ZY2120 Power-One, ZY2120 Datasheet - Page 14

• Manufacturer Part Number: ZY2120
• Description: Zy2120 20a No-bus Pol
• Manufacturer: Power-One

9.
9.1
Resistance of the trim resistor is determined from the
equation below:
where V
If the R
PGND, the V
9.2
Margining can be implemented by changing the
resistance between the REF and TRIM pins.
In the schematic shown in Figure 12, the nominal
output voltage is set with the trim resistor R
calculated from the equation in the paragraph 9.1.
Resistors R
output voltage up and down respectively and
determined from the equations below.
ZD-02139 Rev. 1.0 04NOV08
Up Switch
Margining
R
(normally
TRIM
open)
Application Information
R
R
Output Voltage Programming
Output Voltage Margining
UP
=
DOWN
OUT
TRIM
20
=
Figure 12. Margining Configuration
×
is the desired output voltage in Volts.
UP
20
20
is open or the TRIM pin is shorted to
OUT
5 (
R
=
V
and R
×
+
UP
5 .
Down Switch
OUT
(
=0.5V.
20
R
R
Margining
(normally
−
closed)
TRIM
TRIM
V
+
OUT
R
DOWN
TRIM
×
)
⎛
⎜ ⎜
⎝
,
5
R
)
kΩ
are added to margin the
×
×
R
DOWN
R
⎛
⎜
⎝
TRIM
100
TRIM
Δ
V
Δ
−
%
V
−
Δ
%
Δ
MARGIN
TRIM
GND
V
V
%
%
⎞
⎟
⎠
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⎞
⎟ ⎟
⎠
, kΩ
, kΩ
POL
TRIM
8V to 14V Input
ZY2120 20A No-Bus POL Data Sheet
where R
ΔV% is the absolute value of desired margining
expressed in percents of the nominal output voltage.
During normal operation the resistors are removed
from the circuit by the switches.
Down” switch is normally closed shorting the resistor
R
open disconnecting the resistor R
An alternative configuration of the margining circuit is
shown in Figure 13.
switches
advantageous in some implementations.
R
from the following equations:
Caution:
Refer to No-Bus
Note on
information on this and other product features.
Up Switch
Margining
(normally
DOWN
UP
open)
and R
R
Figure 13. Alternative Margining Configuration
R
UP
while the “Margining Up” switch is normally
DOWN
TRIM
Noise injected into the TRIM node may affect accuracy
of the output voltage and stability of the POL
converter. Always minimize the PCB trace length from
the TRIM pin to external components to avoid noise
pickup.
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=
DOWN
are
Down Switch
20
20
is the value of the trim resistor in kΩ and
R
Margining
(normally
=
×
+
UP
open)
for this configuration are determined
20
20
R
R
normally
TM
TRIM
TRIM
Preliminary Data Sheet
×
+
R
R
POL Converters.
•
TRIM
TRIM
×
0.5V to 5.5V Output
⎛
⎜ ⎜
⎝
In the configuration both
5
×
R
R
×
open
⎛
⎜
⎝
TRIM
DOWN
R
100
TRIM
Δ
for more application
V
Δ
Page 14 of 15
UP
−
V
%
.
−
Δ
%
that
The “Margining
Δ
V
MARGIN
TRIM
GND
V
%
%
⎞
⎟
⎠
Application
, kΩ
⎞
⎟ ⎟
⎠
may
, kΩ
POL
be