+5V TO
±
10V VOLTAGE CONVERTER
1
TCM680
V
IN
= +5V
–
+
SW1
+
–
+
C
1
SW2
–5V
–
C
2
SW4
–
+
C
3
SW3
C
4
V
DD
V
SS
DETAILED DESCRIPTION
Phase 1
V
SS
charge storage – The positive side of capacitors C
1
+
and C
2
are connected to +5V at the start of this phase. C
1
is
–
then switched to ground and the charge in C
1
is transferred
–
+
to C
2
. Since C
2
is connected to +5V, the voltage potential
across capacitor C
2
is now 10V.
V
IN
= +5V
–
+
SW1
+
–
+
C
1
SW2
–5V
–
C
2
SW4
–
+
C
3
SW3
2
3
4
5
6
7
Figure 4. Charge Pump – Phase 3
C
4
V
DD
V
SS
Phase 4
V
DD
transfer – The fourth phase of the clock connects
the negative terminal of C
2
to ground, and transfers the
generated 10V across C
2
to C
4
, the V
DD
storage capacitor.
Again, simultaneously with this, the positive side of capaci-
tor C
1
is switched to +5V and the negative side is connected
to ground, and the cycle begins again.
+5V
–
SW1
+
–
C
1
SW2
SW3
+
–
SW4
–10V
C
2
+
C
4
V
DD
V
SS
–
+
C
3
Figure 2. Charge Pump – Phase 1
Phase 2
V
SS
transfer – Phase two of the clock connects the
negative terminal of C
2
to the V
SS
storage capacitor C
3
and
the positive terminal of C
2
to ground, transferring the gener-
ated –10V to C
3
. Simultaneously, the positive side of capaci-
tor C
1
is switched to +5V and the negative side is connected
to ground.
+5V
Figure 5. Charge Pump – Phase 4
–
SW1
+
–
C
1
SW2
+
–
SW4
–10V
SW3
C
2
+
C
4
V
DD
V
SS
–
+
C
3
MAXIMUM OPERATING LIMITS
The TCM680 has on-chip zener diodes that clamp V
IN
+
–
to 5.8V, V
OUT
to 11.6V, and V
OUT
to –11.6V. Never exceed
the maximum supply voltage or excessive current will be
shunted by these diodes, potentially damaging the chip. The
TCM680 will operate over the entire operating temperature
range with an input voltage of 2V to 5.5V.
Figure 3. Charge Pump – Phase 2
Phase 3
V
DD
charge storage – The third phase of the clock is
identical to the first phase – the charge transferred in C
1
produces –5V in the negative terminal of C
1
, which is applied
+
to the negative side of capacitor C
2
. Since C
2
is at +5V, the
voltage potential across C
2
is 10V.
8
4-15
TELCOM SEMICONDUCTOR, INC.
TELCOM [ TELCOM SEMICONDUCTOR, INC ]
