MICROCHIP TC7660 Technical data
M
Charge Pump DC-to-DC Voltage Converter
TC7660
Features
• Wide Input Voltage Range: +1.5V to +10V
• Efficient Voltage Conversion (99.9%, typ)
• Excellent Power Efficiency (98%, typ)
• Low Power Consumption: 80 µA (typ) @ V
• Low Cost and Easy to Use
- Only Two External Capacitors Required
• Available in 8-Pin Small Outline (SOIC), 8-Pin
PDIP and 8-Pin CERDIP Packages
• Improved ESD Protection (3 kV HBM)
• No External Diode Required for High-Voltage
Operation
IN
= 5V
Applications
• RS-232 Negative Power Supply
• Simple Conversion of +5V to ±5V Supplies
• Voltage Multiplication V
• Negative Supplies for Data Acquisition Systems
and Instrumentation
OUT
= ± n V
+
Functional Block Diagram
Package Types
PDIP/CERDIP/SOIC
+
8
V
7
OSC
LOW
6
VOLTAGE (LV)
5
V
OUT
CAP
GND
CAP
NC
1
+
2
TC7660
3
-
4
General Description
The TC7660 is a pin-compatible replacement for the
industry standard 7660 charge pump voltage
converter. It converts a +1.5V to +10V input to a
corresponding -1.5V to -10V output using only two low
cost capacitors, eliminating inductors and their
associated cost, size and electromagnetic interference
(EMI).
The on-board oscillator operates at a nominal
frequency of 10 kHz. Operation below 10 kHz (for
lower supply current applications) is possible by
connecting an external capacitor from OSC to ground.
The TC7660 is available in 8-Pin PDIP, 8-Pin Small
Outline (SOIC) and 8-Pin CERDIP packages in
commercial and extended temperature ranges.
+
+
V
CAP
82
OSC
LV
7
6
RC
Oscillator
Internal
Internal
Vol t age
Vol t age
Regulator
Regulator
÷
2
TC7660
2002 Microchip Technology Inc. DS21465B-page 1
Vol t age
Level
Translator
3
GND
Logic
Network
4
CAP-
5
V
OUT
TC7660
1.0 ELECTRICAL CHARACTERISTICS
Absolute Maximum Ratings*
Supply Voltage .............................................................+10.5V
LV and OSC Inputs Voltage: (Note 1)
.............................................. -0.3V to V
..................................... (V
+
– 5.5V) to (V+) for V+ > 5.5V
Current into LV ......................................... 20 µA for V
Output Short Duration (V
Package Power Dissipation: (T
8-Pin CERDIP ....................................................800 mW
≤ 5.5V)............... Continuous
SUPPLY
≤ 70°C)
A
8-Pin PDIP .........................................................730 mW
8-Pin SOIC .........................................................470 mW
Operating Temperature Range:
C Suffix....................................................... 0°C to +70°C
I Suffix .....................................................-25°C to +85°C
E Suffix ....................................................-40°C to +85°C
M Suffix .................................................-55°C to +125°C
Storage Temperature Range .........................-65°C to +160°C
ESD protection on all pins (HBM) ................... ..............≥ 3kV
Maximum Junction Temperature ........... ....................... 150°C
for V+ < 5.5V
SS
+
> 3.5V
ELECTRICAL SPECIFICATIONS
Electrical Characteristics: Unless otherwise noted, specifications measured over operating temperature range with V+ = 5V,
C
= 0, refer to test circuit in Figure 1-1.
OSC
Parameters Sym Min Typ Max Units Conditions
R
OUT
f
OSC
P
EFF
V
OUTEFF
Z
OSC
+
I
+
H
+
L
Supply Current
Supply Voltage Range, High V
Supply Voltage Range, Low V
Output Source Resistance
Oscillator Frequency
Power Efficiency
Voltage Conversion Efficiency
Oscillator Impedance
Note 1: Destructive latch-up may occur if voltages greater than V
—80180µAR
3.0 — 10 V Min ≤ TA ≤ Max, RL = 10 kΩ, LV Open
1.5 — 3.5 V Min ≤ T
—70100Ω I
——120 I
——130 I
—104150 I
—150300 V
—160600 V
— 10 — kHz Pin 7 open
95 98 — % RL = 5 kΩ
97 99.9 — % RL = ∞
—1.0—MΩ V+ = 2V
—100—kΩ V
* Notice: Stresses above those listed under "Maximum Ratings" may cause permanent damage to the device. This is a
stress rating only and functional operation of the device at
those or any other conditions above those indicated in the
operational sections of this specification is not intended. Exposure to maximum rating conditions for extended periods may
affect device reliability.
I
C
10 µF
1
2
+
3
TC7660
1
4
8
7
6
5
C
OSC
+
I
L
R
C
2
10 µF
FIGURE 1-1: TC7660 Test Circuit.
