Microchip Technology TC7660HEPA, TC7660HEOA, TC7660HCPA, TC7660HCOA Datasheet

EVALUATION
KIT
AVAILABLE
HIGH FREQUENCY 7660 DC-TO-DC VOLTAGE CONVERTER
G
TC7660H
Pin Compatible with 7660, High Frequency
Performance DC-to-DC Converter
Low Cost, Two Low Value External Capacitors
Required ........................................................ (1.0µF)
Converts +5V Logic Supply to ±5V System
Wide Input Voltage Range .................... 1.5V to 10V
Voltage Conversion........................................99.7%
Power Efficiency................................................85%
Available in 8-Pin SOIC and 8-Pin PDIP Packages
PIN CONFIGURATION (DIP and SOIC)
NC
CAP
ND
CAP
CAP
GND
CAP
NC
1
+
2
TC7660HCPA
3 4
1 2 3 4
TC7660HEPA
TC7660HCOA TC7660HEOA
+
+
8
V
OSC
7
LOW
6
VOLTAGE (LV)
V
5
OUT
+
V
8
OSC
7
LOW
6
VOLTAGE (LV)
5
V
OUT
GENERAL DESCRIPTION
The TC7660H is a pin-compatible, high frequency up­grade to the Industry standard TC7660 charge pump volt­age converter. It converts a +1.5V to +10V input to a corresponding – 1.5V to – 10V output using only two low­cost capacitors, eliminating inductors and their associated cost, size and EMI.
The TC7660H operates at a frequency of 120kHz (versus 10kHz for the TC7660), allowing the use of 1.0µF external capacitors. Oscillator frequency can be reduced (for lower supply current applications) by connecting an external capacitor from OSC to ground.
The TC7660H is available in 8-pin DIP and small outline (SOIC) packages in commercial and extended temperature ranges.
ORDERING INFORMATION
Temperature
Part No. Package Range
TC7660HCOA 8-Pin SOIC 0°C to +70°C TC7660HCPA 8-Pin Plastic DIP 0°C to +70°C TC7660HEOA 8-Pin SOIC – 40°C to +85°C TC7660HEPA 8-Pin Plastic DIP – 40°C to +85°C
TC7660EV Evaluation Kit for
Charge Pump Family
NC = NO INTERNAL CONNECTION
FUNCTIONAL BLOCK DIAGRAM
OSC
LV
© 2001 Microchip Technology Inc. DS21466A
7
OSCILLATOR
6
TC7660H
RC
INTERNAL
VOLTAGE
REGULATOR
÷ 2
VOLTAGE–
LEVEL
TRANSLATOR
V+CAP
82
3
GND
+
LOGIC
NETWORK
4
5
CAP
V
OUT
TC7660H-2 10/1/96
TC7660H
HIGH FREQUENCY 7660 DC-TO-DC
VOLTAGE CONVERTER
ABSOLUTE MAXIMUM RATINGS*
Operating Temperature Range
C Suffix ..................................................0°C to +70°C
Supply Voltage ...................................................... +10.5V
LV and OSC Inputs
Voltage (Note 1) ........................ – 0.3V to (V+ + 0.3V)
E Suffix ............................................ – 40°C to +85°C
Storage Temperature Range ...............– 65°C to +150°C
Lead Temperature (Soldering, 10 sec) .................+300°C
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
5.5V) .........Continuous
SUPPLY
Power Dissipation (TA 70°C) (Note 2)
SOIC...............................................................470mW
Plastic DIP ......................................................730mW
ELECTRICAL CHARACTERISTICS: Over Operating Temperature Range with V
*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.
+
= 5V, CI = C2 = 1µF, C
OSC
= 0,
Test Circuit (Figure 1), unless otherwise indicated.
Symbol Parameter Test Conditions Min Typ Max Unit
+
I
+
V
H
+
V
L
R
OUT
F
OSC
P
EFF
V
EFF
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 = 0.46 1.0 mA Supply Voltage Range, High Min ≤ TA Max, 3 10 V
RL = 5kΩ, LV Open
Supply Voltage Range, Low Min ≤ TA Max, 1.5 3.5 V
RL = 5kΩ, LV to GND
Output Source Resistance I
= 20mA, TA = 25°C 55 80
OUT
I
= 20mA, 0°C ≤ TA +70°C—95
OUT
(C Device) I
= 20mA, – 40°C ≤ TA +85°C 110
OUT
(E Device)
+
V
= 2V, I
= 3mA, LV to GND 150 250
OUT
0°C TA +70°C Oscillator Frequency 120 kHz Power Efficiency I
= 10mA, Min ≤ TA ≤ Max 81 85 %
OUT
Voltage Efficiency RL = 99 99.7 %
inputs from sources operating from external supplies be applied prior to "power up" of the TC7660H.
