TPS61390EVM-020: Test process problems

Jianing Zhu

Part Number: TPS61390EVM-020
Other Parts Discussed in Thread: TPS61390

Hi,

We want to use TPS61390 in PON for APD power supply. For the EVM test process, we meet following problems:

1. How to choose MON1 & MON2. Could it be chosen automatically? Or we need to use GAIN pin?

2.For APF dynamic load test, does it mean we need to add an external 1.15V to gate? We link the 1.1V on the EVM to gate, it didn't work

3.How to realize the Sample and Hold function?

Thanks,

over 3 years ago

+1 Yichen Xu over 3 years ago

TI__Expert 4760 points

Hi Jianing,

1.This AN described MON in detail:https://www.ti.com/lit/an/slvaeh5/slvaeh5.pdf?ts=1645606313976&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FTPS61390.

2.Yes, 1.1Vmay not reach threshold of the MOS, it could be 1mA when using 1.15V.

3.For sample and hold, VSP is Sample/Hold voltage output with single-ended output. An external ADC can sense the voltage of the output of the operational amplifier to measure the optical intensity. The sample and hold is enabled by the rising edge of an external clock connecting to the SAMPLE pin, the holdup capacitor captures the voltage of current mirror signal (the voltage of MON1 and MON2).The minimum time of the sampling time the TPS61390 supports is 350 ns (typically).

0 Jianing Zhu over 3 years ago in reply to Yichen Xu

TI__Expert 4325 points

Hi Yichen,

Thanks for your reply.

Actually the MOS need 1.7V-2.0V on gate to open. After it is opened, it seems to work abnormally.

After the MOS open, the voltage on R15 is 0.397V, thus the current should be 0.397V/100Ω=0.00397A=3.97mA. But actually Vmon2=1.11V, Vmon1=1.6V, Vgain=3.3V, VSP=2.25V.

The abnormal point is: VSP≠4*MON2, VSP(2.25V)≠4*0.2*Iapd*RMON2+4*Ibias*RMON2（0.8*0.00397*3k+4*20*10-6*3k=9.768V）

What is the possible cause? Thanks.

+1 Yichen Xu over 3 years ago in reply to Jianing Zhu

TI__Expert 4760 points

Hi Jianing,

Eric will reply in the email, so I will close this thread.

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TPS61390EVM-020: Test process problems