Datasheet

A single resistor connected from the Trim pin (pin 6) to the +Sense (pin 7)
will increase the output voltage. A resistor connected from the Trim Pin (pin 6)
to the –Sense (pin 5) will decrease the output voltage.
Trim adjustments greater than the specified range can have an adverse
affect on the converter’s performance and are not recommended. Excessive
voltage differences between VOUT and Sense, in conjunction with trim adjust-
ment of the output voltage, can cause the over-voltage protection circuitry to
activate (see Performance Specifications for over-voltage limits). Temperature/
power derating is based on maximum output current and voltage at the
converter’s output pins. Use of the trim and sense functions can cause output
voltages to increase, thereby increasing output power beyond the converter’s
specified rating, or cause output voltages to climb into the output over-voltage
region. Therefore:
(Vout at pins) x (Iout) ≥ rated output power
The Trim pin (pin 6) is a relatively high impedance node that can be suscep-
tible to noise pickup when connected to long conductors in noisy environments.
In such cases, a 0.22μF capacitor between trim and –Vout can be added to
reduce this long lead effect.
Where,
∆ = | (V
NOM − VOUT) / VNOM |
V
NOM is the nominal, untrimmed output voltage.
V
OUT is the desired new output voltage.
Do not exceed the specified trim range or maximum power ratings
when adjusting trim. Use 1% precision resistors mounted close
to the converter on short leads.
Trim Equations
(For all models except the UCQ-1.2/40-D24 and -1.2/30-D48)
Trim Down
Connect trim resistor between
trim pin and −Sense
∆
5.11
R
TrimDn
(k Ω) =
− 10.22
Trim Up
Connect trim resistor between
trim pin and +Sense
1.225 × ∆
5.11 × VNOM × (1+∆)
R
TrimUp
(k Ω) =
− 10.22
∆
− 5.11
Trim Equations
(For the UCQ-1.2/40-D24 and -1.2/30-D48)
Trim Down
Connect trim resistor between
trim pin and −Sense
2∆ − 2
5.11
R
TrimDn
(k Ω) =
Trim Up
Connect trim resistor between
trim pin and +Sense
1.225 × ∆
5.11 × VNOM × (1+∆)
R
TrimUp
(k Ω) =
LOAD
R
TRIM DOWN
+VOUT
+VIN
–VIN
ON/OFF
CONTROL
TRIM
+SENSE
–VOUT
–SENSE
4
5
1
3
6
8
7
2
Figure 7. Trim Connections To Decrease Output Voltages Using Fixed Resistors
LOAD
R
TRIM UP
+VOUT
+VIN
–VIN
ON/OFF
CONTROL
TRIM
+SENSE
–VOUT
–SENSE
4
5
1
3
6
8
7
2
Figure 6. Trim Connections To Increase Output Voltages Using Fixed Resistors
LOAD
5-22
TURNS
+VOUT
+VIN
–VIN
ON/OFF
CONTROL
TRIM
+SENSE
–VOUT
–SENSE
4
5
1
3
6
8
7
2
Figure 5. Trim Connections Using A Trimpot
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Single Output UCQ Models
Low-Profile, Quarter Brick, 8.3-40 Amp
Isolated DC-DC Converters
MDC_UCQ Models.E02 Page 23 of 24