
LSM-16A W3 Series
N O N - I S O L A T E D , W I D E I N P U T S M T D C / D C C O N V E R T E R S
6
"T" Model (LSM-T/16-W3)
This version of the the LSM-W3 series offers a special output voltage trim-
ming feature which is fully compatible with competitive units. The output
voltage may be varied using a single trim resistor from the Trim input (pin 5) to
Power Common (pin 3). The output voltage range is 0.75 Volts to 3.3 Volts.
IMPORTANT: For outputs greater than 3 Volts up to 3.3 Volts maximum, the
input supply must be 4.5 Volts minimum.
As with other trim adjustments, be sure to use a precision low-tempco resistor
(±100 ppm/°C) mounted close to the converter with short leads. Also be
aware that the output voltage accuracy is ±2% (typical) therefore you may
need to vary this resistance slightly to achieve your desired output setting.
The trim equation is as follows for the LSM-T/16-W3:
LSM-T/16-W3 xed resistance values to set the output voltages are:
Figure 7.Trim Connections Using Fixed Resistors
Figure 6.Trim Connections Using a Trimpot
Trim Equations
Note: Resistor values are in k
. Accuracy of adjustment is subject to
tolerances of resistors and factory-adjusted, initial output accuracy.
VO = desired output voltage. VO
NOM = nominal output voltage.
Note: Install either a xed
trim-up resistor or a xed
trim-down resistor depending
upon desired output voltage.
RTRIM (
) = _____________ –5110
VO – 0.7525
21070
VOUT (Typ.)
0.75V
1.0V
1.2V
1.5V
1.8V
2.5V
3.3V
RTRIM (k
)
Open
80.021
41.973
23.077
15.004
6.947
3.16
Voltage Trim
The LSM-T/16-W3 may also be trimmed using an external voltage applied
between the Trim input and Output Common. Be aware that the internal
“l(fā)oad” impedance looking into the Trim pin is approximately 5k
. Therefore,
you may have to compensate for this in the source resistance of your exter-
nal voltage reference.
The equation for this voltage adjustment is:
VTRIM (in Volts) = 0.7 –(0.1698 x (VO – 0.7525))
The LSM-T/16-W3 xed trim voltages to set the output voltage are:
VOUT (Typ.) 0.75V
1.0V
1.2V
1.5V
1.8V
2.5V
3.3V
VTRIM
Open
0.6928V 0.624V 0.5731V 0.5221V 0.4033V 0.267V
CAUTION: To retain proper regulation, do not exceed the 3.3V output