Datel 20A manual Trim Equations, USQ-1.2/20-D48

USQ Series 2 0 A , S I N G L E O U T P U T D C / D C C O N V E R T E R S

Standard USQ's have a "positive trim" where 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. DATEL also offers a "negative trim" function (D suffix added to the part number). Contact DATEL for information on negative trim devices.

Trim adjustments greater than the specified +10%/–20% 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 adjustment of the output voltage, can cause the overvoltage protection circuitry to activate (see Performance Specifications for overvoltage limits).

Temperature/power derating is based on maximum output current and volt- age 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 USQ's specified rating, or cause output voltages to climb into the output overvoltage 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 environ- ments. In such cases, a 0.22µF capacitor can be added to reduce this long lead effect.

1	–INPUT	+OUTPUT	8
		+SENSE	7
2	ON/OFF	TRIM	6
	CONTROL		LOAD
			RTRIM UP
		–SENSE	5
3	+INPUT		4
		–OUTPUT

Figure 5. Trim Connections To Increase Output Voltages Using Fixed Resistors

1	–INPUT	+OUTPUT	8
		+SENSE	7
2	ON/OFF	TRIM	6
	CONTROL		LOAD
			RTRIM DOWN
		–SENSE	5
3	+INPUT		4
		–OUTPUT

Trim Equations

USQ-1.2/20-D48

RT UP (kΩ) =			1.308(VO – 0.793)		–1.413	RTDOWN (kΩ) =			1.037	–1.413
									1.2 – VO
				VO – 1.2
					USQ-1.5/20-D48
RT UP (kΩ) =				6.23(VO – 1.226)	–10.2	RTDOWN (kΩ) =			7.64	–10.2
				VO – 1.5					1.5 – VO
					USQ-1.8/20-D48
RT UP (k	Ω	) =		7.44(VO – 1.226)	–10.2	RTDOWN (k	Ω	) =	9.12	–10.2
				VO – 1.8					1.8 – VO
					USQ-2.5/20-D48
RT UP (kΩ) =				10(VO – 1.226)	–10.2	RTDOWN (kΩ) =			12.26	–10.2
				VO – 2.5					2.5 – VO
					USQ-3.3/20-D48
RT UP (kΩ) =				13.3(VO – 1.226)	–10.2	RTDOWN (kΩ) =			16.31	–10.2
				VO – 3.3					3.3 – VO
				USQ-5/20-D24, -D48
RT UP (kΩ) =				20.4(VO – 1.226)	–10.2	RTDOWN (kΩ) =			25.01	–10.2
				VO – 5					5 – VO
				USQ-12/8.3-D24, -D48
RT UP (kΩ) =				49.6(VO – 1.226)	–10.2	RTDOWN (kΩ) =			60.45	–10.2
				VO – 12					12 – VO
				USQ-15/6.7-D24, -D48
RT UP (kΩ) =				62.9(VO – 1.226)	–10.2	RTDOWN (kΩ) =			76.56	–10.2
				VO – 15					15 – VO
				USQ-18/5.6-D24, -D48
RT UP (kΩ) =				75.5(VO – 1.226)	–10.2	RTDOWN (kΩ) =			92.9	–10.2
				VO – 18					18 – VO
				USQ-24/4.2-D24, -D48
RT UP (kΩ) =				101(VO – 1.226)	–10.2	RTDOWN (kΩ) =			124.2	–10.2
				VO – 24					24 – VO

Note: Resistor values are in kΩ. Adjustment accuracy is subject to resistor tolerances and factory-adjusted output accuracy. VO = desired output voltage.

Figure 6. Trim Connections To Decrease Output Voltages Using Fixed Resistors

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