TPS63700: TPS63700

Hamza MAKHLOUK

Part Number: TPS63700

Hello,

i am using the TPS63700 DC-DC inverter to generate -15V output voltage (0.15A) from a 6V as in the schematic bellow (fig 1), the Diode dropout the input Voltage to do not exceed the maximum input Voltage,

I am getting -16.4V instead of -15V, i have tried feedback resistor combinaison by setting R308 + R305 to 161KOhm and R306 to 2Mega Ohm and still not got the required output voltage (resistor tolerance is +-0.1%).

i've checked the Vref which seems to be ok (1.213V) the Schottky Diode breakdown voltage is 30V, i've also changed the C310 to 4.7nF as recemanded and anlso isolated the circuit and applied directly a 5V input Voltage but i still not got -15V output voltage.

fig1:

I have also tried the configuration bellow but still got no -15V

Do you have any suggestions ??

Hope to hear from you soon.

Best regards.

over 2 years ago

0 Bryce Xun over 2 years ago

TI__Mastermind 27880 points

Hi Hamza,

What is the purpose of the circuit I marked below, can you try with R84 and R5 removed?

BRs,

Bryce

0 Hamza MAKHLOUK over 2 years ago

Prodigy 20 points

Hello Bryce yes currently i've removed them (R5,R84). i'm using the schematic in fig1.

the resistor values are the following R308=1KOhm, R305=161KOhm and R306=2MegOhm. all resistor are +-0.1% tolérance. Vout = -Vref*R306/(R305+R308)= -15.06(based on the datasheet) but i still don't get the required Voltage.

best regards.

Hamza

0 Bryce Xun over 2 years ago in reply to Hamza MAKHLOUK

TI__Mastermind 27880 points

Hi Hamze,

1. What is the load current during the test?

2. Can you probe the waveforms of Vin, Vout, SW and iL at one page?

3. Also can you share with your layout here?

BRs,

Bryce

0 Hamza MAKHLOUK over 2 years ago in reply to Bryce Xun

Prodigy 20 points

Hello Bryce,

I've resolved the problem§ now i'm getting -15V accros different load as attached!

Thank you for your valibale proposition.

With best regard.

Hamza.

+1 Bryce Xun over 2 years ago in reply to Hamza MAKHLOUK

TI__Mastermind 27880 points

Hi Hamza,

Glad to know that, you are welcome, can you also share your debug experience here? Thanks.

BRs,

Bryce

0 Hamza MAKHLOUK over 2 years ago in reply to Bryce Xun

Prodigy 20 points

Hi Bryce!

Actually i was not driving the dc-dc with enough load! i'm driving it now to get 0.1A and it's working!!! But with no Load i'm getting -16.38V. and the lowest current load i have to acheive to get the -15V is 0.012A (so i've changed my schematics by placing 1Kohm resistor in the output to meet my requirments). so maybe the dc-dc invertors requires a minimum load (it was the first time getting this porblem).

0 Bryce Xun over 2 years ago in reply to Hamza MAKHLOUK

TI__Mastermind 27880 points

Hi Hamza,

Thanks for feedback, based on the description, in further light load, the device would get into skipping mode, if you could share some waveforms of Vin, Vout, SW, iL, it will be better for understanding.

BRs,

Bryce

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TPS63700: TPS63700