7

Date: 5/25/04

SP6680 High Efficiency Buck/Boost Charge Pump Regulator

© Copyright 2004 Sipex Corporation

Figure 3. Typical SIM Card Application Circuit for the SP6680

Any standard CMOS logic output is suitable for

driving the C/4 or Cx8 control lines as long as

logic low is less than 0.4V and logic high is

greater than 1.3V.

Efficiency

Power efficiency with the SP6680 charge pump

regulator is improved over standard charge pumps

doubler circuits by the inclusion of an 1.5X

output mode, as described in the Theory of

Operation section. The net result is an increase

in efficiency at battery inputs greater than 3.7 to

3.8V where the SP6680 switches to the 1.5X

mode. This is illustrated in figure 4 Efficiency vs

Input Voltage.

Capacitor Selection

In order to maintain the lowest output resistance,

input ripple voltage and output ripple voltage,

multi-layer ceramic capacitors with inherently

low ESR are recommended. Refer to Table 2 for

some suggested low ESR capacitors. Tables of

output resistance and ripple voltages for a vari-

ety of input, output and pump capacitors are

included here to use as a guide in capacitor

selection. Measured conditions are with CLK =

32kHz, 5mA output load and all capacitors are

2.2uF except when stated otherwise. A DC

power supply with added 0.25ohm output ESR

was used to simulate a Lithium Ion Battery as

shown in figure 5.

Figure 4. Efficiency vs Battery Voltage

Figure 5. Capacitor Selection Test Circuit

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SP6680 Efficiency vs Battery Voltage

50

60

70

80

90

100

3.0

3.3

3.6

3.9

4.2

Battery Voltage (V)

8.192kHz, Iout = 2mA

32.768kHz, Iout = 10mA

262.14kHz, Iout = 40mA

Table 1. Control Line Logic for the Internal Charge

Pump Oscillator

V

C/4

Cx8

CLK

GND

SP6680

8

CF1P

CF1N

CF2P

CF2N

4.7µF

2.2µF

2.2µF

2

9

10

7

1

6

45

3

+3.6V

Lithium-Ion

Battery

LDO

+5.0V output

V

IN

2.2µF

2.2µF

Power Supply

HP3631A

1000µF

0.25ohm

0.75” Leads

SP6680 EvBd

2.2µF Caps

+

-