+5V TO ± 10V VOL T AGE CONVERTER
FEATURES
EV ALUATION
KIT
A V AILABLE
GENERAL DESCRIPTION
1
TCM680
2
■ 99% Voltage Conversion Efficiency
■ 85% Power Conversion Efficiency
■ Wide Voltage Range .........................+2.0V to +5.5V
■ Only 4 External Capacitors Required
■ Space Saving 8-Pin SOIC Design
APPLICATIONS
■ ±10V From +5V Logic Supply
■ ±6V From a 3V Lithium Cell
■ Handheld Instruments
■ Portable Cellular Phones
■ LCD Display Bias Generator
■ Panel Meters
■ Operational Amplifier Power Supplies
PIN CONFIGURATIONS (DIP AND SOIC)
8
7
6
5
V
C
V
GND
+
V
OUT
+
C
1
V
IN
GND
+
OUT
+
1
IN
V
C
C
C
–
OUT
V
–
1
1
+
2
2
–
2
C
C
C
–
OUT
–
1
+
2
–
2
TCM680CPA
3
TCM680EPA
4
18
2
TCM680COA
3
TCM680EOA
4
7
6
5
The TCM680 is a dual charge pump voltage converter
that develops output voltages of +2VIN and – 2VIN from a
single input voltage of +2.0V to +5.5V. Common applications include ±10V from a single +5V logic supply, and ±6V
from a +3V lithium battery.
The TCM680 is packaged in a space-saving 8-pin
SOIC package and requires only four inexpensive external
capacitors. The charge pumps are clocked by an on-board
8kHz oscillator. Low output source impedances (typically
150Ω) provides maximum output currents of 10mA for each
output. Typical power conversion efficiency is 85%.
High efficiency, small installed size and low cost make
the TCM680 suitable for a wide variety of applications that
need both positive and negative power supplies derived
from a single input voltage.
ORDERING INFORMATION
Part No. Package Temperature
TCM680COA 8-Pin SOIC 0°C to +70°C
TCM680CPA 8-Pin Plastic DIP 0°C to +70°C
TCM680EOA 8-Pin SOIC – 40°C to +85°C
TCM680EPA 8-Pin Plastic DIP – 40°C to +85°C
TC7660EV Charge Pump Family
Evaluation Kit
3
4
5
6
TYPICAL OPERATING CIRCUIT
+5V
C1
4.7µF
C2
4.7µF
GND
2.0V<V
+
+
C
C
C
C
+
1
–
1
+
TCM680
2
–
2
IN
V
IN
GND
< +5.5V
+
V
OUT
–
V
OUT
TELCOM SEMICONDUCTOR, INC.
4.7µFC4
+
+
V
OUT
–
V
OUT
4.7µF
C3
+
GND
7
= (2xVIN)
= (– 2 x VIN)
8
TC660-2 9/4/96
4-13
TCM680
C
1
C
1
C
2
C
3
C
2
V
IN
V
IN
V
OUT
V
OUT
V
OUT
GND
GND
TCM680
4.7µF
4.7µF
10µF
C
4
10µF
8
7
6
54
3
2
1
V
OUT
C
2
R
L
R
L
C
1
–
+
–
–
+
+
+
–
+
–
+5V TO
±10V VOLT AGE CONVERTER
ABSOLUTE MAXIMUM RATINGS*
V
.....................................................................................................+6.0V
IN
+
V
.............................................................................................. +12.0V
OUT
–
V
.............................................................................................– 12.0V
OUT
–
V
Short-Circuit Duration ............................Continuous
OUT
+
V
Current ............................................................75mA
OUT
V
dV/dT.............................................................. 1V/µsec
IN
Power Dissipation (TA ≤ 70°C)
Plastic DIP ......................................................730mW
Small Outline ..................................................470mW
Storage Temperature ............................– 65°C to +150°C
Lead Temperature (Soldering, 10 sec) .................+300°C
*Stresses above those listed in "Absolute Maximum Ratings" may cause
permanent damage to the device. These are stress ratings only and
functional operation of the device at these or other conditions above those
indicated in the operation section of the specification is not implied.
Exposure to the Absolute Maximum Ratings conditions for extended
periods of time may affect device reliability.
ELECTRICAL CHARACTERISTICS: V
= +5V, TA = +25°C, test circuit Figure 1, unless otherwise indicated.
