SNLA386 May 2021 DS250DF810 , DS280DF810

2 Reading Junction Temperature Procedure

Table 2-1 provides a programming procedure to read the junction temperature from the DS2X0DF810 25-28G retimers. This procedure is beneficial for occasional debug and link monitoring.

Note: The accuracy of the on-die temperature sensor is not ensured by production testing. Through empirical observation, the temperature sensor readback exhibits a typical T_J accuracy of approximately ±7°C. Therefore, the procedure should be restricted to occasional debug use only.

Table 2-1 Programming Procedure for Reading Junction Temperature

STEP	REGISTER SET	OPERATION	REGISTER ADDRESS [HEX]	REGISTER VALUE [HEX]	WRITE MASK [HEX]	COMMENT
Normal Retimer configuration
Perform all steps to configure the Retimer as normal. Junction temperature measurements are the most useful when the device is operating in a configuration which mimics the mission-mode configuration.
Configure Retimer for temperature readback
1	Shared	Write	FF	10	FF	Select Channel 0 – Channel 3 shared registers
2	Shared	Write	04	40	40	Reset Channel 0 – Channel 3 shared registers
3	Shared	Write	FF	20	FF	Select Channel 4 – Channel 7 shared registers
4	Shared	Write	04	40	40	Reset Channel 4 – Channel 7 shared registers
5	Shared	Write	FF	10	FF	Select Channel 0 – Channel 3 shared registers
6	Shared	Write	0F	00	FF	Enable temperature detection CH0-CH3
7	Shared	Write	FF	20	FF	Select Channel 4 – Channel 7 shared registers
8	Shared	Write	0F	00	FF	Enable temperature detection CH4-CH7
9	Shared	Write	FF	01	FF	Disable broadcast write to all channels, read from channel selected in Shared Reg_0xFC
10	Shared	Write	FC	04	0F	Select single channel
11	Channel	Write	19	01	C1	Enable channel temperature detection
12	Channel	Write	18	01	03	Enable channel temperature detection
13	Shared	Write	FF	10	FF	Select Channel 0 – Channel 3 shared registers
14	Shared	Write	0C	00	38	Configure the input to the analog-to-digital converter (ADC)
15	Shared	Write	0C	02	03	Enable ADC
16	Shared	Write	0C	04	04	Reset ADC
17	Shared	Write	0C	00	04	Set ADC to capture Analog Voltage
18	Wait 200 μs
19	Shared	Write	0C	00	02	Disable ADC to freeze value
Temperature readback
20	Shared	Read	0D	--	--	D_SAR[7:0] = Reg_0x0E[7:0]
21	Shared	Read	0E	--	--	D_SAR[9:8] = Reg_0x0E[1:0]
*Decimal_representation_of_temperature_code* = (Reg_0x0E and 0x03) × 256 + Reg_0x0D T_J = (0.73 × *Decimal_representation_of_temperature_code) – 340, in degrees C Note:* The numbers 256 and 340 in the previous equations are decimal numbers.
22	Shared	Write	FF	10	FF	Select Channel 0 – Channel 3 shared registers
23	Shared	Write	04	40	40	Reset Channel 0 – Channel 3 shared registers
24	Shared	Write	FF	20	FF	Select Channel 4 – Channel 7 shared registers
25	Shared	Write	04	40	40	Reset Channel 4 – Channel 7 shared registers
26	Shared	Write	FF	01	FF	Enable read/write from/to channel selected in Reg_0xFC
27	Shared	Write	FC	04	0F	Select single channel
28	Channel	Write	19	00	C1	Disable channel temperature detection
29	Channel	Write	18	00	03	Disable channel temperature detection