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# TPS57060-Q1: Divider for Wide range Enable signal

Part Number: TPS57060-Q1

Hi Champs,

My customer would like to apply TPS57060-Q1 for Primary DCDC.

There are two input rails, Battery and IG, both rails have range from 10V to 32V as operating range, and 50V max.

IG rail is used to enable TPS57060-Q1, but the device doesn't have enough range as VIN port, divider circuitry would be required.

I attach the calculation as attached, could you check and suggest better solution?

Condition:

- IG input range : 10V to 32V as operation voltage, 50V for tolerance

- Assume if VEN >= 5.8V, internal zener sink 100uA through 10kohm built in resistance as shown in Figure 27.

- If VEN < 5.8V, VEN is defined by IG ,R1, and R2.

- VEN is set as 1.5V (with margin) when IG is 10V

Best regards,

TPS57060EN.xlsx

• Hello Nobuo,

The problem that you face cannot be solved by adjusting the divider components. This is because you desire a 10:1 ratio of maximum input voltage and minimum input voltage while the EN pin is only designed to handle a 4:1 ratio. There are two solutions:

1) Include a protection Zener in your EN divider.
2) Leave the EN pin open which will result in the part operating using only its internal UVLO rather than using the EN pin as a UVLO.

Regards, Robert
• Hi Robert,

For the answer 1), could you check my previous attached excel sheet?

The calculation is based on the idea to use built-in zener which has 5.8V Break-down voltage and 100uA sink ability via built-in 10kohm resister, and description written in p15 of datasheet, just above Figure 29.

Regarding to answer 2), leaving EN pin open does not satisfy customers system use case, because system requires IG to control enable of DCDC.

So could you check TPS57060EN.xlsx attached in my previous question?

Thanks and best regards,

• Hello Nobuo,

I have checked your spreadsheet and found that it can be used to check the maximum IG voltage but does not take into account:

1) The 10k in series with the Zener

2) The Zener’s ability to sink currents between 0 uA and 100 uA.

Since the datasheet does not give specifics concerning the Zener, I found that a simpler approach is to simply calculate the maximum voltage allowed on IG.  See attached file.  Note that the ABS MAX value and the value calculated this way conflict, which may be the result of variation in the Zener’s blocking voltage.

In any case, both methods indicate that your divider is safe up to your maximum IG of 32 V.

Sorry for missing this earlier.

Regards, Robert

TPS57060ENmax.xlsx

• Hello Robert,

Thanks for the updated spread sheet, as you mentioned I realize I forgot to take 10k internal resister into account.

I will also consider adding external serial resister.

Best regards,