2. Derate linearly above 50°C by 5.5mW/°C.
TC7660H-2 10/1/96
2
© 2001 Microchip Technology Inc. DS21466A
HIGH FREQUENCY 7660 DC-TO-DC VOLTAGE CONVERTER
I
S
+
V
(+5V)
2
R
L
C
1.0 µF
1 2
+
1
TC7660H
3 4
Figure 1. TC7660H Test Circuit
8 7 6 5
C
1.0 µF
+
Detailed Description
The TC7660H contains all the necessary circuitry to implement a voltage inverter, with the exception of two external capacitors, which may be inexpensive 1.0µF non-polarized 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.
TC7660H
To improve low-voltage operation, the LV pin should be connected to GND. 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 capacitative 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.
(3) The impedances of the pump and reservoir
capacitors are negligible at the pump frequency.
The TC7660H 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:
2
E = 1/2 C1 (V
1
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 1), compared to the value of RL, there will be a substantial difference in voltages V1 and V2. Therefore, it is not only desirable 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.
Do's and Don'ts
• Do not exceed maximum supply voltages.
– V
2
)
2
S
+
V
GND
Figure 2. Idealized Charge Pump Inverter
© 2001 Microchip Technology Inc. DS21466A
1
S
3
• Do not connect LV terminal to GND for supply voltages
S
2
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.
C
S
2
4
V
OUT
= – V
IN
• When using polarized capacitors in the inverting mode,
the + terminal of C1 must be connected to pin 2 of the TC7660H and the + terminal of C2 must be connected to GND Pin 3.
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TC7660H-2 10/1/96
TC7660H
HIGH FREQUENCY 7660 DC-TO-DC
VOLTAGE CONVERTER
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 +10V, keeping in mind that pin 6 (LV) is tied to the supply negative (GND) only for supply voltages below 3.5V.
The output characteristics of the circuit in Figure 3 are those of a nearly idea l voltage source in series with 70Ω. Thus, for a load current of – 10 mA and a supply voltage of +5V, the output voltage would be – 4.3V.
The dynamic output impedance of the TC7660H 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:
XC = = 2.12Ω,
where f = 150kHz and C1 = 1.0µF.
2
2πf C
1
+
V
+
V
C
1.0 µF
*
1 2
+
1
TC7660H
3 4
1. V
Figure 3. Simple Negative Converter
OUT
= –n V+for 1.5V V+ 10VNOTES:
8 7 6 5
V
*
OUT
C
2
1.0 µF
+
Paralleling Devices
Any number of TC7660H 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 TC7660H)
R
OUT
=
OUT
n (number of devices)
1.0 µF
NOTES:
*
1. V
OUT
1 2
+
= –n V+for 1.5V V 10V
TC7660H
3 4
"1"
8 7 6 5
+
Figure 4. Increased Output Voltage by Cascading Devices
1.0 µF
Cascading Devices
The TC7660H may be cascaded as shown in (Figure 4) to produce larger negative multiplication of the initial supply voltage. However, due to the finite efficiency of each device, the practical limit is probably 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 TC7660H R
values.
OUT
TC7660H-2 10/1/96
1 2
+
3 4
TC7660H
"n"
8 7 6 5
1.0 µF
+
V
OUT
*
Changing the TC7660H Oscillator Frequency
It may be desirable in some applications (due to noise or other considerations) to increase or decease the oscillator frequency. This can be achieved by overdriving the oscilla­tor from an external clock, as shown in Figure 6. In order to prevent possible device latch-up, a 1k resistor must be used in series with the clock output. In a situation where the designer has generated the external clock frequency using TTL logic, the addition of a 10k pull-up 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.
