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# DRV110: Several questions

Part Number: DRV110

Hi all

Would you mind if we ask DRV110?

<Question1>
We would like to confirm Cin "Input capacitor between VIN and GND".
The recomended value is 1.0uF upto 4.7uF.
The customer would like to configure as follows;

-Ihold : 100mA
-IPeak : 500mA
-Vs : 55V
-> We will confirm each constant(RPEAK, RHOLD and RSENSE).

They could not configure Ihold=100mA, actual value was 200mA.
With increasing VS, Ihold value was increased, is it correct operation?
And then, with out Cin, Ihold was 120mA. Does Ihold depends on Cin?
What is Cin used for? For ripple rejection?
Should Cin be between 1.0uF and 4.7uF?

<Question2>
We would like to know Equation2 and Equation3 correctly.
What is 66.67khom calculated?
We would like to calculate Vref, so could you share us formula for it?

Kind regards,

Hirotaka Matsumoto

• Hi all

We add follows;

ROSC=0ohm
Rs=15khom
C1=1uF
Ckeep=0.068uF
Rpeak=120kohm
Rhold=100kohm
Rsense=1ohm

Kind regards,

Hirotaka Matsumoto

• Hello,

Based on your target Ipeak and Ihold, Rpeak=120kohm and Rhold=100kohm with Rsense=1ohm
Ihold and Ipeak it is not affected by Cin, Cin is a main supply de-coupling capacitor. The current limiting resistor and Cin will set
the turn on voltage ramp up. In order not to slow down too much the ramp up voltage and DRV110 Vin Cin=1uF is recommended if the external supply is not too noisy.
The 66.67kohm is not calculated it is an internal design parameter. The voltage reference it is adjustable if Rpeak and Rhold are greater than 66.67kohm, this voltage threshold divided by Rsense sets Ipeak and Ihold.

Regards,
Costin
• In reply to Costin Cazana:

Costin san

Thank you so much for your reply!

We got what Cin is used for.
However, we could not understand how we should calculate Rpeak value and Rhold value from Ipeak=500mA and Ihold=100mA.
There are Equation2 and Equation3 on the data sheet. For example, we would like to configure Ipeak=500mA and Ihold=100mA, how should we caluculate for Rpeak and Rhold?
There is no Vref value.
So, in order to configure Ipeak=500mA and Ihold=100mA,  are Rpeak=120kohm and Rhold=100kohm(customer's setting) suitable value?

Kind regards,

Hirotaka Matsumoto

• In reply to Hirotaka Matsumoto:

Matsumoto san,

If Rsesnse=1ohm

Rpeak(kohm)= (0.9*66.67)/0.5 that's 120kohm

Rhold(kohm)=(0.15*66.67)/0.1 that's 100kohm

Regards,
Costin
• In reply to Costin Cazana:

Costin san

Thank you so much for your prompt reply!

OK, we got that customer's settings are correct.

We have some questions that there is the difference between customer's measured Ihold current value and calculation Ihold current value.
In spite of Rhold = 100khom, customer's measured Ihold current value was 200mA.
So, if you have some advice, could you let us know?
What does Ihold depends on? Only Rhold?

Kind regards,

Hirotaka Matsumoto

• In reply to Costin Cazana:

Costin san

Thank you so much for your DRV110's support always!
We would like to send you detail information, waveform of the coil inductor and hold pin's voltage using E2E private message..
So, could you accept friend request?

Kind regards,

Hirotaka Matsumoto

• In reply to Hirotaka Matsumoto:

Matsumoto san,

Rhold sets the Ihold , internally sets the Ref voltage.
In normal condition with 1 ohm sense resistor can not get to 200mA Ihold.
I accepted the request but I think it will be easier to e-mail me directly at:
costin.cazana@ti.com

Regards,
Costin

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