CAT661EVA-GT3 ON Semiconductor, CAT661EVA-GT3 Datasheet - Page 7

• Manufacturer Part Number: CAT661EVA-GT3
• Description: Charge Pumps CHG PUMP VOLT CONVERTER
• Manufacturer: ON Semiconductor

Specifications of CAT661EVA-GT3

• Rohs: yes
• Function: Inverting
• Output Voltage: 5 V to 11 V
• Output Current: 100 mA
• Supply Current: 0.5 mA
• Maximum Operating Temperature: + 105 C
• Package / Case: SOIC-8
• Input Voltage: 2.5 V to 5.5 V
• Maximum Power Dissipation: 500 mW
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT
• Switching Frequency: 12.5 KHz

Application Information
Circuit Description and Operating Theory
input voltage.
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.
(charge transfer per unit time) is:
impedance REQ. A simple equivalent circuit is shown in
The CAT661 switches capacitors to invert or double an
Figure 19 shows a simple switch capacitor circuit. In
The charge transferred is:
If the switch is cycled “F” times per second, the current
Rearranging in terms of impedance:
The 1/FC1 term can be modeled as an equivalent
Figure 19. Switched−Capacitor Building Block
V1
DQ + Q1 * Q2 + C1
I + F
I +
(V1 * V2)
DQ + F
(1 FC1)
C1
+ V1 * V2
C1 (V1 * V2)
C2
REQ
(V1 * V2)
R
L
V2
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Figure 20. 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.
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.
are a minimum. With external 150 mF capacitors, the internal
switch resistances and the Equivalent Series Resistance
(ESR) of the external capacitors determine the effective
output impedance.
Figure 20. Switched−Capacitor Equivalent Circuit
For example, power conversion efficiency is set by the
The oscillator is designed to operate where voltage losses
A block diagram of the CAT661 is shown in Figure 21.
V1
REQ + 1
FC1
REQ
C2
R
L
V2