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ChulSung Lee
ChulSung Lee
Visitor II
August 8, 2017
Question

Question about Half-Bridge Output using L99MM70XP

  • August 8, 2017
  • 1 reply
  • 728 views
Posted on August 08, 2017 at 12:15

I am using L99MM70XP SBC.

I have one question about Half-Bridge Output.

Below Condtions, I think that All Half-Bridge output is Low (Open States)

0690X00000607xOQAQ.png

All High-Side / Low-Side Switch is Open. I think that PIN output Value is Low.(0 Volts)

But, Result is All Output is High (In Case Vbat Voltage is 13V , All Output Voltage is 13.5V)

Who can explain the above the result?

This topic has been closed for replies.

1 reply

Ignazio Testoni
Ignazio Testoni
ST Employee
August 31, 2017
Posted on August 31, 2017 at 14:08

Hello

chulsunglee

,

I understand that you have the CR1 in default configuration and you see that the output voltage in OPEN LOAD condition is the battery level.

In this case in fact all the half bridges are in tristate condition (OFF), means almost floating and even a very small leakage can bring the output to the battery voltage level.

Did you try to connect a small resistor (for example 10kOhm) to ground?

This resistor should be enough to discharge this leakage and bring effectively the output to ground.

In any case it is important to understand that:

BIT 0 means MOS OFF (whatever output is, HS or LS)

BIT 1 means MOS ON (whatever output is, HS or LS)

When an half bridge is in OFF condition does not means that its output voltage value is ZERO.

Instead means that the two power MOS are in tristate condition.

Best Regards.

Ignazio Testoni

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