ICL7660CSA Maxim Integrated Products, ICL7660CSA Datasheet - Page 6

• Manufacturer Part Number: ICL7660CSA
• Description: IC VOLT CONV CMOS SW-CAP 8-SOIC
• Manufacturer: Maxim Integrated Products
• Type: Switched Capacitor (Charge Pump), Divider, Doubler, Invertingr

Specifications of ICL7660CSA

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Current - Output: 20mA
• Frequency - Switching: 10kHz
• Voltage - Input: 1.5 ~ 10 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Power - Output: 471mW
• Function: Inverting, Step Up
• Output Voltage: - 1.5 V to - 10 V, 3 V to 20 V
• Output Current: 20 mA
• Maximum Operating Temperature: + 70 C
• Minimum Operating Temperature: 0 C
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Voltage - Output: -

Switched-Capacitor Voltage Converters
Figure 2. Ideal Voltage Inverter
6
Figure 3a. Switched Capacitor Model
Figure 3b. Equivalent Circuit
_______________________________________________________________________________________
V+
V+
V+
R
C1
S3
S1
EQUIV
R
EQUIV
f
=
C1
f C1
1
S4
S2
C2
C2
C2
R
LOAD
R
V
LOAD
OUT
V
OUT
V
OUT
= -(V+)
current is: I = f x ∆Q = f x C1(V+ - V
equation in Ohm’s law form defines an equivalent resis-
tance synthesized by the switched-capacitor circuit
where:
where f is one-half the oscillator frequency. This resis-
tance is a major component of the output impedance of
switched-capacitor circuits like the MAX1044/ICL7660.
As shown in Figure 4, the MAX1044/ICL7660 contain
MOSFET switches, the necessary transistor drive cir-
cuitry, and a timing oscillator.
The MAX1044/ICL7660 are designed to provide a
simple, compact, low-cost solution where negative or
doubled supply voltages are needed for a few low-
power components. Figure 5 shows the basic negative
voltage converter circuit. For many applications, only
two external capacitors are needed. The type of
capacitor used is not critical.
Figure 4 shows an internal voltage regulator inside the
MAX1044/ICL7660. Use the LV pin to bypass this
regulator, in order to improve low-voltage performance
Figure 4. MAX1044 and ICL7660 Functional Diagram
________________Design Information
BOOST
pin 1
pin 7
OSC
Proper Use of the Low-Voltage (LV) Pin
1M
pin 6
LV
I
R
÷ 2
EQUIV
(V+ - V
Q
1 / (f x C1)
Q
and
f x C1
OUT
1
pin 8
pin 3
GND
V+
)
S1
S3
OUT
CAP+
pin 2
CAP-
pin 4
). Rewriting this
S4
S2
V
pin 5
OUT