4
© 2001 Microchip Technology Inc. DS21466A
HIGH FREQUENCY 7660 DC-TO-DC
C
S
1 2 3 4
8 7 6 5
+
V
+
V
OUT
=
(2 V+) – (2 VF)
C
1
D
1
+
+
C
3
C
4
V
OUT
=
–(V+–VF)
C
2
TC7660H
D
2
+
VOLTAGE CONVERTER
+
V
1
8
TC7660H
1.0 µF
2
C
1
1 2
+
3 4
TC7660H
3
"1"
4
TC7660H
Figure 6. External Clocking
7 6 5
Figure 5. Paralleling Devices Lowers Output Impedance
+
V
8
1 k
7 6 5
V
1.0 µF
+
+
CMO GATE
V
OUT
C
1
1 2
TC7660H
3 4
Combined Negative Voltage Conversion and Positive Supply Multiplication
Figure 8 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 multi-
"n"
8
R
7 6 5
L
+
3
2
plied positive voltage. There is a penalty in this configuration
Positive Voltage Multiplication
The TC7660H may be employed to achieve positive voltage multiplication using the circuit shown in Figure 7. In this application, the pump inverter switches of the TC7660H are used to charge C1 to a voltage level of V+ – VF (where V
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.
+
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 (2 V+) – (2 VF), or twice the supply voltage minus the combined forward voltage drops of diodes D1 and D2.
The source impedance of the output (V
) will depend
OUT
on the output current, but for V+ = 5V and an output current of 10mA, it will be approximately 60Ω.
© 2001 Microchip Technology Inc. DS21466A
1 2
TC7660H
3 4
Figure 7. Positive Voltage Multiplier
8 7 6 5
+
V
D
1
+
C
1
D
2
V
OUT
(2 V+) – (2 VF)
+
C
=
2
Figure 8. Combined Negative Converter and Positive Multiplier
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TC7660H-2 10/1/96
TC7660H
HIGH FREQUENCY 7660 DC-TO-DC
VOLTAGE CONVERTER
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 9 shows a TC7660H 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
C
1.0 µF
1
1 2
+
3 4
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 diode and resistor shown dotted in Figure 9.
Figure 9. Positive Voltage Conversion
TYPICAL PERFORMANCE CHARACTERISTICS (Circuit of Figure 1)
Output Source Resistance vs. Supply Voltage
10k
1k
TA = +25°C
Output Source Resistance vs. Temperature
500
I
= 1 mA
OUT
450
400
200
TC7660H
1 M
= –V
V
INPUT
+
1.0 µF
V
OUT
8 7 6 5
100
OUTPUT SOURCE RESISTANCE (Ω)
10
OUTPUT VOLTAGE (V)
–10
TC7660H-2 10/1/96
6543210
SUPPLY VOLTAGE (V) TEMPERATURE (°C)
Output Voltage vs. Output Current
µF
=1
C
I C2
0
123
45
67
89
10 20 30 40 50 60 70 80 90 100
0
OUTPUT CURRENT (mA)
TA = +25°C LV OPEN
78
150
V+ = +2V
100
V + = +5V
50
OUTPUT SOURCE RESISTANCE (Ω)
0
–55 –25 0 +25 +50 +75 +100 +125
Output Voltage vs. Load Current
5
TA = +25°C
4
V+ = +5V
3 2 1 0
12
OUTPUT VOLTAGE (V)
34
5
10 20 30 40 50 60 70 80
0
6
SLOPE 55
LOAD CURRENT (mA)
© 2001 Microchip Technology Inc. DS21466A
HIGH FREQUENCY 7660 DC-TO-DC VOLTAGE CONVERTER
PACKAGE DIMENSIONS
TC7660H
8-Pin Plastic DIP
.200 (5.08) .140 (3.56)
.150 (3.81) .115 (2.92)
8-Pin SOIC
.045 (1.14) .030 (0.76)
.400 (10.16)
.348 (8.84)
.110 (2.79) .090 (2.29)
.070 (1.78) .040 (1.02)
.022 (0.56) .015 (0.38)
PIN 1
.260 (6.60) .240 (6.10)
.040 (1.02) .020 (0.51)
.015 (0.38) .008 (0.20)
.310 (7.87) .290 (7.37)
3° MIN.
.400 (10.16)
.310 (7.87)
.050 (1.27) TYP.
.197 (5.00) .189 (4.80)
.020 (0.51) .013 (0.33)
.157 (3.99) .150 (3.81)
.010 (0.25) .004 (0.10)
.244 (6.20) .228 (5.79)
.069 (1.75) .053 (1.35)
8° MAX.
.010 (0.25) .007 (0.18)
.050 (1.27) .016 (0.40)
Dimensions: inches (mm)
© 2001 Microchip Technology Inc. DS21466A
7
TC7660H-2 10/1/96
TC7660H
HIGH FREQUENCY 7660 DC-TO-DC
W
ORLDWIDE SALES AND SERVICE
VOLTAGE CONVERTER
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TC7660H-2 10/1/96
8
© 2001 Microchip Technology Inc. DS21466A
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