MP6543: Stealing current from the charge pump output (Vcp) and MP6543 questions

Motor Drivers/Sensors
#1

Any possibility of stealing some current from the Vcp to run other circuits?

I need ~50mA on V3P3. So, can I:

  1. Connect VIN_LDO to VCP?
  2. Connect VIN_LDO to VCP through a switcher (to reduce the current)?
    Something like the MPM3606 low current switcher…

I’m sure the amount of current I can steal is a function of the switching frequency of the PWM into the MP6543…

Other questions:
A. What is the PWM frequency VS power consumption?
B. What is the maximum PWM frequency?
C. What is the drop out voltage and PSRR for the V3P3 regulator?
D. If I cannot steal 50mA, how much can I steal?

I have multiple MP6543’s on the board, so, perhaps I can load share.

Thanks!

#2

Hello harjit,

I apologize for the delay, I will try to get a response back to you in 2 days.

Thank you,
Vinh Tran

#3

Hello Harjit,

VCP is an output, do not connect anything to it. V3P3 can support 100mA. You can use that to power your MCU or low current device.

A. We don’t have such documentation. This is dependent on operating conditions.
B. ~250kHz with 2% DC
C. We don’t have such documentation.
D. VIN_LDO can support up to 100mA.

Thank you,
Vinh Tran

#4

Thank you for the information.

Can Monolithic Power consider providing the output current limit for VCP?

The thinking is - since VCP is used to drive the gate of the high side switches, the current it can support is designed based on 250kHz switching frequency and the high side FET gate capacitance. So, if the switching frequency is lower, there will be current one can “steal” from VCP. In my case, the switching frequency will be approx. 100kHz. So, this means around 50% of the design current for VCP should be available.

Regards.

#5

Hello harjit,

You can try to “steal” current from VCP. However, because it is used to drive the HS FETs, you may see improper switching.

Is there a reason you can’t use V3P3?

Thanks,
Vinh Tran

#6

I need 3.3V and I would like to use 1 LiPo cell (3V to 4.2V).

So, I was thinking, use the VCP to boost the 1 LiPo cell (should be double of input so, 6V to 8.4V). Feed that into the LDO’s input and then use the clean 3.3V output.