tc7660s Microchip Technology Inc., tc7660s Datasheet - Page 4

• Manufacturer Part Number: tc7660s
• Description: Super Charge Pump Dc-to-dc Voltage Converter
• Manufacturer: Microchip Technology Inc.

TC7660S-14 9/16/96
TC7660S
Dos and Don'ts
• Do not exceed maximum supply voltages.
• Do not connect the LV terminal to GND for supply
• Do not short circuit the output to V
• When using polarized capacitors in the inverting mode,
Simple Negative Voltage Converter
tive 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.
10 F
voltages greater than 3.5V.
above 5.5V for extended periods; however, transient
conditions including start-up are okay.
the + terminal of C
TC7660S and the + terminal of C
to GND.
C 1
Figure 3 shows typical connections to provide a nega-
*
NOTES:
C 1
+
Figure 3. Simple Negative Converter
1
2
3
4
1
2
3
4
TC7660S
TC7660S
1
must be connected to pin 2 of the
"1"
8
7
6
5
8
7
6
5
V
+
2
Figure 4. Paralleling Devices Lowers Output Impedance
+
must be connected
V +
supply for voltages
+
C 2
10 F
V OUT
C 1
*
4
those of a nearly ideal voltage source in series with 70 .
Thus, for a load current of –10mA and a supply voltage of
+5V, the output voltage would be – 4.3V.
primarily, to capacitive reactance of the charge transfer
capacitor (C
output for only 1/2 of the cycle, the equation is:
where f = 10kHz and C
Paralleling Devices
paralleled to reduce output resistance (Figure 4). The reser-
voir capacitor, C
requires its own pump capacitor, C
resistance would be approximately:
1
2
3
4
The output characteristics of the circuit in Figure 3 are
The dynamic output impedance of the TC7660S is due,
Any number of TC7660S voltage converters may be
TC7660S
SUPER CHARGE PUMP DC-TO-DC
"n"
R
OUT
1
). Since this capacitor is connected to the
=
8
7
6
5
2
, serves all devices, while each device
n (number of devices)
X
R
C
OUT
=
VOLTAGE CONVERTER
1
= 10 F.
2 f C
(of TC7660S)
2
© 2001 Microchip Technology Inc.
1
+
= 3.18
C 2
1
R L
. The resultant output
DS21467A