TELCOM TC1044SIJA

1
EVALUATION
KIT
AVAILABLE
TC1044S
CHARGE PUMP DC-TO-DC VOLTAGE CONVERTER
FEATURES
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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 Consumption ............ 80µA @ VIN = 5V
Low Cost and Easy to Use
— Only Two External Capacitors Required
RS-232 Negative Power Supply
Available in 8-Pin Small Outline (SOIC) and 8-Pin
Plastic DIP Packages
Improved ESD Protection ..................... Up to 10kV
No External Diode Required for High Voltage
Operation
Frequency Boost Raises FOSC to 45kHz
PIN CONFIGURATION (DIP and SOIC)
BOOST 1
2
GENERAL DESCRIPTION
8 V+
CAP + 2
7 OSC
TC1044SCPA
GND 3 TC1044SEPA 6 LOW
VOLTAGE (LV)
TC1044SIJA
CAP – 4 TC1044SMJA 5 VOUT
CAP + 2
7 OSC
GND 3 TC1044SCOA 6 LOW
VOLTAGE (LV)
TC1044SEOA
5 VOUT
CAP – 4
Part No.
Package
TC1044SCOA
8-Pin SOIC
TC1044SCPA
8-Pin Plastic DIP
TC1044SEOA
8-Pin SOIC
0°C to +70°C
0°C to +70°C
– 40°C to +85°C
TC1044SEPA
8-Pin Plastic DIP
– 40°C to +85°C
TC1044SIJA
8-Pin CerDIP
– 25°C to +85°C
TC1044SMJA
8-Pin CerDIP
– 55°C to +125°C
TC7660EV
Charge Pump Family Evaluation Kit
V+
8
OSC
LV
4
Temp. Range
5
6
FUNCTIONAL BLOCK DIAGRAM
BOOST
3
ORDERING INFORMATION
8 V+
BOOST 1
The TC1044S 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 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 TC1044S is available in both 8-pin DIP and
8-pin small outline (SOIC) packages in commercial and
extended temperature ranges.
CAP +
2
1
7
RC
OSCILLATOR
2
VOLTAGE–
LEVEL
TRANSLATOR
4
CAP –
7
6
5
VOUT
INTERNAL
VOLTAGE
REGULATOR
LOGIC
NETWORK
TC1044S
8
3
GND
TC1044S-12 9/16/96
TELCOM SEMICONDUCTOR, INC.
4-43
CHARGE PUMP DC-TO-DC
VOLTAGE CONVERTER
TC1044S
ABSOLUTE MAXIMUM RATINGS*
Supply Voltage ......................................................... +13V
LV, Boost and 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 (VSUPPLY ≤ 5.5V) ......... Continuous
Lead Temperature (Soldering, 10 sec) ................. +300°C
Package Power Dissipation (TA ≤ 70°C) (Note 2)
8-Pin CerDIP ..................................................800mW
8-Pin Plastic DIP ............................................. 730mW
8-Pin SOIC .....................................................470mW
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 +150°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.
ELECTRICAL CHARACTERISTICS: TA = +25°C, V+ = 5V, COSC = 0, Test Circuit (Figure 1), unless otherwise
indicated.
Symbol
Parameter
I+
Supply Current
I+
Supply Current
(Boost Pin = V+)
+
VH2
Supply Voltage Range, High
+
VL2
Supply Voltage Range, Low
ROUT
Output Source Resistance
FOSC
Oscillator Frequency
PEFF
Power Efficiency
VOUT EFF
ZOSC
Voltage Conversion Efficiency
Oscillator Impedance
Test Conditions
RL = ∞
0°C < TA < +70°C
– 40°C < TA < +85°C
– 55°C < TA < +125°C
0°C < TA < +70°C
– 40°C < TA < +85°C
– 55°C < TA < +125°C
Min ≤ TA ≤ Max,
RL = 10 kΩ, LV Open
Min ≤ TA ≤ Max,
RL = 10 kΩ, LV to GND
IOUT = 20mA
IOUT = 20mA, 0°C ≤ TA ≤ +70°C
IOUT = 20mA, –40°C ≤ TA ≤ +85°C
IOUT = 20mA, –55°C ≤ TA ≤ +125°C
V+ = 2V, IOUT = 3 mA, LV to GND
0°C ≤ TA ≤ +70°C
– 55°C ≤ TA ≤ +125°C
Pin 7 open; Pin 1 open or GND
Boost Pin = V+
RL = 5 kΩ; Boost Pin Open
TMIN < TA < TMAX; Boost Pin Open
Boost Pin = V+
RL = ∞
V+ = 2V
V+ = 5V
Min
Typ
Max
Unit
—
—
—
—
—
—
—
3
80
—
—
—
—
—
—
—
160
180
180
200
300
350
400
12
µA
1.5
—
3.5
V
—
—
—
—
60
70
70
105
100
120
120
150
Ω
—
—
—
—
96
95
—
99
—
—
—
—
10
45
98
97
88
99.9
1
100
250
400
—
—
—
—
—
—
—
—
Ω
µA
V
kHz
%
%
MΩ
kΩ
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
inputs from sources operating from external supplies be applied prior to "power up" of the TC1044S.
