Datasheet TC7660SCOA, TC7660SMJA, TC7660SEPA, TC7660SEOA, TC7660SEJA Datasheet (TelCom Semiconductor)

SUPER CHARGE PUMP DC-TO-DC VOLTAGE CONVERTER

EVALUATION

KIT

AVAILABLE

FEATURES

GENERAL DESCRIPTION

1

TC7660S

2

■ Oscillator boost from 10kHz to 45kHz

■ Converts +5V Logic Supply to ±5V System

■ Wide Input Voltage Range ....................1.5V to 12V

■ Efficient Voltage Conversion.........................99.9%

■ Excellent Power Efficiency ...............................98%

■ Low Power Supply..............................80µA @ 5 V

■ Low Cost and Easy to Use

— Only Two External Capacitors Required

■ Available in Small Outline (SOIC) Package

■ Improved ESD Protection ..................... Up to 10kV

■ No External Diode Required for High Voltage

Operation

ORDERING INFORMATION

Temperature

Part No. Package Range

TC7660SCOA 8-Pin SOIC 0°C to +70°C
TC7660SCPA 8-Pin Plastic DIP 0°C to +70°C
TC7660SEJA 8-Pin CerDIP – 40°C to +85°C
TC7660SEOA 8-Pin SOIC – 40°C to +85°C
TC7660SEPA 8-Pin Plastic DIP – 40°C to +85°C
TC7660SMJA 8-Pin CerDIP – 55°C to +125°C

TC7660EV Evaluation Kit for

Charge Pump Family

The TC7660S is a pin-compatible upgrade to the Indus­try standard TC7660 charge pump voltage converter. It
converts a +1.5V to +12V input to a corresponding -1.5V to

-12V output using only two low-cost capacitors, eliminating
inductors and their associated cost, size and EMI. Added
features include an extended supply range to 12V, and a

IN

frequency boost pin for higher operating frequency, allowing
the use of smaller external capacitors.

The on-board oscillator operates at a nominal frequency
of 10kHz. Frequency is increased to 45kHz when pin 1 is
connected to V+. Operation below 10kHz (for lower supply
current applications) is possible by connecting an external
capacitor from OSC to ground (with pin 1 open).

The TC7660S is available in both 8-pin DIP and 8-pin
small outline (SOIC) packages in commercial and extended
temperature ranges.

PIN CONFIGURATION (DIP and SOIC)

Boost
CAP

GND

CAP

1

+

2
3

–

4

TC7660SCPA
TC7660SEJA
TC7660SEPA

+

8

V

7

OSC
LOW

6

VOLTAGE (LV)

5

V

OUT

Boost

CAP

GND

CAP

1

+

2
3

–

4

TC7660SCOA
TC7660SEOA

+

8

V
OSC

7

LOW

6

VOLTAGE (LV)
V

5

OUT

3

4

5

FUNCTIONAL BLOCK DIAGRAM

LV

1

7

6

BOOST

OSC

TELCOM SEMICONDUCTOR, INC.

RC

OSCILLATOR

TC7660S

INTERNAL

VOLTAGE

REGULATOR

÷ 2

VOLTAGE–

LEVEL

TRANSLATOR

V+CAP

82

3

GND

+

6

LOGIC

NETWORK

4

5

CAP

V

OUT

–

7

8

TC7660S-14 9/16/96

4-69

TC7660S

SUPER CHARGE PUMP DC-TO-DC

VOLTAGE CONVERTER

ABSOLUTE MAXIMUM RATINGS*

Supply Voltage ......................................................... +13V

LV, Boost, OSC Inputs

Voltage (Note 1) ......................... – 0.3V to (V+ +0.3V)

for V+ <5.5V

(V+ – 5.5V) to (V+ +0.3V)

for V+ >5.5V

Current Into LV (Note 1).......................20µA for V+ >3.5V

Output Short Duration (V
Power Dissipation (TA ≤ 70°C) (Note 2)

CerDIP............................................................800mW

Plastic DIP ......................................................730mW

SOIC...............................................................470mW

ELECTRICAL CHARACTERISTICS: T

≤ 5.5V) .........Continuous

SUPPLY

= +25°C, V+ = 5V, C

A

Operating Temperature Range

C Suffix ..................................................0°C to +70°C

E Suffix ............................................. – 40°C to +85°C

M Suffix........................................... – 55°C to +125°C

Storage Temperature Range ................– 65°C to +150°C

Lead Temperature (Soldering, 10 sec) .................+300°C

*Static-sensitive device. Unused devices must be stored in conductive
material. Protect devices from static discharge and static fields. Stresses
above those listed under "Absolute Maximum Ratings" may cause perma­nent damage to the device. These are stress ratings only and functional
operation of the device at these or any other conditions above those
indicated in the operation sections of the specifications is not implied.
Exposure to absolute maximum rating conditions for extended periods may
affect device reliability.

