SP6642EB Datasheet, PDF (2/7 Pages) Sipex Corporation – Evaluation Board Manual

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 and GND posts
IN
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_IN” and “GND” posts (upper portion of the
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_IN – U1-1 – Connect V_IN post on bottom of
board directly to external Power Supply
binding post positive. V_IN = +0.85 to +1.65V.
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 – U1-8 – Connect to Load, Meter or Scope.
OUT
V = +3.3V. (Or, 2V to 5V if feedback is used
OUT
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 , since there is still a forward path from
BATTERY
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_OUT. To shutdown
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 ) connects to a voltage divider
IN
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) where VPFI = 0.614V
Note: To detect loss of power at the output, the
VTH threshold pin connection to V_IN can be
severed leaving a connection to R3, which can
be used to connect to the output pin V_IN.
SP6642EB/03
SP6642/3 Evaluation Board Manual
2
© Copyright 2000 Sipex Corporation