IWRL6432AOP: IWRL6432AOP_DC-DC Applicability

Hi Kim,

The TPS62A02PDDCR/ TPS62A01PDDCR  do not have Spread Spectrum Clocking (SSC) and can affect EMI/EMC performance of the device. It is recommended to have SSC enabled for better emission performance. Also, lower switching frequency of 2.4 MHz is not recommended for mmWave applications. 

TPS6285020ADRLR , TPS6285020MDRLR with a higher controllable switching frequency and Spread Spectrum Clocking (SSC) would be recommended.

Regards

Ankit

Hi Kim,

Answering the first question,

1. The mark X here is a typo error. Both the pins are connected and brought out as Test Point 5.

2. The mode control circuit is not for the mmWave IC mode control but the Buck Converter. Any GPIO from mmWave IC (say REG_MODE_SELECT) shall control the circuit to switch between Forced PWM (MODE = 1) and PFM (MODE =0) during chirping and idle state respectively.

Regards

Ankit

Hi Kim,

1. Mode switching is not mandatory but recommended to optimize both better performance and lower power consumption.

2. Yes, you can use any one mode based on your use case application. When the MODE pin is set to a logic low level, the device operates in power save mode (PFM) at low output current and automatically transfers to fixed frequency PWM mode at higher output current. In PFM mode, the switching frequency decreases linearly based on the load to sustain high efficiency down to very low output current. With the MODE/SYNC pin set to high, the buck operates with pulse width modulation in continuous conduction mode (CCM). The switching frequency is defined by a resistor from the COMP pin to GND or by an external clock signal applied to the MODE/SYNC pin.

3. Auto PFM is best for lower power consumption while performance may not be the best as the witching frequency decreases linearly based on the load to sustain high efficiency down to very low output current. However, in Forced PWM mode, the radar has the best performance with constant switching frequency over the output current.

Regards

Ankit

Hi Kim,

Yes, you will either need to pull up or pull down that pin.

Regards

Ankit

Hi Kim,

It helps switch between Forced PWM and Auto PFM mode during chirping and deep sleep. This helps us get better performance at reasonable power i.e Forced PWM during chirping for best performance and Auto PFM during deep sleep for power conservation.

Regards

Ankit

Hi Kim,

In TI EVMs, we have implemented MOSFET based switch, and the GPIO drives the gate of the MOSFET. The MMIC GPIO is Push/Pull type configuration; and the buck mode is Open-Drain (considering required of external PU/PD circuit). Hence, connecting a push/pull signal to open-drain possess risk of increased leakage.

Regards

Ankit

Hi Kim,

That is one of the reasons as well. However, the mode pin can also be pulled up to 3.3V.

Regards

Ankit

Hi Kim,

You should be able to pull the mode in high by pulling it between VIN and 1.1V. Hence, if you pull it to 3.3V its should be in Forced PWM mode and if you are not looking for mode control you can remove the FET.

Regards

Ankit

Hello Kim,

I can confirm that the TPS628502 MODE pin signal can be controlled from a GPIO as long as the signal voltage is between 0V and TPS628502 VIN level. This also means the MODE signal should never set to high before VIN is applied to the TPS628502. (This is fulfilled with the MODE control with a FET.)

Best regards,

Andreas.

Hi Kim,

the point is that the FET circuit is connected to VIN voltage level via resistor and thus can not output a higher voltage than VIN.

Best regards,

Andreas.

Hello Kim,

it is OK to connect MMIC GPIO to the TPS628502 MODE pin. The MODE pin is a high impedance input and no open drain. The voltage level at this pin is relevant for mode selection.

Best regards,

Andreas.

Hello Kim,

the MODE/SYNC pin is an input.

Open drain architecture always refers to an output, because the drain of a transistor is the controlled signal and not a controlling signal.

So, MODE/SYNC pin is not open drain.

Usually digital inputs such as MODE/SYNC are using IC internally a Schmitt trigger with a high input impedance.

But Ankit was also right, the FET (Q3) together with the PU, which is used in the reference design, behaves like an open drain circuit.

Best regards,

Andreas.

Kim,

without a FET it is no open drain circuit.

From TPS628502 perspective it would be OK to connect MODE/SYNC to a MMIC GPIO.

Best regards,

Andreas.

Hi Kim,

Yes, it should be alright to connect Pull up to MMIC gpio.

Reagrds

Ankit