= 0, Test Circuit (Figure 1), unless otherwise

OSC

indicated.

Symbol Parameter Test Conditions Min Typ Max Unit

+

I

+

I

+

V

H

+

V

L

R

OUT

F

OSC

P

EFF

V

OUT EFF

Z

OSC

NOTES: 1. Connecting any input terminal to voltages greater than V+ or less than GND may cause destructive latch-up. It is recommended that no

Supply Current RL = ∞ — 80 160 µA
(Boost pin OPEN or GND) 0°C ≤ T

– 40°C ≤ T

≤ +70°C — — 180

A

≤ +85°C — — 180

A

– 55°C ≤ TA ≤ +125°C — — 200

Supply Current 0°C ≤ TA ≤ +70°C — — 300 µA
(Boost pin = V

+

) – 40°C ≤ TA ≤ +85°C — — 350

– 55°C ≤ TA ≤ +125°C — — 400

Supply Voltage Range, High Min ≤ TA ≤ Max, 3 — 12 V

RL = 10 kΩ, LV Open

Supply Voltage Range, Low Min ≤ TA ≤ Max, 1.5 — 3.5 V

RL = 10 kΩ, LV to GND

Output Source Resistance I

= 20mA — 60 100 Ω

OUT

I

= 20mA, 0°C ≤ TA ≤ +70°C — 70 120

OUT

I

= 20mA, – 40°C ≤ TA ≤ +85°C — 70 120

OUT

I

= 20mA, – 55°C ≤ TA ≤ +125°C — 105 150

OUT

V+ = 2V, I
0°C ≤ T

= 3 mA, LV to GND

OUT

≤ +70°C — — 250 Ω

A

– 55°C ≤ TA ≤ +125°C — — 400

Oscillator Frequency Pin 7 open; Pin 1 open or GND — 10 — kHz

Boost Pin = V

+

—45—

Power Efficiency RL = 5 kΩ; Boost Pin Open 96 98 — %

≤ TA ≤ T

T

MIN

Boost Pin = V

; Boost Pin Open 95 98 —

MAX

+

—88—
Voltage Conversion Efficiency RL = ∞ 99 99.9 — %
Oscillator Impedance V+ = 2V — 1 — MΩ

V+ = 5V — 100 — kΩ

inputs from sources operating from external supplies be applied prior to "power up" of the TC7660S.

2. Derate linearly above 50°C by 5.5mW/°C.

4-70

TELCOM SEMICONDUCTOR, INC.

SUPER CHARGE PUMP DC-TO-DC

V

+

GND

S

3

S

1

S

2

S

4

C

2

V

OUT

= – V

IN

C

1

VOLTAGE CONVERTER

Detailed Description

1

TC7660S

The TC7660S contains all the necessary circuitry to
implement a voltage inverter, with the exception of two
external capacitors, which may be inexpensive 10 µF polar­ized electrolytic capacitors. Operation is best understood by
considering Figure 2, which shows an idealized voltage
inverter. Capacitor C1 is charged to a voltage V+ for the half
cycle when switches S1 and S3 are closed. (Note: Switches
S2 and S4 are open during this half cycle.) During the second
half cycle of operation, switches S2 and S4 are closed, with
S1 and S3 open, thereby shifting capacitor C1 negatively by
V+ volts. Charge is then transferred from C1 negatively by V+
volts. Charge is then transferred from C1 to C2, such that the
voltage on C2 is exactly V+, assuming ideal switches and no
load on C2.

The four switches in Figure 2 are MOS power switches;
S1 is a P-channel device, and S2, S3 and S4 are N-channel
devices. The main difficulty with this approach is that in
integrating the switches, the substrates of S3 and S4 must
always remain reverse-biased with respect to their sources,
but not so much as to degrade their ON resistances. In
addition, at circuit start-up, and under output short circuit
conditions (V
and the substrate bias adjusted accordingly. Failure to
accomplish this will result in high power losses and probable
device latch-up.

This problem is eliminated in the TC7660S by a logic
network which senses the output voltage (V
with the level translators, and switches the substrates of S
and S4 to the correct level to maintain necessary reverse
bias.

