MAX660M/NOPB National Semiconductor, MAX660M/NOPB Datasheet - Page 5

• Manufacturer Part Number: MAX660M/NOPB
• Description: IC CONVERTER SWITCH CAP 8-SOIC
• Manufacturer: National Semiconductor
• Type: Switched Capacitor (Charge Pump), Doubler, Invertingr

Specifications of MAX660M/NOPB

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: -1.5 ~ -5.5 V, 3 ~ 11 V
• Current - Output: 100mA
• Frequency - Switching: 10kHz, 80kHz
• Voltage - Input: 1.5 ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Power - Output: 735mW
• Dc: 1152
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: *MAX660M; *MAX660M/NOPB; MAX660M

Pin
1
2
3
4
5
6
7
8
Pin Description
Circuit Description
The MAX660 contains four large CMOS switches which are
switched in a sequence to invert the input supply voltage.
Energy transfer and storage are provided by external capaci-
tors. Figure 2 illustrates the voltage conversion scheme.
When S
age V+. During this time interval switches S
open. In the second time interval, S
and S
cycles, the voltage across C
the anode of C
cathode of C
in the switches, and no ESR in the capacitors. In reality, the
charge transfer efficiency depends on the switching fre-
quency, the on-resistance of the switches, and the ESR of
the capacitors.
4
Name
CAP+
CAP−
GND
OSC
OUT
FC
V+
1
LV
are closed, C
FIGURE 2. Voltage Inverting Principle
and S
2
equals −(V+) assuming no load on C
2
3
is connected to ground, the output at the
are closed, C
Frequency control for internal oscillator:
FC = open, f
FC = V+, f
FC has no effect when OSC pin is driven externally.
Connect this pin to the positive terminal of
charge-pump capacitor.
Power supply ground input.
Connect this pin to the negative terminal of
charge-pump capacitor.
Negative voltage output.
Low-voltage operation input. Tie LV to GND when
input voltage is less than 3.5V. Above 3.5V, LV can
be connected to GND or left open. When driving
OSC with an external clock, LV must be connected
to GND.
Oscillator control input. OSC is connected to an
internal 15 pF capacitor. An external capacitor can
be connected to slow the oscillator. Also, an
external clock can be used to drive OSC.
Power supply positive voltage input.
1
is charging C
2
OSC
will be pumped to V+. Since
1
OSC
charges to the supply volt-
= 80 kHz (typ);
1
= 10 kHz (typ);
and S
Voltage Inverter
2
. After a number of
3
are open and S
2
and S
2
, no loss
DS100898-21
4
are
2
5
Application Information
SIMPLE NEGATIVE VOLTAGE CONVERTER
The main application of MAX660 is to generate a negative
supply voltage. The voltage inverter circuit uses only two ex-
ternal capacitors as shown in the Typical Application Circuits.
The range of the input supply voltage is 1.5V to 5.5V. For a
supply voltage less than 3.5V, the LV pin must be connected
to ground to bypass the internal regulator circuitry. This gives
the best performance in low voltage applications. If the sup-
ply voltage is greater than 3.5V, LV may be connected to
ground or left open. The choice of leaving LV open simplifies
the direct substitution of the MAX660 for the LMC7660
Switched Capacitor Voltage Converter.
The output characteristics of this circuit can be approximated
by an ideal voltage source in series with a resistor. The volt-
age source equals −(V+). The output resistance R
function of the ON resistance of the internal MOS switches,
the oscillator frequency, and the capacitance and ESR of C
and C
where R
MOS switches shown in Figure 2 .
High value, low ESR capacitors will reduce the output resis-
tance. Instead of increasing the capacitance, the oscillator
frequency can be increased to reduce the 2/(f
Once this term is trivial compared with R
ther increasing in oscillator frequency and capacitance will
become ineffective.
The peak-to-peak output voltage ripple is determined by the
oscillator frequency, and the capacitance and ESR of the
output capacitor C
Function
2
. A good approximation is:
Same as inverter.
Same as inverter.
Power supply positive voltage input.
Same as inverter.
Power supply ground input.
LV must be tied to OUT.
Same as inverter except that OSC cannot be driven
by an external clock.
Positive voltage output.
SW
is the sum of the ON resistance of the internal
2
:
Voltage Doubler
SW
and ESRs, fur-
osc
www.national.com
x C
1
out
) term.
is a
1