LM74700-Q1: LM74700-Q1

Kiran Ajjevadimath

Part Number: LM74700-Q1
Other Parts Discussed in Thread: LM74502H, LM74900, LM74912, LM74502

Tool/software:

HI,

We would like to use LM74700-Q1 with a PWM signal to turn ON and OFF Mosfet continuously at a specified frequency.

Could you please let us know what is the Turn ON and Turn OFF time so we could decide on frequency of PWM signal to Enable pin.

Thanks.

Kiran A

4 months ago

0 Shiven Dhir 4 months ago

TI__Mastermind 48475 points

Hi Kiran,

I assume you are planning to use EN signal for ON/OFF PWM.

Can you help me understand what is the application of doing so? Since the body diode is still present, the power path will not be disconnected.

Regards,

Shiven Dhir

0 Kiran Ajjevadimath 4 months ago in reply to Shiven Dhir

Prodigy 120 points

I would like to use it for a LED driver testing. Below is the requirement

0 Shiven Dhir 4 months ago in reply to Kiran Ajjevadimath

TI__Mastermind 48475 points

Hi Kiran,

What will be the slew rate and voltage level of PWM?

Regards,

Shiven Dhir

0 Kiran Ajjevadimath 4 months ago in reply to Shiven Dhir

Prodigy 120 points

Hi,

Voltage level will be within the supported range of LM74700(around 12V).

Slew rate we don't have specific requirement; we are fine with the supported slew rate of LM74700.

0 Shiven Dhir 4 months ago in reply to Kiran Ajjevadimath

TI__Mastermind 48475 points

Hi Kiran,

PWM till 100Hz should be fine.

Regards,

Shiven Dhir

0 Kiran Ajjevadimath 4 months ago in reply to Shiven Dhir

Prodigy 120 points

Just to confirm, any frequency above 100Hz, the diode controller will not be able to respond?

0 Shiven Dhir 4 months ago in reply to Kiran Ajjevadimath

TI__Mastermind 48475 points

Hi Kiran,

The controller will be able to respond but its charge pump needs time to charge. If we use higher frequency, there is a chance that charge pump is not charged and we disable the power supply again.

You can consider LM74502H and use its OV pin to disable the power path if you need very high PWM capability.

Regards,

Shiven Dhir

0 Kiran Ajjevadimath 4 months ago in reply to Shiven Dhir

Prodigy 120 points

HI Shiven,

Thanks for suggestion. LM74502H works for PWM requirement.

Since OV shuts off external Mosfet for any voltage above 1.25V at OV pin, this calls for an inverting logic (If output needs to be in sync with input).

Is there any IC with "under voltage" detection pin so we can directly tie it to Input voltage and output will be in sync with input PWM signal.

0 Shiven Dhir 4 months ago in reply to Kiran Ajjevadimath

TI__Mastermind 48475 points

Hi Kiran,

You can consider using LM74900 or LM74912 but might be an overkill.

Regards,

Shiven Dhir

0 Kiran Ajjevadimath 4 months ago in reply to Shiven Dhir

Prodigy 120 points

Thanks Shiven.

Are there Pspice working model for LM74502 & LM74900, the one downloaded from Ti Website pops out below error while importing to TINA.

LM74502

LM74900:

+1 Shiven Dhir 4 months ago in reply to Kiran Ajjevadimath

TI__Mastermind 48475 points

Hi Kiran,

You can use Pspice for TI for LM74502.

For LM74900, it only works on ORcad Pspice.

Regards,

Shiven Dhir

Power management

Power management forum

LM74700-Q1: LM74700-Q1