TC1185-5 LDO VOLTAGE REGULATOR

[microic]

Hi to all,
Trying to design battery operated unit with ATTiny85 and 6V battery. Voltage regulator TC1185-5, I choose because I want to have 5V from battery, but when input is below 5V regulator just copy input to output. When Voltage on input is higher than 5 V output is regulated correctly. I use 1uF capacitors on both input and output. Already tried with two regulators, same result. I will appreciate any idea. Thanks, Damir

[moffy]

You could use something like a voltage monitoring circuit that at say 5.25V from the battery, bypasses the regulator with say a switched PMOS MOSFET in parallel with the regulator.

[ArdWar]

I'm not exactly sure what's the question here. TC1185 is a CMOS LDO, and just like most CMOS LDO with P-channel pass element it does revert to bypass mode once input voltage drops below regulation. No need for external bypass.

[xvr]

Voltage regulator TC1185-5, I choose because I want to have 5V from battery, but when input is below 5V regulator just copy input to output. When Voltage on input is higher than 5 V output is regulated correctly.

For LDO, like as any linear regulator, physically impossible to raise up input voltage - it can only dissipate some of them on itself (this is the way as linear regulators work) 

I will appreciate any idea.

Use switching mode regulator. You need some step up/step down regulator.
https://www.digikey.ie/en/products/filter/dc-dc-switching-controllers/715?s=N4IgjCBcpmAMVQGMoDMCGAbAzgUwDQgD2UA2iACxwAcAzAGwKFV0CcEzNtrtInbCALqEADgBcoIAMpiATgEsAdgHMQAX0IAmAKzbEIFJAw4CxMiFrVWcMKz4WrcWhRDCQ4yTIUr1hWGE19Q2M8QhJIcnowBiYQKIYOcHorCl4-ZNZWantozU0KehzaTVobIoB2Ck1swnL6azhY6PL4ROb4QL9aFqd7CnLqcs07LThNAb1R6ooXKepGe00x60Kp9jTwFu1WVc3aaMnN%2Bm0KEaPtek7z8tjyk%2B6a8%2BpEu%2B04GZzyyqpPyvoNsADVK7QGscaPMDUGyscqLarlUpwwa6JF1RJ5QYtezPMAUbSPDHldiLOAnN4ky75Cn5K5LeqpVyiCSQaRyJSqDTgVgUbLQAxoLChMwRCw7Y6M9zM1neDl%2BLJ2PnBQWmcLkIScvKwIICkxhcwQNweFkAESIAFcAEaYXC%2BEAAWgVyCgcjNKv1rk5dsCiudsldepFekEag15mNAGEAPQRiWFPnyAAmkjtrXsRpA9jEAE8RDaWehsCgQ0A

Or something ready made: https://www.digikey.ie/en/products/filter/dc-dc-converters/922?s=N4IgjCBcpgLA7BaIDGUBmBDANgZwKYA0IA9lANogBMVAHAKwAMsIAusQA4AuUIAylwBOASwB2AcxABfYmHpV6UUGkhY8RUhWqwAnGERtOPSPyFjJM8Dto6lqDDgLEykSozaWaYJMofrnWhDsINy8ACIkAK4ARtj40sQAtLbIKkKRGi6UQZaJVHZpghkBriCKrFKeWgAmKAD0tR5AA

[microic]

Hi to all,
thanks for answers,
I am in doubt because in data sheet for TC1165-5 is listed Vin Max 6V, Vin MIN 2.7V, output 5V.
I assume that output should be 5V in entire scale for Vin from 2.7 - 6V.

there are also other type of same LDO series  with different output Voltages , 1.8V,3.3V...
they also mention that is for battery operated circuits.
is there any one of you can suggest circuit from experience that is working for 5V output,cca 100mA. with connected 3V batteries in serie.
Thanks.

[xvr]

I am in doubt because in data sheet for TC1165-5 is listed Vin Max 6V, Vin MIN 2.7V, output 5V.
I assume that output should be 5V in entire scale for Vin from 2.7 - 6V.

No. See note 1 (for Vin parameter) after table:

The minimum VIN has to meet two conditions: VIN >= 2.7V and VIN >= VR + VDROPOUT.

is there any one of you can suggest circuit from experience that is working for 5V output,cca 100mA. with connected 3V batteries in serie.

Switching mode DC/DC only, not LDO.

[ArdWar]

I assume that output should be 5V in entire scale for Vin from 2.7 - 6V.

Nah, LDO can only shave excess voltage. They can't just add voltage out of nowhere.

You need some step up/step down regulator.

That's the "proper" solution, but for this low current it's often simpler to boost to 6V (or 5.5V if you got good LDO) and then regulate down to 5V with LDO. Boost converter is much more common and cheaper than buck-boost, and you get bonus lower noise here.