EEVblog Electronics Community Forum
Electronics => Repair => Topic started by: hns0 on April 13, 2023, 06:15:23 pm
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I'm trying to repair an old 1990s camera with a dead 5V boost converter circuit.
The switching controller chip, IC201 in the schematic, is a Ricoh RS5RM5045B, which isn't available any more. I'm hoping for either a drop-in replacement or to make a small bodge board to patch in a new 5V regulator circuit.
The Ricoh chip has a couple differences from other boost converters I've seen. There's an active-low CE pin to turn on the 5V boost on Vout, and when it is high (disabled), it passes through the 3V battery Vin directly to Vout. So the main CPU is powered by 3V Vin in standby, and boosted 5V when switched on.
Does anyone know of a regulator IC with this functionality? Any advice would be much appreciated!!
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RS5RM5045A is still available and should work just fine.
https://www.utsource.net/sch/RS5RM5045A.html (https://www.utsource.net/sch/RS5RM5045A.html)
https://www.aliexpress.com/item/1005003634032023.html (https://www.aliexpress.com/item/1005003634032023.html)
Designation of Version Symbols:
A: Operation of all the internal circuits is stopped by setting CE pin at VDDlevel.
B: Operation of only Step-up DC/DC converter is stopped by setting CE pin at VDDlevel.
EDIT: seems you will need to bodge a schottky diode from Vbat to VOUT so VOUT still will have voltage when CE input is disabled.
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Great idea to use the A version with a schottky diode. I will give this a try. thanks!