IN
Symbol Parameter Test Conditions Min Typ Max Unit
Supply Voltage Range MIN. ≤ TA ≤ MAX., RL = 2kΩ 2.0 1.5 to 5.5 5.5 V
Supply Current VIN = 3V, RL = ∞ — 0.5 1 mA
= 5V, RL = ∞ —1 2
V
IN
V
= 5V, 0°C ≤ TA ≤ +70°C, RL = ∞ — — 2.5
IN
VIN = 5V, – 40°C ≤ TA ≤ +85°C, RL = ∞ ——3
Negative Charge Pump Output I
Source Resistance I
–
= 10mA, I
L
–
= 5mA, I
L
–
= 10mA, I
I
L
0°C ≤ T
– 40°C ≤ TA ≤ +85°C — — 250
Positive Charge Pump Output I
Source Resistance I
+
= 10mA, I
L
+
= 5mA, I
L
+
I
= 10mA, I
L
0°C ≤ T
– 40°C ≤ TA ≤ +85°C — — 250
F
OSC
P
EFF
V
OUT EFF
TelCom Semiconductor reserves the right to make changes in the circuitry or specifications detailed in this manual at any time without notice. Minimums
and maximums are guaranteed. All other specifications are intended as guidelines only. TelCom Semiconductor assumes no responsibility for the use of
any circuits described herein and makes no representations that they are free from patent infringement.
Oscillator Frequency — 21 — kHz
Power Efficiency RL = 2kΩ —85—%
V
+
OUT
–
OUT
Voltage Conversion Efficiency V
+
= 0mA, VIN = 5V — 140 180 Ω
L
+
= 0mA, VIN = 2.8V — 180 250
L
+
= 0mA, VIN = 5V:
L
≤ +70°C — — 220
A
–
= 0mA, VIN = 5V — 140 180 Ω
L
–
= 0mA, VIN = 2.8V — 180 250
L
–
= 0mA, VIN = 5V:
L
≤ +70°C — — 220
A
, RL = ∞ 97 99 — %
, RL = ∞ 97 99 —
PIN DESCRIPTION
8-Pin
DIP/SOIC
1C
2C
3C
4V
5 GND Input. Device ground.
6VINInput. Power supply voltage.
7C
8V
4-14
Symbol Description
–
1
+
2
–
2
–
OUT
+
1
+
OUT
Input. Capacitor C1 negative terminal.
Input. Capacitor C2 positive terminal.
Input. Capacitor C2 negative terminal.
Output. Negative output voltage (–2VIN).
Input. Capacitor C1 positive terminal.
Output. Positive output voltage (+2VIN)
Figure 1. Test Circuit
TELCOM SEMICONDUCTOR, INC.
+5V TO
±10V VOLT AGE CONVERTER
1
TCM680
DETAILED DESCRIPTION
Phase 1
VSS charge storage – The positive side of capacitors C
and C2 are connected to +5V at the start of this phase. C
then switched to ground and the charge in C
to C
–
. Since C
2
+
is connected to +5V, the voltage potential
2
–
is transferred
1
across capacitor C2 is now 10V.
V
= +5V
IN
–
C
4
+
V
SW1
+
C
1
–
SW2
–5V
Figure 2. Charge Pump – Phase 1
SW3
+
C
2
–
SW4
DD
V
SS
–
C
3
+
+
is
1
Phase 2
VSS transfer – Phase two of the clock connects the
negative terminal of C2 to the VSS storage capacitor C3 and
the positive terminal of C2 to ground, transferring the generated –10V to C3. Simultaneously, the positive side of capacitor C1 is switched to +5V and the negative side is connected
to ground.
V
= +5V
IN
–
C
4
+
V
1
SW1
+
C
1
–
SW2
–5V
Figure 4. Charge Pump – Phase 3
SW3
+
C
2
–
SW4
DD
V
SS
–
C
3
+
Phase 4
VDD transfer – The fourth phase of the clock connects
the negative terminal of C2 to ground, and transfers the
generated 10V across C2 to C4, the VDD storage capacitor.
Again, simultaneously with this, the positive side of capacitor C1 is switched to +5V and the negative side is connected
to ground, and the cycle begins again.
+5V
–
C
4
SW1 SW3
+
C
1
–
SW4SW2
+
+
C
2
–
–10V
V
V
–
C
3
+
2
3
4
DD
SS
5
+5V
–
C
4
SW1 SW3
+
C
–
Figure 3. Charge Pump – Phase 2
+
C
1
2
–
SW4SW2
–10V
+
V
DD
V
SS
–
C
3
+
Phase 3
VDD charge storage – The third phase of the clock is
identical to the first phase – the charge transferred in C
produces –5V in the negative terminal of C1, which is applied
to the negative side of capacitor C2. Since C
voltage potential across C2 is 10V.
TELCOM SEMICONDUCTOR, INC.
+
is at +5V, the
2
Figure 5. Charge Pump – Phase 4
MAXIMUM OPERATING LIMITS
The TCM680 has on-chip zener diodes that clamp V
to 5.8V, V
+
to 11.6V, and V
OUT
the maximum supply voltage or excessive current will be
shunted by these diodes, potentially damaging the chip. The
TCM680 will operate over the entire operating temperature
range with an input voltage of 2V to 5.5V.
