# Switching Power supply output specified 5.1 VDC is important ?

#### ch.imran

Joined Oct 26, 2022
5
A PCB using bord mounted switching power supply 230VAV to 5.1 VSC. does another power supply with output voltage 5.0 VDC will work for that circuit bord to function properly? how much difference 0.1 VDC will make in proper functioning of the equipment?

#### Dodgydave

Joined Jun 22, 2012
11,241
There won't be any issues for 100mV drop.

#### DickCappels

Joined Aug 21, 2008
10,123
Back in the days when TTL was king or digital, the low voltage power supplies were specified at 5% (5V±0.25V) later CMOS devices can work over a wider range, so there is little to worry about unless you have some poorly designed analog circuitry.

#### dl324

Joined Mar 30, 2015
16,688
Welcome to AAC!
how much difference 0.1 VDC will make in proper functioning of the equipment?
As usual, it depends.

A difference of 0.1V is 2%. Any well-designed product will have a voltage tolerance higher than that. The problem for you is that you could have something that's poorly designed...

#### ch.imran

Joined Oct 26, 2022
5
the circuit is not expected to be poorly designed, because it belongs to an industrial grade equipment. unfortunately, I am unable to purchase this component from same manufacturer. i have mentioned specs of the PS used. i have never seen any PS unit designed to produce 5.1 VDC, commonly 5.0 or 12.0 volts are used, my concern is what could be the reason to use this output voltage and how much possibility is there if OEM customised the PS unit to ensure customer has to reach back to them only for maintenance.

considering everything, is it safe if I replace this PS unit with any available unit with Output 5.0 VDC?

INPUT: 100-240 V AC 180-90 mA 60/50 HZ
OUTPUT: 5.1 V DC, 1600 mA

Output Voltage Accuracy: ±3,0%
Ripple: I load=I nom BW=1MHz ≤1%
Noise ( ≤30MHz ): I load=I nom.; BW=30MHz: ≤2%
Temperature Coefficient: -40°C ≤ Ta ≤ +85° 0,02%/K max.
Response Time ( 70 – 100% ): (10% - 90%)*Inom ≤2,5ms
Short Circuit Protection : Continuous
Short Circuit Current: ≤1,5*Inom
Line Regulation: I load = I nom ≤0,1%
Isolation Voltage I/O. 3,75K VAC
Switching Frequency 67 KHz
Operating Temperature Range -40°C to +85°C
Derating above 55°C: 5,1V 1,76%/K
Derating above 50°C Output 5V / 2A 2,5%/K
Over Temperature Protection: Measured Middle of Case: 100°C
Electrical Safety (Approved): Output 5.1V

#### Ian0

Joined Aug 7, 2020
9,503
Your output voltage is 5.1V±3%. That’s from 4.947V to 5.253V.
What limits or error are specified on your 5V supply?

#### MrChips

Joined Oct 2, 2009
30,488
0.1 in 5 is ±2%
The PSU spec is ±3%
It will be fine.

#### Ian0

Joined Aug 7, 2020
9,503
There were no limits of error specified on the 5.0V supply in post #1.

Don‘t forget that one is equal to two for large values of one and small values of two.

#### dl324

Joined Mar 30, 2015
16,688
considering everything, is it safe if I replace this PS unit with any available unit with Output 5.0 VDC?
Just make sure it conforms to all of the other relevant specs of the supply you intend to replace.

#### DickCappels

Joined Aug 21, 2008
10,123
At that kind of current (1.6A and below) the 0.1V will probably be dropped by the interconnecting cable anyway. Don't worry.

#### ch.imran

Joined Oct 26, 2022
5
There were no limits of error specified on the 5.0V supply in post #1.

Don‘t forget that one is equal to two for large values of one and small values of two.
i may find another PS unit with output 5.0 VDC with 2% accuracy.

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#### ch.imran

Joined Oct 26, 2022
5
Just make sure it conforms to all of the other relevant specs of the supply you intend to replace.
Thanks for your support, surely i will try my best. but again, to find specs if 1.6 A, Noise and ripple seems difficult. i found PSU 1.0 A, 2A, 2.4 A.

#### MrChips

Joined Oct 2, 2009
30,488
I think you are splitting hairs here.
5.1V output from a PSU rated at 5.0V is very common.
That is because they anticipate losing about 0.1V on cabling at full power output.

#### dl324

Joined Mar 30, 2015
16,688
Thanks for your support, surely i will try my best. but again, to find specs if 1.6 A, Noise and ripple seems difficult. i found PSU 1.0 A, 2A, 2.4 A.
Higher current is probably okay; assuming the device being powered provides self-protection.

Since you don't seem inclined to tell us anything about the device that's being powered, it's up to you to determine which specs are relevant. Since the device uses an external power supply, certification for being operated from line voltage comes from the power supply approvals.

Joined Jul 18, 2013
28,513
i may find another PS unit with output 5.0 VDC with 2% accuracy.
At one time, in the age of linear regulated supplies, it was not uncommon to see a pair of destination source terminals on the P.S.
This entailed running a small pair of conductors to the load, to sense any volt drop that may occur, particularly with long load conductor runs, the regulator would then attempt to maintain the voltage at destination, by raising the source accordingly.