Hoja de datos )
| Número de pieza | TC168x | |
| Descripción | Inverting Charge Pump Voltage Doublers with Active High Shutdown | |
| Fabricantes | Microchip Technology | |
| Logotipo |  |
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M TC1682/TC1683/TC1684
Inverting Charge Pump Voltage Doublers with Active High Shutdown
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 TC1682
- 225µA (typ) for TC1683
- 700µA (typ) for TC1684
• Fully Compatible with 1.8V Logic Systems
Applications
• LCD Panel Bias
• Cellular Phones PA Bias
• Pagers
• PDAs, Portable Data Loggers
• Battery-Powered Devices
Device Selection Table
Part
Number
TC1682EUA
TC1683EUA
TC1684EUA
Package
8-Pin MSOP
8-Pin MSOP
8-Pin MSOP
Osc.
Freq.
(kHz)
Operating
Temp.
Range
12 -40°C to +85°C
35 -40°C to +85°C
125 -40°C to +85°C
Package Type
8-Pin MSOP
C1– 1
C2+ 2
C2– 3
VOUT 4
TC1682
TC1683
TC1684
8 SHDN
7 C1+
6 VIN
5 GND
General Description
The TC1682/TC1683/TC1684 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 TC1682, 35kHz for the
TC1683, and 125kHz for the TC1684. When the SHDN
pin is held at a logic high, the device goes into a very
low power mode of operation consuming less than 1µA
(typ) of supply current.
Low output source impedance (typically 120Ω),
provides output current up to 10mA. The TC1682/
TC1683/TC1684 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, small physical size
and shutdown mode feature make this family of
products useful for a wide variety of negative bias
power supply applications.
Functional Block Diagram
+ C1+
C1
VIN
C1–
SHDN
C2+ TC1682
+ TC1683
C2 C2– TC1684
Input
OFF
ON
GND
VOUT
VOUT = -(2 x VIN)
– COUT
+
C1 must have a voltage rating ≥ VIN
C2 and COUT must have a voltage rating ≥ 2VIN
2002 Microchip Technology Inc.
DS21537B-page 1
1 page  
TC1682/TC1683/TC1684
4.0 APPLICATIONS INFORMATION
4.1 Output Voltage Considerations
The TC1682/TC1683/TC1684 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
TC1682
ROUT(Ω)
633
262
120
TC1683
ROUT(Ω)
184
120
95
TC1684
ROUT(Ω)
120
102
84
TABLE 4-2:
OUTPUT VOLTAGE RIPPLE
VS. COUT2 (ESR = 0.1Ω)
IOUT = 1mA
COUT
(µF)
TC1682
VRIPPLE
(mV)
TC1683
VRIPPLE
(mV)
TC1684
VRIPPLE
(mV)
0.33 192
1 63
3.3 17
60
21
8
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
recommended that a large value capacitor (at least
equal to C1) be connected from VIN to GND for optimal
circuit performance.
4.4 Shutdown Input
The TC1682/TC1683/TC1684 is enabled when SHDN
is low, and disabled when SHDN is high. This input
cannot be allowed to float. (If SHDN is not required, see
the TC2682/TC2683/TC2684 data sheet.) The SHDN
input should be limited to 0.3V above VIN.
4.5 Inverting Voltage Doubler
The most common application for the TC1682/TC1683/
TC1684 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:
INVERTING VOLTAGE
DOUBLER TEST CIRCUIT
VIN
+
CIN
+
C1
+
C2
7 C1+
68
VIN SHDN
1 C1– TC1682
2 C2+
TC1683
TC1684
4
VOUT
3 C2–
GND
COUT
+
5
RL
VOUT
Device
TC1682
TC1683
TC1684
CIN
3.3µF
1µF
0.33µF
C1
3.3µF
1µF
0.33µF
C2
3.3µF
1µF
0.33µF
COUT
3.3µF
1µF
0.33µF
4.6 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.
2002 Microchip Technology Inc.
DS21537B-page 5
5 Page | ||
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