1
–
to –11.6V. Never exceed
OUT
6
IN
7
8
4-15
TCM680
+5V TO
±10V VOLT AGE CONVERTER
EFFICIENCY CONSIDERATIONS
Theoretically a charge pump can approach 100% effi-
ciency under the following conditions:
• The charge Pump switches have virtually no offset
and extremely low on resistance
• Minimal power is consumed by the drive circuitry
• The impedances of the reservoir and pump capacitors are negligible
For the TCM680, efficiency is as shown below:
Efficiency V+ = V
Efficiency V– = V
Power Loss =(V
There will be a substantial voltage difference between
+
(V
– VIN) and V
OUT
+
V
OUT
and V
if the impedances of the pump capacitors C
–OUT
/(2VIN)
DD
V
= 2VIN – V
DD
+
V
V
V
= (I
DROP
/(– 2VIN)
SS
= 2VIN – V
SS
–
= (I
DROP
+
)(I
DROP
for the positive pump and between
IN
+
OUT
–
OUT
+
OUT
+
DROP
)(R
–
DROP
)(R
) + (V
+
OUT
–
OUT
)
)
–
DROP
)(I
–
OUT
)
and C2 are high with respect to the output loads.
Larger values of reservoir capacitors C3 and C4 will
reduce output ripple. Larger values of both pump and
reservoir capacitors improve the efficiency. See "Capacitor
Selection" in Applications Section.
APPLICATIONS
Positive and negative Converter
The most common application of the TCM680 is as a
dual charge pump voltage converter which provides positive
and negative outputs of two times a positive input voltage.
The simple circuit of Figure 6 performs this same function
using the TCM680 and external capacitors, C1, C2, C3 and C
Capacitor Selection
The TCM680 requires only 4 external capacitors for
operation. These can be inexpensive polarized aluminum
electrolytic types. For the circuit in Figure 6 the output
characteristics are largely determined by the external
capacitors. An expression for R
below:
+
R
R
OUT
–
OUT
= 4(R
+4(R
+1/(f
=
+4(R
+1/(f
4(R
SW1
SW1
PUMP
SW1
SW1
PUMP
+ R
+ ESRC1 + R
SW2
+ R
SW2
x C1) + 1/(f
+ R
SW2
+ R
SW2
x C1) + 1/(f
+ ESRC1 + R
+ ESRC1 + R
+ ESRC1 + R
Assuming all switch resistances are approximately
equal...
+
R
= 32R
OUT
+1/(f
–
R
= 32R
1
OUT
+1/(f
R
is typically 140Ω at +25°C with VIN = +5V and C1
OUT
+ 8ESRC1 + 8ESRC2 + ESR
SW
x C1) + 1/(f
PUMP
+ 8ESRC1 + 8ESRC2 + ESR
SW
x C1) + 1/(f
PUMP
and C2 as 4.7µF low ESR capacitors. The fixed term
(32RSW) is about 130Ω. It can be seen easily that increasing
or decreasing values of C1 and C2 will affect efficiency by
changing R
. However, be careful about ESR. This term
OUT
can quickly become dominant with large electrolytic capacitors. Table 1 shows R
for various values of C1 and C2
OUT
(assume 0.5Ω ESR). C1 and C4 must be rated at 6VDC or
greater while C2 and C3 must be rated at 12VDC or greater.
Output voltage ripple is affected by C3 and C4. Typically
the larger the value of C3 and C4 the less the ripple for a
given load current. The formula for V
4.
below:
can be derived as shown
OUT
+ R
SW3
x C2) + ESR
PUMP
SW3
x C2) + ESR
PUMP
PUMP
PUMP
SW4
+ R
SW3
+ R
SW4
+ R
SW3
x C2)
x C2)
RIPPLE(p-p)
+ ESRC2)
+ ESRC2)
SW4
+ ESRC2)
+ ESRC2)
SW4
C4
C3
is given
C4
C3
4-16
V
C
22µF
1
22µF
C
2
1
–
C
1
+
2
C
2
TCM680
–
3
C
2
–
V
OUT
Figure 6. Positive and Negative Converter
+
V
OUT
C
V
GND
8
+
7
1
6
IN
54
C
22µF
C
3
22µF
4
V
V
GND
V
+
OUT
IN
–
OUT
+RIPPLE(p-p)
V
–RIPPLE(p-p)
For a 10µF (0.5Ω ESR) capacitor for C3, C4,
f
= 21kHz and I
PUMP
voltage at the output will be less than 100mV. In most
applications (I
1-5µF pump capacitors will suffice. Table 2 shows V
for different values of C3 and C4 (assume 1Ω ESR).
