Hi,
I wanted to use Refleltor-D as power source for the reclocker Potato PO74G374A.
See DATASHEET.
So I set:
Vout as 3,25V DC (one green LED and JFET 2SK117GR (IDSS=3.8mA) in R6 position)
and R1=2.57ohm.
With a dummy resistor I can measure 3.25V DC on REF-D output. However when I connect Potato reclocker to Ref-D output voltage drop to 2.8 V DC. I've checked with other 3.3V Reflektor-D and is the same - change voltage from 3.3V to 2.8V...
Why is this happening?
Is this because the current consumption by the Potato PO74G374A is low?
How could I fix this to receive about 3.3V DC vout?
Thanks,
Bern
I wanted to use Refleltor-D as power source for the reclocker Potato PO74G374A.
See DATASHEET.
So I set:
Vout as 3,25V DC (one green LED and JFET 2SK117GR (IDSS=3.8mA) in R6 position)
and R1=2.57ohm.
With a dummy resistor I can measure 3.25V DC on REF-D output. However when I connect Potato reclocker to Ref-D output voltage drop to 2.8 V DC. I've checked with other 3.3V Reflektor-D and is the same - change voltage from 3.3V to 2.8V...
Why is this happening?
Is this because the current consumption by the Potato PO74G374A is low?
How could I fix this to receive about 3.3V DC vout?
Thanks,
Bern
Thanks Salas.
I will try two wire mode with my 3.3V ref-D soon and check if target voltage change significantly when I switch from testing/dummy resistor to target circuit with Potato PO74G374A.
Now I have other issue... I am going to use 4x5V DC Ref-D to supply DAC chips.
I need +5V and -5V separately for digital and analog part (so four Ref-D in total. Its crazy I know 😉).
I set one green and and orange LED and Jfet in R6 with about 3.5mA for all four Ref-Ds.
(This configuration gives me normally 5V Vout).
Dac chips needs:
+VCCD 8mA
-VCCD 80mA
+VCCA 60mA
-VCCA 40mA
So for +VCCD, +VCCA, -VCCA I use R1=3.1 ohm and for -VCCD R1=2.1ohm
Additionally for all four Ref-Ds I use RR=33ohm and J1 2SK117GR with IDSS=2.8-3.1mA.
Unfortunately I don't reach target Vout =5V. If I use R1=3.1 Vout in is actually about 4V and LEDs don't shine.
What should I change? R1 or J1 with higher IDSS and RR?
Or maybe should I investigate something before?
Thanks,
Maybe you use some heavy dummy load that hits the current limit and drops the voltage output? Because with 3.1R set resistor there is about 200mA available and with 2.1R about 290mA.
Yes. It's truth. I use 20ohm/5W.
What resistor value will be appropriate for testing Vout= 5V and current 10-60mA?
Thank you.
I have found 100R resistor and check three Ref-D having R1=3R1. It is OK. LEDs shine and I can measure 4.96-4.97 V DC Vout🙂
Astonishing...
When I switched from the four wire to two wire mode Vout is I expected e. g. about 3.3V DC and not 2.8V (I observed with four wire mode).
One thing puzzles me: relatively long distance (about 20cm) between Ref-D and 'power receiver'. How could I reduce adverse effect of the electromagnetic field in two wire mode...? Coaxial cable?
Regards,
im building this for amareno USB @ I2S. the specs say 0.602 Watt at full load at 5 volts VCC so i estimate 0.12 A at max. but i dont have a 1ohm resistor. is it ok to use a 1.5 ohm?
for R1
for R1
For 0.12A load even 1.5R seems way wasteful because it will allow 0.4A CCS. 3R for 0.2A seems better. Two 1.5R in series if not having a 3R handy.
this thing:
which leg is positive?
Has no polarity. Its a film capacitor. You solder it in any orientation you like.
When you don't know J1's IDSS use the smallest recommended RR value (47R) to be on the safe side. That way you know there will be enough current at least.
In the transistor kits, one 2SK117 should be marked with IDSS value, and is for this position.
The other is unmarked, and can be used in place of R6 as a mod (I believe). But this is mostly included for the Reflektor-Mini for use in J2 position.