TC660 TELCOM [TelCom Semiconductor, Inc], TC660 Datasheet - Page 6

• Manufacturer Part Number: TC660
• Description: 100mA CHARGE PUMP DC-TO-DC VOLTAGE CONVERTER
• Manufacturer: TELCOM [TelCom Semiconductor, Inc]

4-10
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 +5.5V, keeping in mind that
pin 6 (LV) is tied to the supply negative (GND) only for supply
voltages below 3.0V.
TC660
voltages greater than 3.0V.
and for more than 10 sec (a very slow startup!) in
doubler mode.
the + terminal of C
TC660 and the + terminal of C
GND.
150 µF
Figure 3 shows typical connections to provide a nega-
C 1
*
NOTES:
C 1
+
Figure 3. Simple Negative Converter
1. V OUT = –V + for 1.5V
1
2
3
4
1
2
3
4
TC660
1
must be connected to pin 2 of the
TC660
"1"
8
7
6
5
V
2
+
must be connected to
V +
8
7
6
5
+
Figure 4. Paralleling Devices Lowers Output Impedance
in inverting mode
5.5V
V
+
+
150 µF
C 2
V OUT
*
C 1
those of a nearly ideal voltage source in series with 6.5 .
Thus, for a load current of –100mA and a supply voltage of
+5V, the output voltage would be – 4.35V.
primarily, to capacitive reactance of the charge transfer
capacitor (C
output for only 1/2 of the cycle, the equation is:
Paralleling Devices
leled to reduce output resistance (Figure 4). The reservoir
capacitor, C
its own pump capacitor, C
would be approximately:
where f = 10 kHz and C
The output characteristics of the circuit in Figure 3 are
The dynamic output impedance of the TC660 is due,
Any number of TC660 voltage converters may be paral-
1
2
3
4
100mA CHARGE PUMP DC-TO-DC
TC660
"n"
2
1
, serves all devices, while each device requires
R
). Since this capacitor is connected to the
OUT
=
X
8
7
6
5
C
TELCOM SEMICONDUCTOR, INC.
=
n (number of devices)
VOLTAGE CONVERTER
1
R
2 f C
= 150 F.
1
. The resultant output resistance
OUT
2
1
(of TC660)
= 0.21
+
C 2
R L