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Smart Bluetooth

Anonymous
Not applicable

Is there an internal  weak pulldown resistor on pin 13 of 20737 ? That is UART RX and this pin also is used to start in either app or debug mode. Low level on this pin means app mode and that is why there is a resistor on TAG3 - R3 (10K).

Can I omit this resistor in my design ? I think there should be already an internal one ?

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1 Solution
ShawnA_01
Employee

Although the TAG3 schematics (uses chip on board versus a module) shown in the Hardware Users Manual includes a 10k Pulldown resistor (marked R3), the internal 20737S module schematics shows one already present (marked R12).   I've looked at both the 20732S and 20736/7S internals.

Furthermore, the 20736/7S Technical Reference Manual states UART_RX (Pin 18 of the module) is pulled low internally.

You asked about the 20737 (chip), not the 20737S (module), so I conclude there is NO pulldown on the chip, or they would not have added one to the module.   If you're doing chip on board design, you need the resistor.

Note:  In your original text you state "Pin 13 of 20737 is UART_RX".   I believe you meant Pin 12 is UART_RXD, as the HWUM shows Pin 13 as UART_TXD.

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1 Reply
ShawnA_01
Employee

Although the TAG3 schematics (uses chip on board versus a module) shown in the Hardware Users Manual includes a 10k Pulldown resistor (marked R3), the internal 20737S module schematics shows one already present (marked R12).   I've looked at both the 20732S and 20736/7S internals.

Furthermore, the 20736/7S Technical Reference Manual states UART_RX (Pin 18 of the module) is pulled low internally.

You asked about the 20737 (chip), not the 20737S (module), so I conclude there is NO pulldown on the chip, or they would not have added one to the module.   If you're doing chip on board design, you need the resistor.

Note:  In your original text you state "Pin 13 of 20737 is UART_RX".   I believe you meant Pin 12 is UART_RXD, as the HWUM shows Pin 13 as UART_TXD.

View solution in original post