Power supply for CY7C65213

[NaMo_1534561]

Hello,

I have some questions about CY7C65213 power supply and UART pins.

1)Is it okay to apply a voltage to the RXD terminal when the VCCIO is powered on and the VCC is not powered on?

2)Which power supply is the internal oscillator of CY7C65213, VCC or VCCIO?
I would like to know if the internal CLK does not oscillate if no power is applied to VCC.

3)PINs (RI# / DSR# / DCD# / CTS#) are defined as input terminals. Can they be used in OPEN when not in use ?

Best regards,

Naoaki Morimoto

[Meghavi]

Hi, 

1) From the VCCIO is powered on and the VCC is not powered on, I understand USB-Serial Bridge Controller has a different power supply than the rest of the system. Please elaborate for what purpose you want to apply a voltage to the RXD terminal.

2) Yes it is correct. The internal oscillator has power supply from VCC.

3) Please refer Note 4 from the datasheet - "Any pin acting as an Input pin should not be left unconnected."

Regards

[NaMo_1534561]

Hi Meghavi-san,

Thank you for your reply.

I answer for your comment about 1).

"Due to the sequence specifications of the customer's power system, it is possible that the USB-Serial Bridge Controller will be supplied to VCCIO and the outside (RXD) before it is powered to VCC."

Best Regards,

Naoaki Morimoto

[NaMo_1534561]

Hi Meghavi-san,

I would like to confirm again about 3).

I understand that the GPIO pins when configured as input should not be left unconnected, but how about the RI# / DSR# / DCD# / CTS# pins for UART?

According to "the Table2. internal Flash Configuration" in the datasheet, it seems to connect internal pull-up for CTS# and DSR#.

Best Regards,

Naoaki Morimoto

[Meghavi · Accepted solution]

Hi Naoaki-san,

1) Ideally, there is no power up sequence of VCC and VCCIO. Very small delays in the order of nanoseconds (ns) do not matter. Powering up both the VCC and VCCIO together will work fine. It is also possible to have VCCIO present and connect VBUS later. Basically, this VCCIO will provide power to RXD pin. Can you please elaborate how much voltage do you require?

3) Please ignore my previous response about Q3. Please refer Note 5 - "Any GPIO, configured as “Input” should either be pulled high or low. A floating input pin (Tristate) has an indeterminate voltage level that can cause excess internal current consumption. A 10 kΩ pull-up or pull-down resistor is recommended on each of the input pin". 

This note applies for GPIO pins. UART pins in CY7C65213/CY7C65213A have internal pull-ups. So it can be left unconnected.

Regards

[NaMo_1534561]

Hi Meghavi-san,

Thank you for your confirmation. This query was solved by your answer.

Best regards,

Naoaki Morimoto