PI33XX Datasheet, PDF (35/42 Pages) Vicor Corporation – 8V to 36Vin Cool-Power ZVS B uck Regulator Family

For more information about how to utilize the I²C
interface please refer to Picor application note
PI33XX-2X I²C Digital Interface Guide.
Application Description
Output Voltage Trim
The PI33XX family of Buck Regulators provides seven
common output voltages: 1.0V, 1.8V, 2.5V, 3.3V,
5.0V, 12V and 15V. A post-package trim step is
implemented to offset any resistor divider network
errors ensuring maximum output accuracy. With a
single resistor connected from the ADJ pin to SGND
or REM, each device’s output can be varied above or
below the nominal set voltage (with the exception of
the PI3311-X0 which can only be above the set
voltage of 1V).
Device
PI3311-X0-LGIZ
PI3318-X0-LGIZ
PI3312-X0-LGIZ
PI3301-X0-LGIZ
PI3302-X0-LGIZ
PI3303-X0-LGIZ
PI3305-X0-LGIZ
Output Voltage
Set
Range
1.0V 1.0 to 1.4V
1.8V 1.4 to 2.0V
2.5V 2.0 to 3.1V
3.3V 2.3 to 4.1V
5.0V 3.3 to 6.5V
12V 6.5 to 13.0V
15V 10.0 to 16.0V
Table 3 - PI33XX family output voltage ranges
The remote pin (REM) should always be connected
to the VOUT pin, if not used, to prevent an output
voltage offset. Figure 4 shows the internal feedback
voltage divider network.
R4
R1
-
+
R2
1.0Vdc
VOUT
REM
ADJ
R_low
SGND
R_high
Figure 4 - Internal resistor divider network
vicorpower.com
800 735.6200
PI33XX-X0
R1, R2, and R4 are all internal 1.0 % resistors and
R_low and R_high are external resistors for which
the designer can add to modify VOUT to a desired
output. The internal resistor value for each
regulator is listed below in Table 4.
Device
R1
R2
R4
PI3311-X0-LGIZ 1k Open 100
PI3318-X0-LGIZ 0.806K 1.0k 100
PI3312-X0-LGIZ 1.5k 1.0k 100
PI3301-X0-LGIZ 2.61k 1.13k 100
PI3302-X0-LGIZ 4.53k 1.13k 100
PI3303-X0-LGIZ 11.0k 1.0k 100
PI3305-X0-LGIZ 14.0k 1.0k 100
Table 4 - PI33XX Internal divider values
By choosing an output voltage value within the
ranges stated in Table 3, VOUT can simply be
adjusted up or down by selecting the proper R_high
or R_low value, respectively. The following
equations can be used to calculate R_high and R_low
values:
(
)()
()
()
(
)()
If, for example, a 4.0V output is needed, the user
should choose the regulator with a trim range
covering 4.0V from Table 3. For this example, the
PI3301 is selected (3.3V set voltage). First step
would be to use Equation (1) to calculate R_high
since the required output voltage is higher than the
regulator set voltage. The resistor-divider network
values for the PI3301 are can be found in Table 4 and
are R1=2.61kΩ and R2=1.13kΩ. Inserting these
values in to Equation (1), R_high is calculated as
follows:
(
)(
)
Rev 1.4
11/2012
Cool-Power^®
Page 35 of 42