TLV1117: TLV1117c output problem

Hi,

The voltage measured across R1 could be different from Vref for a variety of reasons. There could be another component downstream from the regulator that is holding the output. The input voltage could also be too low causing the regulator to operate in dropout. With this in mind could you please provide some additional information:

1. Input voltage
2. Load current
3. Voltage measured across R1
4. Are there any additional components connected to the TLV1117 output in your circuit that are not shown in Figure 9 of the datasheet?

A schematic would also be very helpful towards understanding your issue.

Thanks,
Gerard

Thanks for your reply.

Please find additional information below for your reference:

1, Vi = 8v

2, I didn´t measure load current. but Iadj = 80µA. 

4, No additional componenets are connected but, i have not connected Cadj in the circuit. The rest cuircuit is exactly same.

Thanks

Drashti

Hi Drashti,

You have enough headroom (Vin - Vout = 3 V) to ensure that the regulator should not be operating in dropout.

I apologize for not asking this previously, but what output voltage are you measuring? If it is higher than expected, keep in mind that the TLV1117 has a 5 - 10 mA bias current that must be consumed by the load and/or feedback network to ensure proper regulation. As your resistor network will only consume 0.38 mA with a 5 V output, the load current will need to be about 10 mA or larger. 

Thanks,

Gerard 

Hi Mr. Gerard,

I am measuring 3,3v and 5v output. 

Thanks 

Drashti

Hi Drashti,

I understand that you are choosing R1 and R2 to configure the TLV1117 for 3.3 V and 5 V, but you mentioned you are not getting the desired output. What output voltages are you measuring instead?

Please also confirm that your load current is 10 mA or larger. You can ensure this by adding a load resistor between 10 ohms and 330 ohms connected between the TLV1117 output and ground.

Thanks,
Gerard