TC7660SCOA Microchip Technology, TC7660SCOA Datasheet - Page 6

• Manufacturer Part Number: TC7660SCOA
• Description: IC CHARGE PUMP DC/DC CONV 8-SOIC
• Manufacturer: Microchip Technology
• Type: Switched Capacitor (Charge Pump), Invertingr

Specifications of TC7660SCOA

• Package / Case: 8-SOIC (3.9mm Width)
• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: -1.5 ~ -12 V
• Current - Output: 20mA
• Frequency - Switching: 10kHz ~ 45kHz
• Voltage - Input: 1.5 ~ 12 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Power - Output: 470mW
• Minimum Operating Temperature: 0 C
• Mounting Style: SMD/SMT
• Function: Inverting/Step Up
• Output Voltage: - 12 V to - 1.5 V or 3 V to 24 V
• Output Current: 20 mA
• Maximum Operating Temperature: + 70 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant
• Other names: 158-1067; 158-1067

TC7660S-14 9/16/96
TC7660S
Combined Negative Voltage Conversion
and Positive Supply Multiplication
8 to provide negative voltage conversion and positive volt-
age multiplication simultaneously. This approach would be,
for example, suitable for generating +9V and – 5V from an
existing +5V supply. In this instance, capacitors C
perform the pump and reservoir functions, respectively, for
the generation of the negative voltage, while capacitors C
and C
plied 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
eration are bidirectional, the charge transfer can be per-
formed 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 switch-
drive 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
C 1
Figure 9 combines the functions shown in Figures 3 and
Since the switches that allow the charge pumping op-
+
4
are pump and reservoir, respectively, for the multi-
1
2
3
4
Figure 7. Lowering Oscillator Frequency
1
2
3
4
TC7660S
Figure 8. Positive Voltage Multiplier
TC7660S
8
7
6
5
8
7
6
5
D 1
+
V +
C 1
D 2
+
+
V OUT =
(2 V + ) – (2 V F )
C 2
C 2
V
C OSC
1
+
V OUT
and C
3
2
6
will bypass the other (D
on), or else the diode and resistor shown dotted in Figure 10
can be used to "force" the internal regulator on.
Voltage Splitting
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 (~250 ).
Negative Voltage Generation for
Display ADCs
a fixed power supply system, the TC7106 will perform
conversions with input signal referenced to power supply
ground.
Negative Supply Generation for
4
supplies. The TC7660S provides an inexpensive –5V source.
(See AN16 and AN17 for TC7135 interface details and
software routines.)
Figure 9. Combined Negative Converter and Positive Multiplier
+
C 1
The same bidirectional characteristics used in Figure 10
The TC7106 is designed to work from a 9V battery. With
The TC7135 is a 4
Digit Data Acquisition System
SUPER CHARGE PUMP DC-TO-DC
1
2
3
4
TC7660S
C 2
+
VOLTAGE CONVERTER
1
and D
8
7
6
5
digit ADC operating from 5V
© 2001 Microchip Technology Inc.
2
V +
in Figure 9 would never turn
D 1
D 2
V OUT =
(2 V + ) – (2 V F )
+
+
V OUT = –V +
C 3
C 4
DS21467A