SP6642EB/03

SP6642/3 Evaluation Board Manual

© Copyright 2000 Sipex Corporation

2

SP6642/3 EVALUATION BOARD

The next two sections describe the SP6642/3

Board Layout and Using the SP6642/3

Evaluation Boards. A table of SP6642/3 Pin

Assignments is also included with details

on Input/Output pin function. A SP6642/3

Evaluation Board List of Materials table is

provided with some manufacturers part numbers

to use as a reference. Finally, a schematic is

included of the SP6642/3 Evaluation Board.

BOARD LAYOUT

The SP6642/3 Evaluation Board has been

designed to easily and conveniently provide

access to all Inputs and Outputs of the SP6642/3

device under test. Position the board with the

silkscreen lettering upright (also see the drawing

on the front page of this manual) and you will

see the SP6642

µSOIC labeled U1 in the center

of the board, and above it the Capacitors C1,2,3

and Inductor L1 forming the DC-DC Converter

circuit.

The SP6642/3 Evaluation Board provides

convenient battery clips to connect the input to

an AAA Battery. Or, use the V

to directly connect to standard Power Supply

binding post outputs. 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

The SP6642/3 Evaluation Board can be

powered from a battery or a power supply.

Connect an AAA battery using the battery clips

labeled “+ “ and “-”. Or, directly connect the

SP6642/3EB board to a standard pair of power

supply binding posts (0.75" spacing) using the

“V

board with connections on the bottom). It is good

practice to not switch power on until power

connections are made to the evaluation board.

Powering Up the SP6642/3 Circuit

V

board directly to external Power Supply

binding post positive. V

Or, connect AAA Battery to clip labeled “+”.

GND – U1-6 – Connect GND post on bottom of

board directly to external Power Supply

binding post negative. Or, connect AAA Battery

to clip labeled “-”.

V

V

with R1 & R2 on FB pin. See Datasheet.)

GND – U1-6 – Second GND Connection to

Load, Meter or Scope GND.

Using the Shutdown Jumper J1

(SHDN only works with the SP6642)

The jumper J1 has 2 positions, as described

below. Shutdown is a feature on the SP6642, not

the SP6643. Connecting a logic low to SHDN

shuts off the internal switching MOSFET and

the synchronous rectifier opens to prevent

current from flowing back into the part. But, the

output can still drift to one diode drop below

V

input to output through the synchronous

rectifier body diode.

J1 — To start the SP6642, connect Shunt on J1

to the 1-2 position. The correct output voltage

(+3.3V) should appear on V

the SP6642, connect J1 to the 2-3 position.

Using the Power Fail Comparator, PFI

VTH — The SP6642EB is setup to trip the PFI

comparator when the input voltage is at the

PFI trip voltage (0.614V +/-3%). The threshold

voltage VTH (=V

R3 & R4, which sets a threshold voltage for PFI

comparator input pin 6 of U1. The user may set

a different trip voltage by selecting a resistor for

R4 (now open) using the equation:

R4 = R3*VPFI /(VTH -VPFI) whereVPFI = 0.614V

Note: To detect loss of power at the output, the

VTH threshold pin connection to V

severed leaving a connection to R3, which can

be used to connect to the output pin V