TC3682
TC3683
TC3684
Inverting Charge Pump Voltage Doublers with Active Low Shutdown
FEATURES
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Small 8-Pin MSOP Package
Operation 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
......................... 95
µ
A (typ.) for TC3682
..........................225
µ
A (typ.) for TC3683
..........................700
µ
A (typ.) for TC3684
s
Fully Compatible with 1.8V Logic Systems
GENERAL DESCRIPTION
The TC3682, TC3683 and TC3684 are CMOS charge
pump converters that provide an inverted doubled output
from a single positive supply. An on-board oscillator pro-
vides the clock and only three external capacitors are
required for full circuit implementation. Switching frequen-
cies are 12kHz for the TC3682, 35kHz for the TC3683, and
125kHz for the TC3684. When the SHDN pin is held at a
logic low, 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), pro-
vides output current up to 10mA. The TC3682, TC3683 and
TC3684 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: genera-
tion of -7.2V from a +3.6V lithium cell or –10V generated
from a +5V logic supply).
The minimum external parts count, small physical size,
and shutdown mode make this family of products useful for
a wide variety of negative bias power supply applications.
TYPICAL APPLICATIONS
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LCD Panel Bias
Cellular Phones PA Bias
Pagers
PDAs, Portable Data Loggers
Battery Powered Devices
TYPICAL OPERATING CIRCUIT
ORDERING INFORMATION
Part No.
Package
8-Pin MSOP
8-Pin MSOP
8-Pin MSOP
Osc Freq (kHz) Temp. Range
12
35
125
– 40°C to +85°C
– 40°C to +85°C
– 40°C to +85°C
TC3682EUA
TC3683EUA
TC3684EUA
+
C1
C1+
C1–
C2+
V
IN
TC3682
TC3683
SHDN
TC3684
INPUT
ON
OFF
PIN CONFIGURATION
+
C2
C2–
GND
8-Pin MSOP
V
OUT
V
OUT
= -(2xV
IN
)
– C
OUT
+
C1-
1
C2+
2
C2-
3
V
OUT
4
TC3682
TC3683
TC3684
8
SHDN
7
C1+
6
V
IN
5
GND
Notes:
1) C1 must have a voltage rating greater
than or equal to V
IN
2) C2 and C
OUT
must have a voltage rating greater
than or equal to 2V
IN
2001 Microchip Technology Inc.
DS21556A
TC3682/3/4-1 8/14/00
Inverting Charge Pump Voltage
Doublers with Active Low Shutdown
TC3682
TC3683
TC3684
ABSOLUTE MAXIMUM RATINGS*
Input Voltage (V
IN
to GND) ......................... +6.0V, - 0.3V
Output Voltage (V
OUT
to GND) ................. -12.0V, + 0.3V
Current at V
OUT
Pin ................................................ 20mA
Short-Circuit Duration V
OUT
to GND ...................Indefinite
Operating Temperature Range ............... -40°C to +85°C
Power Dissipation (T
A
≤
70°C) 8-Pin MSOP ............... 320mW
Storage Temperature (Unbiased) ......... - 65
°C
to +150°C
Lead Temperature (Soldering, 10sec) .................. +260°C
*This is a stress rating only and functional operation of the device at these
or any other conditions above those indicated in the operational sections of
the specifications is not implied. Exposure to absolute maximum rating
conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS:
T
A
= -40°C to +85°C, V
IN
= + 5V, C1 = C2 = 3.3µF (TC3682); C1 = C2 =
1µF (TC3683); C1 = C2 = 0.33µF (TC3684); SHDN = GND, unless otherwise noted. Typical values are at T
A
= +25°C
Symbol
I
DD
Parameter
Supply Current
Device
TC3682
TC3683
TC3684
All
All
All
TC3682
TC3683
TC3684
All
All
All
All
TC3682
TC3683
TC3684
Test Conditions
SHDN = V
IN
SHDN = V
IN
SHDN = V
IN
SHDN = GND, V
IN
= +5V
R
LOAD
= 1kΩ
R
LOAD
= 1kΩ
Min
—
—
—
—
1.8
—
8.4
24.5
65
1.4
—
95
—
—
—
—
Typ
95
225
700
0.5
—
—
12
35
125
—
—
99
120
1800
600
200
Max
160
480
1500
2
—
5.5
15.6
45.5
170
—
0.4
—
170
—
—
—
Unit
µA
I
SHDN
V
MIN
V
MAX
F
OSC
Shutdown Supply Current
Minimum Supply Voltage
Maximum Supply Voltage
Oscillator Frequency
µA
V
V
kHz
V
IH
V
IL
V
EFF
R
OUT
T
WK
Shutdown Input
Logic High
Shutdown Input
Logic Low
Voltage Conversion Efficiency
Output Resistance
Wake-Up Time From
Shutdown Mode
V
IN
= V
MIN
to V
MAX
V
IN
= V
MIN
to V
MAX
R
LOAD
=
∞
I
LOAD
= 0.5mA to10mA
R
LOAD
= 2kΩ
V
V
V
Ω
µsec
NOTES:
1. Capacitor contribution is approximately 20% of the output impedance (ESR = 1/pump frequency x capacitance)
PIN DESCRIPTION
Pin No.