+

V

+

C

1

10µF

= V+), the output voltage must be sensed

OUT

) together

OUT

1
2

TC7660S

3
4

8
7

*

6
5

C

OSC

3

I

S

+

V

(+5V)

I

L

R

L

V

O

The voltage regulator portion of the TC7660S is an
integral part of the anti-latch-up circuitry. Its inherent voltage
drop can, however, degrade operation at low voltages. To
improve low-voltage operation, the “LV” pin should be
connected to GND, disabling the regulator. For supply
voltages greater than 3.5V, the LV terminal must be left
open to ensure latch-up-proof operation and prevent device
damage.

Theoretical Power Efficiency
Considerations

In theory, a capacitive charge pump can approach
100% efficiency if certain conditions are met:

(1) The drive circuitry consumes minimal power.

(2) The output switches have extremely low ON

(3) The impedances of the pump and reservoir

The TC7660S approaches these conditions for nega­tive voltage multiplication if large values of C1 and C2 are
used. Energy is lost only in the transfer of charge
between capacitors if a change in voltage occurs. The
energy lost is defined by:

Figure 2. Idealized Charge Pump Inverter

resistance and virtually no offset.

capacitors are negligible at the pump frequency.

2

E = 1/2 C1 (V

1

– V

2

)

2

2

3

4

5

6

7

NOTE: For large values of C

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of C

and C2 should be increased to 100µF.

1

Figure 1. TC7660S Test Circuit

OSC

C

2

10µF

+

(>1000pF), the values

V1 and V2 are the voltages on C1 during the pump and
transfer cycles. If the impedances of C1 and C2 are relatively
high at the pump frequency (refer to Figure 2) compared to
the value of RL, there will be a substantial difference in
voltages V1 and V2. Therefore, it is desirable not only to
make C2 as large as possible to eliminate output voltage
ripple, but also to employ a correspondingly large value for
C1 in order to achieve maximum efficiency of operation.

4-71

8

TC7660S

SUPER CHARGE PUMP DC-TO-DC

VOLTAGE CONVERTER

Dos and Don'ts

• Do not exceed maximum supply voltages.

• Do not connect the LV terminal to GND for supply
voltages greater than 3.5V.

• Do not short circuit the output to V+ supply for voltages
above 5.5V for extended periods; however, transient
conditions including start-up are okay.

• When using polarized capacitors in the inverting mode,
the + terminal of C1 must be connected to pin 2 of the
TC7660S and the + terminal of C2 must be connected
to GND.

Simple Negative Voltage Converter

Figure 3 shows typical connections to provide a nega­tive supply where a positive supply is available. A similar
scheme may be employed for supply voltages anywhere in
the operating range of +1.5V to +12V, keeping in mind that
pin 6 (LV) is tied to the supply negative (GND) only for supply
voltages below 3.5V.

+

V

The output characteristics of the circuit in Figure 3 are
those of a nearly ideal voltage source in series with 70Ω.
Thus, for a load current of –10mA and a supply voltage of
+5V, the output voltage would be –4.3V.

The dynamic output impedance of the TC7660S is due,
primarily, to capacitive reactance of the charge transfer
capacitor (C1). Since this capacitor is connected to the
output for only 1/2 of the cycle, the equation is:

2

XC = = 3.18Ω,

2πf C

1

where f = 10kHz and C1 = 10µF.

Paralleling Devices

Any number of TC7660S voltage converters may be
paralleled to reduce output resistance (Figure 4). The reser­voir capacitor, C2, serves all devices, while each device
requires its own pump capacitor, C1. The resultant output
resistance would be approximately:

R

(of TC7660S)

R

OUT

=

OUT

n (number of devices)

C

10µF

1
2

+

1

NOTES:*

C

1

TC7660S

3
4

Figure 3. Simple Negative Converter

1
2

TC7660S

3
4

"1"

8
7
6
5

+

V

8
7
6
5

V

*

OUT

C

2

10µF

+

1
2

TC7660S

C

1

3

"n"

4

8

R

7
6
5

L

C

2

+

4-72

Figure 4. Paralleling Devices Lowers Output Impedance

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SUPER CHARGE PUMP DC-TO-DC
VOLTAGE CONVERTER

+

V

1

TC7660S

10µF

NOTES:

*

1. V

1
2

+

= –n(V+) for 1.5V ≤ V+ ≤ 12V

OUT

3
4

TC7660S

"1"

8
7
6
5

Figure 5. Increased Output Voltage by Cascading Devices

10µF

Cascading Devices

The TC7660S may be cascaded as shown (Figure 5) to
produce larger negative multiplication of the initial supply
voltage. However, due to the finite efficiency of each device,
the practical limit is 10 devices for light loads. The output
voltage is defined by:

V

= –n (VIN)

OUT

where n is an integer representing the number of devices
cascaded. The resulting output resistance would be ap­proximately the weighted sum of the individual TC7660S
R

values.

