Hello guys,
One of my customers is evaluating PGA308 on their own board for their new products.
They want to read "CFG2" RAM data out from DOUT pin (No.1) using "1W" pin.
Could you please tell me how to read the data out?
Your reply would be much appreciated.
Best regards,
Kazuya.
Hi Kazuya,
I understand you want to read data from the PGA308 CFG2 register using custom board.
The PGA308 uses a one-wire communication protocol, where both the PGA308 register data and the read/write command data from your controller will be sent on the 1W pin.
The Dout/Vclamp pin can be configured as a push/pull digital output (Dout Mode) by bit [D8] of the CFG2 register. In Dout Mode, the Dout pin can be driven logic high or logic low by bit [D7] of the CFG2 register. This function is similar to a digital general purpose output (GPO) pin and does not send serial register data.
You may send and receive PGA308 register data using the 1W pin and one-wire communication protocol as described in section 4 (Detailed Digital Description) of the PGA308 User's Guide.
Regards,
Zach
Hi Kazuya-san,
A couple of additional comments Regarding the One-Wire protocol:
As Zach has mentioned, Figure 4-2 and Figure 4-3 on Section 4.4 Digital Interface of the PGA308 User Guide explains the One-Wire protocol used on the 1W to communicate with the PGA308 on page 54.
All communication transactions start with an initialization byte (55h) transmitted by the external controller. The second byte is the command byte (Figure 4-3).
On the Command Byte, the MSB is the R/W bit. Use MSB='1' indicating a read command. The next bit is the B/R bit. Use B/R = '0' for RAM access. Table 7-21 on p.88 shows the OTP and RAM register overview. To read the CFG2 RAM register use P[5:0]: 000100.
Refer to Figure 5-8 for the PGA308 read algorithm on page 64 for more details.
Please keep in mind, it is important to access the One-wire while the interface is active. Depending on the standalone configuration and how the OTPs have been programmed, and the programmed OWD register settings, the one-wire may time out shortly after power-up. This is especially true in three-terminal modules where the 1W pin is connected directly to VOUT. Read in detail section 5.5 'Standalone Mode' and 'software lock mode', and refer to the details of figure 5-10 standalone algorithm.
Thank you and Regards,
Luis
H Kazuya-san,
To answer the Customer question:
What is this function for? Is it just used as a general purpose output port?
Yes, the Customer is correct. When configured as DOUT, the pin is used for general purpose static high /static low digital pin. The original intent during the PGA308 product definition was to use the DOUT pin to control an external analog switch, so that the same PGA308 hardware module could be re-configured as either a voltage output or current output in the hardware, using an external analog switch to change the circuit configuration.
Please refer to this previous E2E post regarding DOUT function:
However, in the majority of cases, Customer's use the VCLAMP/DOUT pin configured as VCLAMP pin to limit the output voltage, and avoid damaging a lower voltage input ADC during a fault condition. See detailed below explanation of VCLAMP functionality from the PGA308 User's Guide on page 44:
Thank you,
Kind Regards,
Luis