1
2
3
4
5
6
7
8
Symbol
C1
–
C2
+
C2
–
V
OUT
GND
V
IN
C1
+
SHDN
Description
C1 Commutation Capacitor Negative Terminal
C2 Commutation Capacitor Positive Terminal
C2 Commutation Capacitor Negative Terminal
Doubling Inverting Charge Pump Output (– 2 x V
IN
)
Ground
Positive Power Supply Input
C1 Commutation Capacitor Positive Terminal
Shutdown Input (Active Low)
TC3682/3/4-1 8/14/00
2
2001 Microchip Technology Inc.
DS21556A
Inverting Charge Pump Voltage
Doublers with Active Low Shutdown
TC3682
TC3683
TC3684
DETAILED DESCRIPTION
The TC3682, TC3683 and TC3684 charge pumps per-
form –2x multiplication of the voltage applied to the V
IN
pin.
Conversion is performed using two
synchronous
switching
matrices and three external capacitors. When the shut-
down input is held at a logic low, both stages go into a very
low power mode of operation consuming less than 1µA of
supply current.
Figure 1 (below) is a block diagram representation of the
TC3682, TC3683 and TC3684 architecture. The first switch-
ing stage inverts the voltage present at V
IN
and the second
stage uses ‘–V
IN
’ generated from the first stage to produce
the ‘–2x’ output function from the second stage switching matrix.
Each device contains an on-board oscillator that syn-
chronously controls the operation of the charge pump switch-
ing matrices. The TC3682 synchronously switches at 12kHz,
the TC3683 synchronously switches at 35kHz, and the
TC3684 synchronously switches at 125kHz. The different
oscillator frequencies for this device family allow the user to
trade-off capacitor size versus supply current. Faster oscil-
lators can use smaller external capacitors, but will consume
more supply current (see Electrical Characteristics Table).
When the shutdown input is in a low state, the oscillator
and both switch matrices are powered off placing the TC3682,
TC3683 and TC3684 in the shutdown mode. When the V
IN
supply input is powered from an external battery, the shut-
down mode minimizes power consumption, which in turn will
extend the life of the battery.
APPLICATIONS INFORMATION
Output Voltage Considerations
The TC3682, TC3683 and TC3684 perform inverting
voltage conversions but do not provide any type of regula-
tion. The output voltage will droop in a linear manner with
respect to the respective load currents. The value of the
equivalent output resistance of the ‘-V
IN
’ output is approxi-
mately 50Ω nominal at +25°C and V
IN
= +5V. The value of
the ‘-2V
IN
’ output and is approximately 140Ω nominal at
+25°C and V
IN
= +5V. In this particular case, ‘-V
IN
’ is
approximately – 5V and ‘–2V
IN
’ is approximately –10V at
very light loads, and each stage will droop according to the
equation below:
V
DROOP
= I
OUT
x R
OUT
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 C
OUT
will
reduce output ripple.
NOTE: For proper charge pump
operation, C1 must have a voltage rating greater than or
equal to V
IN
, while C2 and C
OUT
must have a voltage
rating greater than or equal to 2V
IN
.
Table 1 shows various values of C1/C2 and the corre-
sponding output resistance values for V
IN
=5V @ +25°C.
Table 2 shows the output voltage ripple for various
values of C
OUT
(again assuming V
IN
= 5V @ +25
o
C). The
V
RIPPLE
values assume a 1mA output load current and a
0.1Ω ESR
COUT
.
VIN
+
C1
—VIN
SWITCH MATRIX
(1st STAGE)
+
ENABLE
COUT1
Table 1. Output Resistance vs. C1/C2 (ESR = 0.1Ω).