2. Derate linearly above 50°C by 5.5mW/°C.
4-44
TELCOM SEMICONDUCTOR, INC.
CHARGE PUMP DC-TO-DC
VOLTAGE CONVERTER
1
TC1044S
Circuit Description
The TC1044S 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 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 (VOUT = V+), the output voltage must be sensed
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 TC1044S by a logic
network which senses the output voltage (VOUT) together
with the level translators, and switches the substrates of S3
and S4 to the correct level to maintain necessary reverse
bias.
V+
S1
S2
2
C1
GND
S3
S4
C2
VOUT = – VIN
Figure 2. Idealized Charge Pump Inverter
The voltage regulator portion of the TC1044S 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
C1
1µF
+
IS
1
8
2
7
3
4
TC1044S
6
COSC*
5
IL
V+
(+5V)
RL
VOUT
+
C2
10µF
NOTE: For large values of COSC (>1000pF), the values
of C1 and C2 should be increased to 100µF.
Figure 1. TC1044S Test Circuit
TELCOM SEMICONDUCTOR, INC.
4
5
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
resistance and virtually no offset.
V+
3
(3) The impedances of the pump and reservoir
capacitors are negligible at the pump frequency.
6
The TC1044S 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:
7
E = 1/2 C1 (V12 – V22)
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.
4-45
8
CHARGE PUMP DC-TO-DC
VOLTAGE CONVERTER
TC1044S
Dos and Don'ts
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 TC1044S 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 C1
• 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
TC1044S and the + terminal of C2 must be connected
to GND.
where f = 10 kHz and C1 = 10µF.
Paralleling Devices
Simple Negative Voltage Converter
Any number of TC1044S 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:
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.
ROUT =
ROUT (of TC1044S)
n (number of devices)
V+
C1
10µF
+
1
8
2
7
3
TC1044S
4
6
+
VOUT*
C2
10µF
5
* NOTES:
Figure 3. Simple Negative Converter
V+
1
8
2
C1
3
4
TC1044S
"1"
7
1
8
6
2
7
5
C1
3
4
TC1044S
"n"
RL
6
5
+
C2
Figure 4. Paralleling Devices Lowers Output Impedance
4-46
TELCOM SEMICONDUCTOR, INC.
CHARGE PUMP DC-TO-DC
VOLTAGE CONVERTER
1
TC1044S
V+
1
2
+
3
10µF
2
8
7
TC1044S
"1"
4
1
6
8
2
+
5
10µF
7
3
TC1044S
6
4
"n"
5
VOUT*
+
* NOTES:
1. VOUT = –n(V+) for 1.5V ≤ V+ ≤ 12V
+
3
10µF
10µF
Figure 5. Increased Output Voltage by Cascading Devices
Cascading Devices
The TC1044S 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:
VOUT = –n(VIN)
where n is an integer representing the number of devices
cascaded. The resulting output resistance would be approximately the weighted sum of the individual TC1044S
ROUT values.
Changing the TC1044S 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+
1
V+
8
1kΩ
2
+
10µF
3
4
CMOS
GATE
7
TC1044S
6
5
VOUT
+
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 TC1044S at low load levels by lowering the oscillator
frequency. This reduces the switching losses, and is achieved
by connecting an additional capacitor, COSC, as shown in
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).
5
6
Positive Voltage Multiplication
The TC1044S may be employed to achieve positive
voltage multiplication using the circuit shown in Figure 8. In
this application, the pump inverter switches of the TC1044S
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 (VOUT) will depend
on the output current, but for V+ = 5V and an output current
of 10mA, it will be approximately 60Ω.
Figure 6. External Clocking
TELCOM SEMICONDUCTOR, INC.
