Rev. 6/27/01

SP66680 Evaluation Board Manual

© Copyright 2001 Sipex Corporation

2

The SP6680 Evaluation Board provides convenient test points to connect the input to

Power Supply or Li-Ion Battery. The Input and Output connections are made with

raised female pin receptacles which can accommodate easy-hook connection leads for

power and meter connections, as well as scope probe hooks and grounds for waveform

measurements.

USING THE EVALUATION BOARD

1) Powering Up the SP6680 Circuit

The SP6680 Evaluation Board can be powered from a single Li-Ion battery or a +2.7 to

+6.3V power supply. Connect with short leads directly to the “Vin” and “Gnd” posts.

Note the SP6680 will remain in “shutdown” until a Clock input is applied to the “CLK”

input post.

2) Enabling the SP6680 Output with CLK Input

The SP6680 output will typically be in low current “shutdown” mode until a Clock Input is

applied to the “CLK” post. This input typically is a CMOS level 32.768kHz clock derived

from a real-time clock crystal, but any stable square wave function generator with a

of 5.2V to 6.3V with a voltmeter or scope across the “Vout” and “Gnd” posts.

3) Controlling the Pump Frequency

The SP6680 has 3 frequency modes controlled by the presence of a 32.768kHz Clock

at “CLK” input, and levels at the digital inputs at posts “CD4” or “CX8”. Basically, the

SP6680 will pump at the 32.768kHz Clock input frequency unless a High level is

present at CD4 or CX8, as illustrated in the Pump Frequency Control table below.

Apply Logic High to “CD4” post and the SP6680 will pump at ¼ frequency or 8.192kHz.

Or, apply a Logic High to “CX8” post and the SP6680 will pump at 8 times the Clock

frequency or 262.14kHz. Observe the pump frequency by applying a scope probe to

CF2P post.

TABLE1: PUMP FREQUENCY CONTROL

As you can see from the table, as pump frequency increases, the capability of the

SP6680 maximum output current increases (and quiescent current will rise). See the

SP6680 datasheet specification table to compare how the Output Resistance, Output

Voltage and Power Efficiency parameters vary with Pump Frequency.

4) Dynamic Charge Pump Action

The charge pump configuration dynamically changes to optimize efficiency. At low input

voltages the charge pump doubles the input, while at higher inputs the output is 1.5

times the input. You can observe this action by monitoring how the output voltage

CLK pin

CD4

CX8

Fpump Frequency

Maximum Output

not present

X

X

0

0

32.768kHz

Low

Low

32.768kHz

20mA

32.768kHz

Low

High

262.14kHz

60mA

32.768kHz

High

Low

8.192kHz

2mA

32.768kHz

High

High

262.14kHz

60mA