OUT

Changing the TC7660S Oscillator Frequency

It may be desirable in some applications (due to noise or
other considerations) to increase the oscillator frequency.
Pin 1, frequency boost pin may be connected to V+ to
increase oscillator frequency to 45kHz from a nominal of
10kHz for an input supply voltage of 5.0 volts. The oscillator
may also be synchronized to an external clock as shown in
Figure 6. In order to prevent possible device latch-up, a 1kΩ
resistor must be used in series with the clock output. In a

+

V

CMOS
GATE

V

OUT

10µF

+

10µF

+

V

1
2

+

3

TC7660S

4

Figure 6. External Clocking

8

1 kΩ

7
6
5

1
2

+

10µF

+

situation where the designer has generated the external
clock frequency using TTL logic, the addition of a 10kΩ pull­up resistor to V+ supply is required. Note that the pump
frequency with external clocking, as with internal clocking,
will be ¹⁄₂ of the clock frequency. Output transitions occur on
the positive-going edge of the clock.

It is also possible to increase the conversion efficiency
of the TC7660S at low load levels by lowering the oscillator
frequency. This reduces the switching losses, and is achieved
by connecting an additional capacitor, C
Figure 7. Lowering the oscillator frequency will cause an
undesirable increase in the impedance of the pump (C1) and
the reservoir (C2) capacitors. To overcome this, increase the
values of C1 and C2 by the same factor that the frequency
has been reduced. For example, the addition of a 100pF
capacitor between pin 7 (OSC) and pin 8 (V+) will lower the
oscillator frequency to 1kHz from its nominal frequency of
10kHz (a multiple of 10), and necessitate a corresponding
increase in the values of C1 and C2 (from 10µF to 100µF).

3
4

TC7660S

"n"

8
7
6
5

+

V

OUT

10µF

, as shown in

OSC

Positive Voltage Multiplication

The TC7660S may be employed to achieve positive
voltage multiplication using the circuit shown in Figure 8. In
this application, the pump inverter switches of the TC7660S
are used to charge C1 to a voltage level of V+–VF (where V
is the supply voltage and VF is the forward voltage drop of
diode D1). On the transfer cycle, the voltage on C1 plus the
supply voltage (V+) is applied through diode D2 to capacitor
C2. The voltage thus created on C2 becomes (2V+) – (2VF),
or twice the supply voltage minus the combined forward
voltage drops of diodes D1 and D2.

The source impedance of the output (V
on the output current, but for V+ = 5V and an output current
of 10mA, it will be approximately 60Ω.

) will depend

OUT

2

*

3

4

5

6

+

7

8

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4-73

TC7660S

SUPER CHARGE PUMP DC-TO-DC

VOLTAGE CONVERTER

+

V

1
2

+

C

1

TC7660S

3
4

Figure 7. Lowering Oscillator Frequency

8
7
6
5

C

OSC

V

OUT

C

2

+

Combined Negative Voltage Conversion
and Positive Supply Multiplication

Figure 9 combines the functions shown in Figures 3 and
8 to provide negative voltage conversion and positive volt­age multiplication simultaneously. This approach would be,
for example, suitable for generating +9V and –5V from an
existing +5V supply. In this instance, capacitors C1 and C
perform the pump and reservoir functions, respectively, for
the generation of the negative voltage, while capacitors C
and C4 are pump and reservoir, respectively, for the multi­plied positive voltage. There is a penalty in this configuration
which combines both functions, however, in that the source
impedances of the generated supplies will be somewhat
higher due to the finite impedance of the common charge
pump driver at pin 2 of the device.

Efficient Positive Voltage
Multiplication/Conversion

Since the switches that allow the charge pumping op­eration are bidirectional, the charge transfer can be per­formed backwards as easily as forwards. Figure 10 shows
a TC7660S transforming –5V to +5V (or +5V to +10V, etc.).
The only problem here is that the internal clock and switch­drive section will not operate until some positive voltage has
been generated. An initial inefficient pump, as shown in
Figure 9, could be used to start this circuit up, after which it

will bypass the other (D1 and D2 in Figure 9 would never turn
on), or else the diode and resistor shown dotted in Figure 10
can be used to "force" the internal regulator on.

Voltage Splitting

The same bidirectional characteristics used in Figure 10
can also be used to split a higher supply in half, as shown in
Figure 11. The combined load will be evenly shared be­tween the two sides. Once again, a high value resistor to the
LV pin ensures start-up. Because the switches share the
load in parallel, the output impedance is much lower than in
the standard circuits, and higher currents can be drawn from
the device. By using this circuit, and then the circuit of Figure
5, +15V can be converted (via +7.5V and –7.5V) to a nominal
–15V, though with rather high series resistance (~250Ω).