= {1/[2(f
= {1/[2(f
OUT
< = 10mA) 10-20µF output capacitors and
OUT
/3) x C4] + 2(ESRC4)}(I
PUMP
/3) x C3] + 2(ESRC3)}(I
PUMP
= 10mA the peak-to-peak ripple
+
OUT
–
OUT
RIPPLE
)
)
TELCOM SEMICONDUCTOR, INC.
+5V TO
±10V VOLT AGE CONVERTER
1
TCM680
Table 1. R
C1, C2 (µF) R
Table 2. V
C3, C4 (µF) V
vs. C1 ,C2
OUT
OUT
0.1 1089
0.47 339
1 232
3.3 165
4.7 157
10 146
22 141
100 137
RIPPLE (p-p)
0.47 1540
1 734
3.3 236
4.7 172
10 91
22 52
100 27
vs. C3, C4 (I
OUT
RIPPLE
= 10mA)
(Ω)
(mV)
Paralleling Devices
Paralleling multiple TCM680s reduces the output resistance of both the positive and negative converters. The
effective output resistance is the output resistance of a
single device divided by the number of devices. As illustrated in Figure 7, each requires separate pump capacitors
C1 and C2, but all can share a single set of reservoir
capacitors.
±5V Regulated Supplies From A Single
3V Battery
Figure 8 shows a complete ±5V power supply using one
3V battery. The TCM680 provides +6V at V
regulated to +5V by the TC55, and –5V by the negative LDO.
The input to the TCM680 can vary from 3V to 6V without
affecting regulation appreciably. With higher input voltage,
more current can be drawn from the outputs of the TCM680.
With 5V at VIN, 10mA can be drawn from both regulated
outputs simultaneously. Assuming 150Ω source resistance
for both converters, with (I
+
+ IL) = 20mA, the positive charge
L
pump will droop 3V, providing +7V for the negative charge
pump.
+
, which is
OUT
2
3
4
V
IN
GND
10µF
10µF
5
V
+
V
1
–
1
TCM680
+
2
–
2
IN
GND
+
10µF
–
–
V
OUT
10µF
+
–
+
–
+
–
C
C
C
C
+
C
1
–
C
1
+
C
2
–
C
2
IN
TCM680
GND
V
–
OUT
6
NEGATIVE
SUPPLY
–
–
C
OUT
+
22µF
7
Figure 7. Paralleling TCM680 for Lower Output Source Resistance
TELCOM SEMICONDUCTOR, INC.
8
4-17
TCM680
+
3V
–
10µF
10µF
+5V TO
+
–
C
OUT
22µF
+
± 10V VOLTAGE CONVERTER
TC55RP5002Exx
+
V
C
+
–
+
–
1
–
C
1
+
C
2
–
C
2
TCM680
GND
+
IN
V
OUT
V
IN
+6V
V
OUT
V
SS
+
1µF
+5 SUPPLY
–
GROUND
–
1µF
+
–5 SUPPLY
V
–
OUT
–6V
V
SS
V
IN
V
OUT
–
22µF
–
+
C
OUT
NEGATIVE LDO
TC54VC2702Exx
V
IN
V
SS
Figure 8. Split Supply Derived from 3V Battery
V
OUT
LOW BATTERY
4-18
TELCOM SEMICONDUCTOR, INC.
+5V TO
±10V VOLT AGE CONVERTER
TYPICAL CHARACTERISTICS
OUTPUT RESISTANCE (Ω)
300
250
200
150
+
V
Output Resistance vs. V
OUT
or V
–
OUT
IN
C1 – C4 = 10µF
R
OUT
(V)
OUT
V
10.0
9.0
8.0
V
+
OUT
TCM680
–
or V
vs. Load Current
OUT
VIN = 5V
1
2
3
100
1
1.4
1.2
1.0
0.8
0.6
SUPPLY CURRENT (mA)
0.4
0.2
1
2
Supply Current vs. V
2
3
V
(V)
IN
NO LOAD
3
V
(V)
IN
180
160
456
IN
456
Output Source Resistance vs. Temperature
V
= 5V
IN
I
OUT = 10mA
7.0
0
Output Voltage vs. Output Current From V
10.0
9.0
(V)
OUT
V
8.0
7.0
0
OUTPUT CURRENT (mA) From V
5
LOAD CURRENT (mA)
2
4
10
15
4
+–
to V
OUT
OUT
VIN = 5V
5
6810
+
OUT
TO V
–
OUT
6
140
120
OUTPUT SOURCE RESISTANCE (Ω)
100
-50
TELCOM SEMICONDUCTOR, INC.
R
OUT
0
TEMPERATURE (°C)
50 100
7
8
4-19
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