OSCILLATOR
ENABLE
C1,C2
(
µ
F)
0.33
1
3.3
TC3682
R
OUT
(
Ω
)
633
262
120
TC3683
R
OUT
(
Ω
)
184
120
95
TC3684
R
OUT
(
Ω
)
120
102
84
+
C2
—2VIN
SWITCH MATRIX
(2nd STAGE)
+
ENABLE
COUT2
Table 2. Output Voltage Ripple vs. C
OUT
(ESR = 0.1Ω) I
OUT
= 1mA
SHDN
C
OUT
(
µ
F)
0.33
1
3.3
3
TC3682 V
RIPPLE
(mV)
192
63
17
TC3683 V
RIPPLE
(mV)
60
21
8
TC3684 V
RIPPLE
(mV)
27
16
7
TC3682/3/4-1 8/14/00
Figure 1. Functional Block Diagram
2001 Microchip Technology Inc.
DS21556A
Inverting Charge Pump Voltage
Doublers with Active Low Shutdown
TC3682
TC3683
TC3684
Input Supply Bypassing
TheV
IN
input should be capacitively bypassed to reduce
AC impedance and minimize noise effects due to the internal
switching in the device. It is recommended that a large value
capacitor (at least equal to C1) be connected from V
IN
to
GND for optimal circuit performance.
Shutdown Input
The TC3682, TC3683 and TC3684 are enabled when
SHDN is high, and disabled when SHDN is low. This input
cannot be allowed to float. (If SHDN is not required, see the
TC2682/2683/2684 data sheet.) The SHDN input should be
limited to 0.3V above V
IN
.
Inverting Voltage Doubler
The most common application for the TC3682/3683/
3684 devices is the inverting voltage doubler (Figure 2).
This application uses three external capacitors: C1, C2, and
C
OUT
(NOTE: a power supply bypass capacitor is recom-
mended). The output is equal to –2V
IN
plus any voltage drop
due to loading. Refer to Tables 1 and 2 for capacitor
selection guidelines.
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.
TC3682 Demo Card
The TC3682 DEMO Card is a 2.0” x 2.0” card containing
both a TC3682 and a TC682 that allow the user to compare
the operation of each approach for generating a –2X func-
tion. Each circuit is fully assembled with the required
external capacitors along with variable load resistors that
allow the user to vary the output load current of each stage.
For convenience, several test points and jumpers are avail-
able for measuring various voltages and currents on the
demo board.
Figure 3 is a schematic of the TC3682 DEMO Card, and
Figure 4 shows the assembly drawing and artwork for the
board. Table 3 lists the voltages that are monitored by the
test points and Table 4 lists the currents that can be
measured using the jumpers.
Table 3. TC3682 DEMO Card Test Points
Device
TC3682
TC3683
TC3684
C
IN
C1
C2
3.3µF 3.3µF
3.3µF
1µF
1µF
1µF
0.33µF 0.33µF 0.33µF
C
OUT
3.3µF
1µF
0.33µF
TEST POINT
TP1
TP2
TP3
TP4
TP5
TP6
TP7
TP8
TP9
VOLTAGE MEASUREMENT
V
IN
[+1.8V TO +5V]
GROUND
GROUND
TC682 (U1) SUPPLY VOLTAGE
TC682 (U1) OUTPUT VOLTAGE [V
OUT1
]
TC3682 (U2) SUPPLY VOLTAGE
TC3682 (U2) OUTPUT VOLTAGE [V
OUT2
]
TC3682 (U2) SHDN INPUT VOLTAGE
DEMO CARD /SHUTDOWN INPUT
V
IN
C
IN
7
C1
1
2
C2
3 C2–
C1–
C2+
TC3682
TC3683
TC3684
–2V
IN
GND
5
4
C
OUT
V
OUT
R
L
C1+
6
V
IN
8
SHDN
Table 4. TC3682 DEMO Card Jumpers
JUMPER
J1
J2
J3
J4
J5
J6
CURRENT MEASUREMNT
TC682 (U1) QUIESCENT CURRENT
TC3682 (U2) QUIESCENT CURRENT
TC682 (U1) V
OUT1
LOAD CURRENT
TC3682 (U2) V
OUT2
LOAD CURRENT
TC3682 (U2) SHDN INPUT CURRENT
CONNECT DEMO CARD /SHUTDOWN
INPUT TO GND
Figure 2. Dual Voltage Inverter Test Circuit
TC3682/3/4-1 8/14/00
4
2001 Microchip Technology Inc.
DS21556A
Inverting Charge Pump Voltage
Doublers with Active Low Shutdown
TC3682
TC3683
TC3684
Figure 3. TC3682 DEMO Card Schematic
Figure 4. TC3682 DEMO Card Assembly Drawing and Artwork
2001 Microchip Technology Inc.
DS21556A
5
TC3682/3/4-1 8/14/00
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