= ∞
L
≤ Max, R
A
=20 mA, TA = +25°C
OUT
=20 mA, TA ≤ +70°C (C Device)
OUT
=20 mA, TA ≤ +85°C (E and I Device)
OUT
=20 mA, TA ≤ +125°C (M Device)
OUT
+
= 2V, I
+
= 2V, I
+
= 5V
OUT
≤ +70°C
A
OUT
A
0°C ≤ T
-55°C ≤ T
+
or less than GND are supplied to any input pin.
= 10 kΩ, LV to GND
L
= 3 mA, LV to GND
= 3 mA, LV to GND
≤ +125°C (M Device)
S
V
(+5V)
L
V
+
OUT
DS21465B-page 2 2002 Microchip Technology Inc.
TC7660
5
0+25+75+100
5
50-55
)
SU
GE
k
2.0 TYPICAL PERFORMANCE CURVES
Note: The graphs and tables provided following this note are a statistical summary based on a limited number of
samples and are provided for informational purposes only. The performance characteristics listed herein
are not tested or guaranteed. In some graphs or tables, the data presented may be outside the specified
operating range (e.g., outside specified power supply range) and therefore outside the warranted range.
Note: Unless otherwise indicated, C
12
10
8
6
PPLY VOLTAGE RAN
4
SUPPLY VOLTAGE (V)
2
0
-2
TEMPERATURE (C
+
= C2 = 10 µF, ESRC1 = ESRC2 = 1 Ω, TA = 25°C. See Figure 1-1.
1
+12
FIGURE 2-1: Operating Voltage vs. Temperature.
10k
1k
100Ω
OUTPUT SOURCE RESISTANCE (Ω)
10Ω
SUPPLY VOLTAGE (V)
7 8
6543210
FIGURE 2-2: Output Source Resistance vs. Supply Voltage.
100
98
I
= 1 mA
OUT
96
94
92
I
= 15 mA
OUT
90
88
86
84
82
V+ = +5V
POWER CONVERSION EFFICIENCY (%)
80
100 1k
OSCILLATOR FREQUENCY (Hz)
10
FIGURE 2-4: Power Conversion Efficiency vs. Oscillator Frequency.
500
I
= 1 mA
OUT
450
400
200
150
V+ = +2V
100
V + = +5V
50
OUTPUT SOURCE RESISTANCE (Ω)
0
-55 -25 0 +25 +50 +75 +100 +125
TEMPERATURE (°C)
FIGURE 2-5: Output Source Resistance vs. Temperature.
10k
1k
100
OSCILLATOR FREQUENCY (Hz)
10
1
10 100 1000 10k
OSCILLATOR CAPACITANCE (pF)
V+ = +5V
FIGURE 2-3: Frequency of Oscillation vs. Oscillator Capacitance.
FIGURE 2-6: Unloaded Oscillator Frequency vs. Temperature.
20
V+ = +5V
18
16
14
12
10
8
OSCILLATOR FREQUENCY (kHz)
6
-55
-25 0 +25 +50 +75 +100 +125
TEMPERATURE (°C)
2002 Microchip Technology Inc. DS21465B-page 3
TC7660
Note: Unless otherwise indicated, C
0
-1
-2
-3
-4
-5
-6
-7
OUTPUT VOLTAGE (V)
-8
-9
-10
0
10 20 30 40 50 60 70 80 90 100
OUTPUT CURRENT (mA)
= C2 = 10 µF, ESRC1 = ESRC2 = 1 Ω, TA = 25°C. See Figure 1-1.
1
LV OPEN
FIGURE 2-7: Output Voltage vs. Output Current.
100
90
80
70
60
50
40
30
20
10
POWER CONVERSION EFFICIENCY (%)
0
1.5 3.0 4.5 6.0 7.5 9.0
LOAD CURRENT (mA)
V+ = 2V
20
18
16
14
12
10
8
6
SUPPLY CURRENT (mA)
4
2
0
5
V+ = +5V
4
3
2
1
0
-1
-2
OUTPUT VOLTAGE (V)
-3
SLOPE 55
-4
-5
0
10 20 30 40 50 60 70 80
LOAD CURRENT (mA)
Ω
FIGURE 2-10: Output Voltage vs. Load Current.
100
90
80
70
60
50
40
30
20
10
POWER CONVERSION EFFICIENCY (%)
0
10 20 30 40 50 60
LOAD CURRENT (mA)
V+ = +5V
100
90
80
70
60
50
40
30
SUPPLY CURRENT (mA)
20
10
0
FIGURE 2-8: Supply Current and Power Conversion Efficiency vs. Load Current.
2
V+ = +2V
1
0
-1
OUTPUT VOLTAGE (V)
-2
0
SLOPE 150Ω
123 4 5 67 8
LOAD CURRENT (mA)
FIGURE 2-9: Output Voltage vs. Load Current.
FIGURE 2-11: Supply Current and Power Conversion Efficiency vs. Load Current.
DS21465B-page 4 2002 Microchip Technology Inc.
3.0 PIN DESCRIPTIONS
The descriptions of the pins are listed in Table 3-1.
