icl7660aipa Intersil Corporation, icl7660aipa Datasheet - Page 6

• Manufacturer Part Number: icl7660aipa
• Description: Cmos Voltage Converters
• Manufacturer: Intersil Corporation

The voltage regulator portion of the ICL7660 and ICL7660A is
an integral part of the anti-latchup circuitry, however its inherent
voltage drop can degrade operation at low voltages. Therefore,
to improve low voltage operation the “LV” pin should be
connected to GROUND, disabling the regulator. For supply
voltages greater than 3.5V the LV terminal must be left open to
insure latchup proof operation, and prevent device damage.
Theoretical Power Efficiency
Considerations
In theory a voltage converter can approach 100% efficiency
if certain conditions are met.
The ICL7660 and ICL7660A approach these conditions for
negative voltage conversion if large values of C
are used.
V
1. The driver circuitry consumes minimal power.
2. The output switches have extremely low ON resistance
3. The impedances of the pump and reservoir capacitors are
IN
FIGURE 12. IDEALIZED NEGATIVE VOLTAGE CONVERTER
8
and virtually no offset.
negligible at the pump frequency.
10 F
3
+
-
S
S
FIGURE 13A. CONFIGURATION
3
1
7
1
2
3
4
ICL7660A
ICL7660
2
3-31
C
1
8
7
6
5
S
S
10 F
4
2
+
-
V+
FIGURE 13. SIMPLE NEGATIVE CONVERTER
V
OUT
C
1
2
V
and C
OUT
ICL7660, ICL7660A
=
-
3
5
V+
= -V
2
IN
ENERGY IS LOST ONLY IN THE TRANSFER OF
CHARGE BETWEEN CAPACITORS IF A CHANGE IN
VOLTAGE OCCURS. The energy lost is defined by:
E =
where V
transfer cycles. If the impedances of C
high at the pump frequency (refer to Figure 12) compared to
the value of R
voltages V
C
also to employ a correspondingly large value for C
achieve maximum efficiency of operation.
Do’s And Don’ts
1. Do not exceed maximum supply voltages.
2. Do not connect LV terminal to GROUND for supply
3. Do not short circuit the output to V+ supply for supply volt-
4. When using polarized capacitors, the + terminal of C
5. If the voltage supply driving the ICL7660 and ICL7660A
6. User should insure that the output (pin 5) does not go
2
as large as possible to eliminate output voltage ripple, but
voltages greater than 3.5V.
ages above 5.5V for extended periods, however, transient
conditions including start-up are okay.
must be connected to pin 2 of the ICL7660 and ICL7660A
and the + terminal of C
under these conditions. (Anode pin 5, Cathode pin 3).
has a large source impedance (25 - 30 ), then a 2.2 F
capacitor from pin 8 to ground may be required to limit
rate of rise of input voltage to less than 2V/ s.
more positive than GND (pin 3). Device latch up will occur
under these conditions. A 1N914 or similar diode placed
in parallel with C
1
/
2
C
1
1
and V
1
(V
FIGURE 13B. THEVENIN EQUIVALENT
and V
1
L
2
, there will be a substantial difference in the
2
- V
are the voltages on C
2
2
. Therefore it is not only desirable to make
2
2
)
V+
will prevent the device from latching up
+
-
2
R
must be connected to GROUND.
O
V
OUT
1
1
and C
during the pump and
2
are relatively
1
in order to
1