Datasheet

20050 SW 112
th
Ave. Tualatin, Oregon 97062 phone [phone] fax [phone]
rev.
page
date
rev.
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date
DESCRIPTION: point of load converter
11 of 12
08/2007
PART NUMBER: VPOL5A-12-SIP
7.8 VPOL5A-12-SIP Output Voltage Adustment.
The output Voltage of the VPOL5A-12-SIP can be adjusted in the range
0.75V to 5.0V by connecting a single resistor on the motherboard
(shown as R trim) in Figure 12. When Trim resistor is not connected the
output voltage defaults to 0.75V
+Vin
Common Common
+Vo
VPOL5A-12-SIP
R trim-up
R-Load
Trim
Figure 12. Trim-up Voltage Setup
The value of Rtrim-up defined as:
Where: Rtrim-up
is the external resistor in ohm,
Vo is the desired output voltage
To give an exa mple of the above calculation, to set a voltage of 3.3Vdc,
Rtrim is given by:
Rtrim = 3118 ohm
For various output values various resistors are calculated and provided
in Table 3 for co nvenience.
Vo,set (V) Rtrim (Kohm)
0.75 Open
1.2 22.33
1.5 13.00
1.8 9.00
2.0 7.40
2.5 5.00
3.3 3.12
5.0 1.47
Table 3 – Trim Resistor Values
7.9 Output Ripple and Noise Measurement
The test set-up for noise and ripple measurements is shown in Figure
13. a coaxial cable with a 50ohm termination was used to prevent
impedance mismatch reflections disturbing the noise readings at higher
frequencies.
Figure 13. Output Voltage Ripple and Noise Measurement Set-Up
7.10 Output Capacitance
CUI INC’s VPOL5A-12-SIP converters provide unconditional stability
with or without external capacitors. For good transient response low
ESR output capacitors should be located close to the point of load.
For high current applications point has already been made in layout
considerations for low resistance and low inductance tracks.
Output capacitors with its associated ESR values have an impact on
loop stability and bandwidth. CUI INC’s converters are designed to
work with load capacitance up-to 3,000uF. It is recommended that any
additional capacitance, Maximum 3,000uF and low ESR, be connected
close to the point of load and outs
ide the remote compensat
ion point.
0001 )
0.75
10500
(
Vo
Rtrim =
0001 )
3
10500
(Rtrim =
+Vin
Common Common
+Vo
R-Load
10uF
Tant.
1uF
Ceramic
Test Jack
VPOL5A-12-SIP
_
_
_
_
0.75
For more information, please visit the product page.