TDK iFA Series manual Figure Trim Down Connection

Advance Data Sheet: MaxetaTM iFA Series

If the output voltage adjustment feature is not used, the Vout(+) pin should be shorted to the sense(+) pin and the Vout(-) pin should be shorted to the sense(-) pin by jumper wires.

S(+)
Vo(+)
Co	Load
Vo(-)
S(-)
Trim
Rext2

Figure Trim Down Connection

To trim the output voltage down, a fixed or variable resistor, Rext2, shall be connected between the trim pin and the sense(-) pin while the Vout(-) pin and the sense(-) pin are shorted by a jumper wire. Vout(+) pin and the sense(+) pin should also be shorted by a jumper wire as shown below. The resistor, Rext2, can be chosen according to the following equation:

In order to trim the output voltage from the minimum value (-40% down) to the maximum value (+10% up) in a linear fashion, a fixed resistor, Rext, should be connected between the trim pin and the sense(-) pin while a 50KΩ variable resistor, Rv, shall be connected between the Vout(+) pin and the sense(+) pin as shown below. When Rext=5.11KΩ, the voltage trim rate is changed to approximately 0.459V / KΩ starting from 16.8V. The resistor, Rv, should be chosen according to the following equation:

Rv ≅ 2.17833 × (Vo_d – 12.862) (KΩ)

where Vo_d is the desired output voltage.

	Rv
S(+)
Vo(+)
	Co	Load
Vo(-)
S(-)
Trim
	Rext
Figure	Linear Trim Connection

Rext2

Vo_down + 0.331

4.787591 − 0.171506Vo_down

Trim-down Resistance vs. Vout

10000
	1000
(KU)
Resistance	100
	10
Trim
	1
	16	18	20	22	24	26	28
			Output Voltage (V)

Linear Trim Resistance vs. Vout

	40.0
	36.0
)	32.0
(K
Resistance	28.0
	24.0
	20.0
Trim	16.0
	12.0
	8.0
	16	19	22	25	28	31

Output Voltage (V)

©2005 TDK Innoveta Inc.		￿ (877) 498-0099
iFA Advance Datasheet	6/6/2005	14/18