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Date: 5/25/04

SP6680 High Efficiency Buck/Boost Charge Pump Regulator

© Copyright 2004 Sipex Corporation

DESCRIPTION

The SP6680 device is a regulated CMOS charge

pump voltage converter that can be used to

convert a +2.7V to +6.3V input voltage to a

nominal +5.2V to +6.3V output. These devices

are ideal for cellular phone designs involving

battery-powered and/or board level voltage

conversion applications.

An external clock signal with a frequency of

32.768kHz nominal is required for device

operation. A designer can set the SP6680 device

to operate at 3 different charge pump frequencies:

8.192kHz (f

262.14kHz (f

The three frequencies

correspond to three nominal load current ranges:

2mA, 20mA, and 60mA, respectively.

The

SP6680 device optimizes for high power

efficiency with a low quiescent current of 100

µA

at 8.198kHz, 200

µA at 32.768kHz, and 1.0mA

at 262.14kHz. When there is no external clock

signal input, the device is in a low-power

shutdown mode drawing 4.4

µA (typical) current.

The SP6680 device is ideal for designs using

+3.6V lithium ion batteries such as cell phones,

PDAs, medical instruments, and other portable

equipment. For designs involving power sources

above +2.7V up to +6.3V, the internal charge

pump switch architecture dynamically selects an

operational mode that optimizes efficiency. The

SP6680 device regulates the maximum output

voltage in steady state to +6.3V.

THEORY OF OPERATION

There are seven major circuit blocks for the

SP6680 device. Refer to Figure 1.

1) The Voltage Reference contains a band gap

and other circuits that provide the proper current

biases and voltage references used in the other

blocks.

2) The Clock Manager accepts the digital input

voltage levels (including the input clock) and

translates them to V

if a clock is present in which case the device is

powered up. If the CLK input is left floating or

pulled near ground, the device shuts down and

V

is 0.4V and the worst case digital high is 1.3V.

This block contains a synthesizer that generates

the internal pump clock which runs at the

frequency controlled with the C/4 and Cx8 logic

pins.

3)

The Charge Pump Switch Configuration

Control determines the pump configuration

depending upon V

programs the Clock Phase Control. For an input

supply voltage from +2.7V to +3.7V, an X2

doubling architecture is enabled. This mode

requires one flying capacitor and one output

capacitor. For an input supply voltage greater

than +3.7V up to +6.3V, an X1.5 multiplier

architecture is enabled. This mode requires two

flying capacitors and one output capacitor.

Figure 1. Internal Block Diagram of the SP6680

Charge

Pump

Switches

Voltage

Reference

CF1P

CF1N

CLK

Cx8

C/4

Clock

Manager

Drivers

V

IN

GND

SP6680

2

9

8

6

5

4

3

Clock Phase

Control

Charge Pump Switch

Configuration Control

V

OUT

Control

V

OUT

1

CF2P

CF2N

10

7

CF2

C

OUT

CF1