SP6642EB Datasheet, PDF (3/7 Pages) Sipex Corporation – Evaluation Board Manual

PFO – U1-3 – SP6642 or U1-4 – SP6643 Open
Drain Power Fail Output. Sinks current when
PFI falls below 0.614V. The SP6642EB has
this pin pulled up to V_OUT through 100kΩ
resistor R5, which will draw 30µA when
power fail is asserted low.
Evaluating Output Voltages Other than 3.3V
FB – U1-5 – Connects to R1, R2 output
feedback divider. The SP6642/3EB is set for
3.3V output since R1 is open on the board, and
R2 shorts FB to GND. To set an output voltage
in the range 2V to 5V, first cut the short on the
board across R2, then connect surface mount
resistors R1 & R2 according to the voltage
divider equation:
R1 = R2 (V /VREF - 1)
OUT
where R2 should be 100K to 1M since FB
leakage = 10nA max and VREF = 1.25V
Evaluating the SP6643 Circuit
The SP6642EB comes with a SP6642EU
installed. To evaluate a SP6643, you need to
order samples of the SP6643EU and install one
on the board. Instead of having the SHDN
function, the SP6643 has a BATTLO function,
which gives a low battery detection when the
battery voltage drops below 1V. Be sure to
remove the Shunt in J1 when using the SP6643.
There are two pins on the SP6643 that differ
from the SP6642, so note their use and label
names differ as shown below:
BATTLO – U1-3 Use the post labeled PFO. The
BATTLO on the SP6643 is an Open Drain
Battery-Low Output which is pulled up to V_OUT
by 100kΩ resistor R5. When the voltage at
the BATT pin is less than 1V, BATTLO goes to
close to 0V indicating Low Battery.
PFO – U1-4 Use the post labeled SHDN.
Remove the Shunt from J1. The PFO function
on the SP6643 behaves the same as the SP6642
as described previously in the section “Using
the Power Fail Comparator PFI”.
SP6642EB/03
SP6642/3 Evaluation Board Manual
3
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