TC682 TELCOM [TelCom Semiconductor, Inc], TC682 Datasheet - Page 3

• Manufacturer Part Number: TC682
• Description: INVERTING VOLTAGE DOUBLER
• Manufacturer: TELCOM [TelCom Semiconductor, Inc]

INVERTING VOLTAGE DOUBLER
Phase 2
negative terminal of C
capacitor C
transferring the generated – 10V to C
positive side of capacitor C
negative side is connected to ground. C
V
MAXIMUM OPERATING LIMITS
approximately 5.8V, and V
maximum supply voltage or excessive current will be shunted
by these diodes, potentially damaging the chip. The TC682
will operate over the entire operating temperature range with
an input voltage of 2V to 5.5V.
DETAILED DESCRIPTION
Phase 1
cycle, capacitor C
switched to ground and the charge in C
. Since C
C
CC
2
is now –10V.
V
The TC682 has on-chip zener diodes that clamp V
V
and GND and Phase 1 begins again.
TELCOM SEMICONDUCTOR, INC.
SS
SS
transfer – phase two of the clock connects the
charge storage – before this phase of the clock
+
2
is at +5V, the voltage potential across capacitor
3
+
–
+
–
and the positive terminal of C
SW2
SW1
Figure 3. Charge Pump – Phase 2
Figure 2. Charge Pump – Phase 1
SW2
SW1
C
C
1
1
–5V
1
is already charged to +5V. C
SW4
2
–
+
+
–
to the negative side of reservoir
SW3
–
OUT
SW4
C
SW3
–10V
C
1
2
2
to – 11.6V. Never exceed the
is switched to +5V and the
+5V
V
IN
= +5V
3
. Simultaneously, the
+
–
1
+
–
–
2
C
C
is transferred to C
is then switched to
3
3
V
V
OUT
OUT
2
to ground,
1
+
is then
IN
to
2
–
EFFICIENCY CONSIDERATIONS
approach 100% efficiency under the following conditions:
V
C
loads.
output ripple. Larger values of both pump and reservoir
capacitors improve the efficiency. See "Capacitor Selec-
tion" in Applications section.
APPLICATIONS
Negative Doubling Converter
charge pump voltage converter which provides a negative
output of two times a positive input voltage (Figure 4).
–
OUT
1
C
C
1
2
and C
Theoretically a charge pump voltage multiplier can
• The charge pump switches have virtually no offset
• Minimal power is consumed by the drive circuitry
• The impedances of the reservoir and pump capaci-
For the TC682, efficiency is as shown below:
Voltage Efficiency = V
Power Loss
There will be a substantial voltage difference between
Larger values of reservoir capacitor C
The most common application of the TC682 is as a
and 2 V
and are extremely low on resistance.
tors are negligible.
22 F
22 F
2
are high with respect to their respective output
IN
Figure 4. Inverting Voltage Doubler
if the impedances of the pump capacitors
1
2
3
4
C
C
V
C
2
1
2
OUT
–
–
–
+
TC682
= I
V
V
OUT
OUT
DROP
OUT
GND
C
V
1
(V
IN
+
= – 2V
/ (– 2V
= (I
DROP
7
6
5
OUT
)
IN
IN
) (R
)
+ V
22 F
C
OUT
DROP
3
3
)
will reduce
TC682
V
V
GND
4-23
OUT
IN
–
1
2
3
4
5
6
7
8