TABLE 3-1: PIN FUNCTION TABLE
Pin No. Symbol Description
1 NC No connection
2CAP
3 GND Ground terminal
4CAP
5V
6 LV Low voltage pin. Connect to GND for V+ < 3.5V
7 OSC Oscillator control input. Bypass with an external capacitor to slow the oscillator
8V
OUT
+
+
Charge pump capacitor positive terminal
-
Charge pump capacitor negative terminal
Output voltage
Power supply positive voltage input
TC7660
3.1 Charge Pump Capacitor (CAP+)
Positive connection for the charge pump capacitor, or
flying capacitor, used to transfer charge from the input
source to the output. In the voltage-inverting configuration, the charge pump capacitor is charged to the input
voltage during the first half of the switching cycle. During the second half of the switching cycle, the charge
pump capacitor is inverted and charge is transferred to
the output capacitor and load.
It is recommended that a low ESR (equivalent series
resistance) capacitor be used. Additionally, larger
values will lower the output resistance.
3.2 Ground (GND)
Input and output zero volt reference.
3.3 Charge Pump Capacitor (CAP-)
Negative connection for the charge pump capacitor, or
flying capacitor, used to transfer charge from the input
to the output. Proper orientation is imperative when
using a polarized capacitor.
3.4 Output Voltage (V
Negative connection for the charge pump output
capacitor. In the voltage-inverting configuration, the
charge pump output capacitor supplies the output load
during the first half of the switching cycle. During the
second half of the switching cycle, charge is restored to
the charge pump output capacitor.
It is recommended that a low ESR (equivalent series
resistance) capacitor be used. Additionally, larger
values will lower the output ripple.
OUT
)
3.5 Low Voltage Pin (LV)
The low voltage pin ensures proper operation of the
internal oscillator for input voltages below 3.5V. The low
voltage pin should be connected to ground (GND) for
input voltages below 3.5V. Otherwise, the low voltage
pin should be allowed to float.
3.6 Oscillator Control Input (OSC)
The oscillator control input can be utilized to slow down
or speed up the operation of the TC7660. Refer to
Section 5.4, “Changing the TC7660 Oscillator
Frequency”, for details on altering the oscillator
frequency.
3.7 Power Supply (V+)
Positive power supply input voltage connection. It is
recommended that a low ESR (equivalent series resistance) capacitor be used to bypass the power supply
input to ground (GND).
2002 Microchip Technology Inc. DS21465B-page 5
TC7660
4.0 DETAILED DESCRIPTION
4.1 Theory of Operation
The TC7660 charge pump converter inverts the voltage
applied to the V
phase operation (Figure 4-1). During the first phase,
switches S
are closed. C1 charges to the voltage applied to the V
pin, with the load current being supplied from C2. During the second phase, switches S
and switches S
ferred from C
supplied from C
+
V
GND
FIGURE 4-1: Ideal Switched Capacitor Inverter.
In this manner, the TC7660 performs a voltage inversion, but does not provide regulation. The average output voltage will drop in a linear manner with respect to
load current. The equivalent circuit of the charge pump
inverter can be modeled as an ideal voltage source in
series with a resistor, as shown in Figure 4-2.
FIGURE 4-2: Switched Capacitor Inverter Equivalent Circuit Model.
The value of the series resistor (R
the switching frequency, capacitance and equivalent
series resistance (ESR) of C
tance of switches S
approximation for R
equation:
+
pin. The conversion consists of a two-
and S4 are open and switches S1 and S
2
and S4 are closed
and S3 are open. Charge is trans-
1
to C2, with the load current being
1
.
1
S
1
S
3
S
2
+
C
1
S
4
R
OUT
2
+
C
2
V
= -V
OUT
V
OUT
-
+
V
+
) is a function of
OUT
and C2 and the on-resis-
1
, S2, S3 and S4. A close
1
is given in the following
OUT
IN
EQUATION
1
R
OUT
--------- ------------- -------
f
PUMP
C1×
++ +=
8R
4ESRC1ESR
SW
C2
Where:
f
OSC
3
+
f
PUMP
R
SW
ESR
ESR
-----------
=
2
on-resistance of the switches=
equivalent series resistance of C
=
C1
equivalent series resistance of C
=
C2
1
2
4.2 Switched Capacitor Inverter Power Losses
The overall power loss of a switched capacitor inverter
is affected by four factors:
1. Losses from power consumed by the internal
oscillator, switch drive, etc. These losses will
vary with input voltage, temperature and
oscillator frequency.
2. Conduction losses in the non-ideal switches.
3. Losses due to the non-ideal nature of the
external capacitors.
4. Losses that occur during charge transfer from
C
to C2 when a voltage difference between the
1
capacitors exists.
Figure 4-3 depicts the non-ideal elements associated
with the switched capacitor inverter power loss.
S
SW
SW
1
++
C
1
ESR
C1
S
3
R
+
V
I
DD
+
-
R
FIGURE 4-3: Non-Ideal Switched Capacitor Inverter.
The power loss is calculated using the following
equation:
EQUATION
P
LOSSIOUT
2
× I
S
SW
SW
OUT
ESR
2
C
2
I
LOAD
OUT
C2
S
4
V+×+=
DD
R
R
R
DS21465B-page 6 2002 Microchip Technology Inc.
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