+

V

3

2

Figure 9. Combined Negative Converter and Positive Multiplier

1
2

TC7660S

3
4

+

C

1

8
7
6
5

+

C

2

+

D

1

V
(2 V+) – (2 VF)

D

2

+

OUT

Negative Voltage Generation for
Display ADCs

The TC7106 is designed to work from a 9V battery. With
a fixed power supply system, the TC7106 will perform
conversions with input signal referenced to power supply
ground.

V

OUT

C

=

C

= –V

3

4

+

4-74

+

V

1
2

TC7660S

3
4

Figure 8. Positive Voltage Multiplier

8

D

7
6
5

1

+

Negative Supply Generation for
4¹⁄₂ Digit Data Acquisition System

V

=

2

+

OUT

(2 V+) – (2 VF)

C

2

D

C

1

The TC7135 is a 4¹⁄₂ digit ADC operating from ±5V
supplies. The TC7660S provides an inexpensive –5V source.
(See AN16 and AN17 for TC7135 interface details and
software routines.)

TELCOM SEMICONDUCTOR, INC.

SUPER CHARGE PUMP DC-TO-DC
VOLTAGE CONVERTER

C

10µF

V

OUT

1
2

+

1

3
4

TC7660S

8
7
6
5

1 MΩ

= –V

V

–

–

INPUT

+

10µF

R

R

L1

V

OUT

V+–V

L2

1

TC7660S

+

V

+

50µF

50µF

=

–

2

+
–

50µF

100 kΩ

+

–

1
2
3
4

TC7660S

8
7

1 MΩ

6
5

2

3

–

V

Figure 10. Positive Voltage Multiplier

TYPICAL CHARACTERISTICS

Unloaded Osc Freq vs. Temperature

12

10

8

6

4

2

OSCILLATOR FREQUENCY (kHz)

0

-40 -20 0 20 40 10060 80

TEMPERATURE (°C)

Supply Current vs. Temperature

(with Boost Pin = V

1000

VIN = 5V

VIN = 12V

)

IN

Figure 11. Splitting a Supply in Half

Unloaded Osc Freq vs. Temperature

60

with Boost Pin = V

50

40

30

20

10

OSCILLATOR FREQUENCY (kHz)

0

-40 -20 0 20 40 10060 80

TEMPERATURE (°C)

IN

VIN = 12V

Voltage Conversion

101.0

4

VIN = 5V

5

6

800

600

(µA)

DD

400

I

200

0

-40 -20 0 20 40 10060 80

TEMPERATURE (°C)

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VIN = 12V

VIN = 5V

100.5

100.0

99.5

99.0

98.5

VOLTAGE CONVERSION EFFICIENCY (%)

98.0
112111098756423

INPUT VOLTAGE VIN (V)

Without Load

7

10K Load

TA = 25°C

8

4-75

TC7660S

TYPICAL CHARACTERISTICS (Cont.)

SUPER CHARGE PUMP DC-TO-DC

VOLTAGE CONVERTER

Output Source Resistance vs. Supply Voltage

100

70
50

30

I

= 20mA

OUT

T

= 25°C

A

OUTPUT SOURCE RESISTANCE (Ω)

10

1.5 1211.510.59.58.57.55.5 6.54.52.5 3.5

SUPPLY VOLTAGE (V)

Output Voltage vs. Output Current

0

-2

(V)

-4

OUT

-6

-8

-10

OUTPUT VOLTAGE V

-12
0 1009080706040 503010 20

OUTPUT CURRENT (mA)

Output Source Resistance vs. Temperature

100

80

60

40

20

OUTPUT SOURCE RESISTANCE (Ω)

0

-40 -20 0 20 40 10060 80

TEMPERATURE (°C)

VIN = 2.5V

VIN = 5.5V

Power Conversion Efficiency vs. Load

100

90
80
70

Boost Pin = V

60
50
40
30
20

POWER EFFICIENCY (%)

10

0

4.5

3.0

2.0

1.5

1.0

LOAD CURRENT (mA)

6.0

7.5

Boost Pin = Open

+

9.0

15.0

10.0

20.0

25.0

30.0

35.0

40.0

50.0

55.0

60.0

Supply Current vs. Temperature

200
175
150

(µA)

DD

125
100

75
50

SUPPLY CURRENT I

25

0

-40 -20 0 20 40 10060 80

TEMPERATURE (°C)

4-76

VIN = 12.5V

VIN = 5.5V

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