TPS57040-Q1: Max DUTY cycle

Kaji@PAN

Part Number: TPS57040-Q1

Hi,

I am looking for a DCDC for automotive use.
The specification is below.

VIN: 5.5 V to 18 V (40 V load dump)
VOUT: 5 V
IOUT: 30 mA typ, 60 mA max
SW frequency about 2 MHz (I want to operate at 2 MHz even at 30 mA)
The PeakLimit current should be lower, because VIN is a lead battery

I want to check if TPS 57040 - Q 1 meets specifications.
I understand that this device turns off when the voltage of the BOOT capacitor drops below 2.1V.
However, I do not know what the maximum duty cycle is.
In my specification, 91% DUTY is necessary.
Please tell me the maximum duty of this device.

Best Regards,

over 8 years ago

0 JohnTucker over 8 years ago

TI__Guru**** 191445 points

There is no specific maximum duty cycle for TPS57040-Q1. It can operate at +100% duty cycle as long as the BOOT voltage is greater than 2.1 V typical. See this app note for more details:
www.ti.com/.../slva547

0 Kaji@PAN over 8 years ago in reply to JohnTucker

Mastermind 7815 points

Thank you for your reply.
I confirmed the materials.
From the content of (4) in Table 2 of the document, I thought that the input voltage can operate normally up to 5.8 V at 5 V output. Is this idea correct?
Best Regards,

0 Kaji@PAN over 8 years ago in reply to Kaji@PAN

Mastermind 7815 points

I understood that the previous content was caused by discontinuous mode.
I confirmed the following statement in the data sheet.
It seems that the effective duty cycle is affected by the circuit.
If I increase the capacitance of the BOOT capacitor from 0.1 uF, will the effective duty cycle be high?
I'm sorry to ask a lot of questions, but I'd like to achieve VOUT = 5 V at VIN = 5.5V.

Best Regards,

Power management

Power management forum

TPS57040-Q1: Max DUTY cycle