4
4-47
7
8
CHARGE PUMP DC-TO-DC
VOLTAGE CONVERTER
TC1044S
V+
C1
+
1
8
2
7
3
TC1044S
4
COSC
6
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
5
VOUT
C2
+
Figure 7. Lowering Oscillator Frequency
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 C3
perform the pump and reservoir functions, respectively, for
the generation of the negative voltage, while capacitors C2
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.
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+
VOUT = –V+
1
8
2
7
3
+
C1
TC1044S
4
6
D1
5
+
D2
1
8
2
7
3
4
TC1044S
Figure 9. Combined Negative Converter and Positive Multiplier
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.
Negative Supply Generation for
4¹⁄₂ Digit Data Acquisition System
D1
VOUT =
(2 V+) – (2 VF)
D2
6
5
VOUT =
(2 V +) – (2 VF)
C4
Efficient Positive Voltage
Multiplication/Conversion
V+
C3
+
C2
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 TC1044S 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
+
+
+
C1
C2
The TC7135 is a 4¹⁄₂ digit ADC operating from ±5V
supplies. The TC1044S provides an inexpensive –5V source.
(See AN16 and AN17 for TC7135 interface details and
software routines.)
Figure 8. Positive Voltage Multiplier
4-48
TELCOM SEMICONDUCTOR, INC.
CHARGE PUMP DC-TO-DC
VOLTAGE CONVERTER
1
TC1044S
V+
VOUT = –V–
1
8
2
+
C1
10µF
+
7
TC1044S
6
4
50 µF
VOUT = +
V + –V –
50
2
µF
RL2
10µF
1 MΩ
3
2
+
RL1
1
8
2
7
1 MΩ
3
100
kΩ
100
kΩ
TC1044S
6
4
5
5
50
µF
V– INPUT
+
V–
3
Figure 11. Splitting a Supply in Half
Figure 10. Positive Voltage Conversion
TYPICAL CHARACTERISTICS
Unloaded Osc Freq vs. Temperature
60
OSCILLATOR FREQUENCY (kHz)
OSCILLATOR FREQUENCY (kHz)
12
10
8
VIN = 5V
6
4
VIN = 12V
2
0
-40
-20
0
20
40
60
80
50
40
VIN = 5V
VIN = 12V
20
10
0
-40
100
-20
0
VOLTAGE CONVERSION EFFICIENCY (%)
800
VIN = 12V
600
400
200
VIN = 5V
0
20
40
40
60
80
100
60
TEMPERATURE (°C)
TELCOM SEMICONDUCTOR, INC.
80
6
Voltage Conversion
1000
-20
20
TEMPERATURE (°C)
Supply Current vs. Temperature
(with Boost Pin = VIN)
0
-40
5
30
TEMPERATURE (°C)
IDD (µA)
4
Unloaded Osc Freq vs. Temperature
with Boost Pin = VIN
100
101.0
100.5
Without Load
100.0
7
99.5
10K Load
99.0
98.5
TA = 25°C
98.0
1
2
3
4
5
6
7
8
9
10 11 12
INPUT VOLTAGE VIN (V)
4-49
8
CHARGE PUMP DC-TO-DC
VOLTAGE CONVERTER
TC1044S
TYPICAL CHARACTERISTICS (Cont.)
Output Source Resistance vs. Supply Voltage
Output Source Resistance vs. Temperature
100
OUTPUT SOURCE RESISTANCE (Ω)
OUTPUT SOURCE RESISTANCE (Ω)
100
70
50
30
IOUT = 20mA
TA = 25°C
10
1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5 10.5 11.5 12
VIN = 2.5V
80
60
VIN = 5.5V
40
20
0
-40
-20
SUPPLY VOLTAGE (V)
0
20
40
Output Voltage vs. Output Current
80
100
Power Conversion Efficiency vs. Load
100
0
90
-2
-4
-6
-8
-10
Boost Pin = Open
80
POWER EFFICIENCY (%)
Boost Pin = V+
70
60
50
40
30
20
10
-12
0
10
20
30
40
50
60
70
80
0
90 100
1.0
1.5
2.0
3.0
4.5
6.0
7.5
9.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
50.0
55.0
60.0
OUTPUT VOLTAGE VOUT (V)
60
TEMPERATURE (°C)
OUTPUT CURRENT (mA)
LOAD CURRENT (mA)
Supply Current vs. Temperature
200
SUPPLY CURRENT IDD (µA)
175
150
125
VIN = 12.5V
100
75
50
VIN = 5.5V
25
0
-40
-20
0
20
40
60
80
100
TEMPERATURE (°C)
4-50
TELCOM SEMICONDUCTOR, INC.