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CAT660EVA Schematic ( PDF Datasheet ) - Catalyst Semiconductor

Teilenummer CAT660EVA
Beschreibung 100mA CMOS Charge Pump Inverter/Doubler
Hersteller Catalyst Semiconductor
Logo Catalyst Semiconductor Logo 




Gesamt 16 Seiten
CAT660EVA Datasheet, Funktion
Preliminary Information
CAT660
100mA CMOS Charge Pump Inverter/Doubler
FEATURES
ALOGEN FR
LEA D F REETM
I Replaces MAX660 and LTC®660
I Converts V+ to V- or V+ to 2V+
I Low output resistance, 4typical
I High power efficiency
I Selectable charge pump frequency
- 10kHz or 80kHz
- Optimize capacitor size
I Low quiescent current
I Pin-compatible, high-current alternative to
7660/1044
I Industrial temperature range
I Available in 8-pin SOIC, DIP and 0.8mm thin 8-
pad TDFN packages
- Lead-free, halogen-free package option
APPLICATIONS
I Negative voltage generator
I Voltage doubler
I Voltage splitter
I Low EMI power source
I GaAs FET biasing
I Lithium battery power supply
I Instrumentation
I LCD contrast bias
I Cellular phones, pagers
DESCRIPTION
The CAT660 is a charge-pump voltage converter. It will
invert a 1.5V to 5.5V input to a -1.5V to -5.5V output. Only
two external capacitors are needed. With a guaranteed
100mA output current capability, the CAT660 can replace
a switching regulator and its inductor. Lower EMI is
achieved due to the absence of an inductor.
In addition, the CAT660 can double a voltage supplied
from a battery or power supply. Inputs from 2.5V to 5.5V
will yield a doubled, 5V to 11V output voltage.
A Frequency Control pin (BOOST/FC) is provided to
select either a high (80kHz) or low (10kHz) internal
oscillator frequency, thus allowing quiescent current vs.
capacitor size trade-offs to be made. The 80kHz
frequency is selected when the FC pin is connected to
V+. The operating frequency can also be adjusted with
an external capacitor at the OSC pin or by driving OSC
with an external clock.
Both 8-pin DIP and SOIC packages are available in the
industrial temperature range. The TDFN package has a
4x4mm footprint and features a 0.8mm maximum height.
Compared to the 8-pin SOIC the TDFN package footprint
is nearly 50% less. For die availability, contact Catalyst
Semiconductor marketing.
The CAT660 replaces the MAX660 and the LTC660.
In addition, the CAT660 is pin compatible with the 7660/
1044, offering an easy upgrade for applications with
100mA loads.
TYPICAL APPLICATION
+VIN
1.5V to 5.5V
C1
+
1 BOOST/FC
V+ 8
2 CAP+
CAT660
3 GND
OSC 7
LV 6
4 CAP-
OUT 5
VOLTAGE INVERTER
Inverted
Negative
Output
Voltage
C1 +
VIN = 2.5V to 5.5V
1 BOOST/FC
V+ 8
2 CAP+
OSC 7
CAT660
3 GND
LV 6
4 CAP-
OUT 5
POSITIVE
VOLTAGE DOUBLER
Doubled
Positive
Output
Voltage
© 2005 by Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
1
Doc. No. 5000, Rev. U






CAT660EVA Datasheet, Funktion
CAT660
APPLICATION INFORMATION
Circuit Description and Operating Theory
The CAT660 switches capacitors to invert or double an
input voltage.
Figure 2 shows a simple switch capacitor circuit. In
position 1 capacitor C1 is charged to voltage V1. The
total charge on C1 is Q1 = C1V1. When the switch
moves to position 2, the input capacitor C1 is discharged
to voltage V2. After discharge, the charge on C1 is Q2 =
C1V2.
The charge transferred is:
Q = Q1 - Q2 = C1 × (V1 - V2)
If the switch is cycled "F" times per second, the current
(charge transfer per unit time) is:
I = F × ∆Q = F × C1 (V1 - V2)
Rearranging in terms of impedance:
(V1-V2)
V1-V2
I= =
(1/FC1)
REQ
The 1/FC1 term can be modeled as an equivalent
impedance REQ. A simple equivalent circuit is shown in
figure 3. This circuit does not include the switch
resistance nor does it include output voltage ripple. It
does allow one to understand the switch-capacitor
topology and make prudent engineering tradeoffs.
For example, power conversion efficiency is set by the
output impedance, which consists of REQ and switch
resistance. As switching frequency is decreased, REQ,
the 1/FC1 term, will dominate the output impedance,
causing higher voltage losses and decreased efficiency.
As the frequency is increased quiescent current
increases. At high frequency this current becomes
significant and the power efficiency degrades.
The oscillator is designed to operate where voltage
losses are a minimum. With external 150µF capacitors,
the internal switch resistances and the Equivalent Series
Resistance (ESR) of the external capacitors determine
the effective output impedance.
A block diagram of the CAT660 is shown in figure 4. The
CAT660 is a replacement for the MAX660 and the
LTC660.
Figure 2. Switched-Capacitor Building Block
V1 V2
C1 C2 RL
Figure 3. Switched-Capacitor Equivalent Circuit
REQ
V1
V2
REQ = 1
FC1
C2 RL
Doc. No. 5000, Rev. U
6

6 Page









CAT660EVA pdf, datenblatt
CAT660
CASCADE OPERATION FOR HIGHER NEGATIVE VOLTAGES
The CAT660 can be cascaded as shown in figure 11 to generate more negative voltage levels. The output resistance
is approximately the sum of the individual CAT660 output resistance.
VOUT= -N x VIN, where N represents the number of cascaded devices.
+
C1
+VIN
88
2 CAT660
3 "1"
+
C1
2 CAT660
3 "N"
4
54
5
VOUT = -NVIN
+ C2
+ C2
Figure 11: Cascading to Increase Output Voltage
PARALLEL OPERATION
Paralleling CAT660 devices will lower output resistance. As shown in figure 12, each device requires its own pump
capacitor, C2, but the output reservoir capacitor is shared with all devices. The value of C2 should be increased by
a factor of N, where N is the number of devices.
The output impedance of the combined CAT660's is:
ROUT(Of "N" CAT660s)= ROUT (Of the CAT660)
N (Number of devices)
+
C1
+VIN
8
2 CAT660
3 "1"
+
C1
45
8
2 CAT660
3 "N"
45
Doc. No. 5000, Rev. U
C2
+
Figure 12: Paralleling Devices Reduce Output Resistance
12

12 Page





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