Question: The AD7124-4/8 standard grade, AD7124-4/8 B-grade, and AD7124-8 W-grade were re-designed? Where can I find details on the changes to the part performance/functionality?
When a product is re-designed or production flow (fabrication site, assembly site) is changed, a Product/Process Change Notice (PCN) is issued which documents the changes done to the product. For the standard grade AD7124-4/AD7124-8 (LFCSP package only), the details of the changes are listed in PCN_22_0096.
Product/Process Change Notice: ADI_PCN_22_0096_Rev_-_Form.pdf (analog.com)
Details of the changes to the AD7124-4/8 B-grade material and AD7124-8 W-grade can be found in PCN_21_0248.
Product/Process Change Notice: ADI_PCN_21_0248_Rev_B_Form.pdf (analog.com)
The AD7124-4 in TSSOP was also re-designed and any changes to functionality/performance are detailed in PCN_22_0234.
Product/Process Change Notice: ADI_PCN_22_0234_Rev_A_Form.pdf (analog.com)
Question: How can I identify which revision of the die I am using?
The standard AD7124-4 has an ID value of 0x04 while the AD7124-4 B-grade has an ID value of 0x06. The re-designed die has an ID value of 0x07 for both the standard part and the B-grade part.The AD7124-8 standard part has an ID of 0x14 and the AD7124-8 B-grade and W-grade have an ID value of 0x16. The re-designed die for the standard part, B-grade or W-grade has an ID of 0x17.
Also, the PCN lists the change over datecodes for the re-design.
Question: What are the differences between the standard AD7124-4/8, B-grade AD7124-4/8 and the AD7124-8 W-grade?
Answer: If you have the new silicon revision, you may refer to the updated Table 1 of the AD7124-4 (Rev.E) and AD7124-8 (Rev.F) datasheet. The only differences are the internal reference temperature coefficient and the height of the LFCSP package.
However, if you have the old silicon revision, there are some key differences between the B-Grade (AD7124-xBBCPZ/AD7124-xBBCPZ-RL) and the standard (AD7124-xBCPZ/AD7124-xBCPZ-RL) AD7124-4/8. The part to use will depend on your application requirements.
Differences include:
- Package
- Reference TempCo Specification
- Multichannel Measurement (channel sequencing) settling time (at Gain=1)
- Excitation currents status/mode in standby mode
- Gain Registers value when MCLK & SCLK are Asynchronous
Package:
- The B-grade and W-grade are available in the LFCSP package only whereas the standard is available in both TSSOP (AD7124-4 only) and LFCSP. The LFCSP package is 5 x 5 mm package for B-grade, W-grade, and standard but the height is the key difference, where the B-grade and W-grade height is 0.95 mm and the standard is 0.75mm.
Reference TempCo:
- The B-grade AD7124-4/8 internal reference has a tempco of 10 ppm/’C max. The internal reference on the W-grade and standard silicon (LFCSP) has a temp of 15 ppm/’C max.
Multichannel settling time (at G=1):
- The standard silicon, when used in multi-channel mode, does not settle within the allowed time when switching channels for gains of 1 when high output data rates are used in conjunction with large resistive loads. The B-grade silicon includes a pre-charge buffer which aids the settling and hence ensures that all conversions are fully settled within the allowed time.
- The re-designed silicon for all parts includes a pre-charge buffer which ensures that the first conversion after switching channels is settled.
Excitation currents status in standby mode:
- On the standard silicon (LFCSP and TSSOP), the excitation currents are disabled when the ADC is placed in standby mode. On the B-grade, the excitation currents can remain active in standby mode. This is useful when current consumption minimization is not important. Some customers use single conversion mode as a timing mechanism to provide conversions within timeslots. In this use case, keeping the excitation currents enabled during standby mode minimizes the power up time.
- On the re-designed silicon for all parts, the excitation currents, if enabled, remain active in standby mode.
- Also, for all parts, an additional excitation current of 100 nA is included on the part. Setting the Excitation Current bits to b111 enables the 100nA current.
Gain Registers value when MCLK & SCLK are Asynchronous
- On the standard silicon, the gain register can reset to its default value periodically if SCLK and MCLK are asynchronous. So, if internal FS calibrations or system FS calibrations are performed in a system where SCLK and MCLK are asynchronous, the gain register should be read periodically to ensure that it has not reset. On the B-grade, the gain register does not reset even when SCLK and MCLK are asynchronous.
- On the re-designed silicon for all parts, the gain register does not reset even when SCLK and MCLK are asynchronous.
Question: Is the B-grade better than the standard AD7124-4/8 and W-grade?
Answer: Yes, the B-grade is better than the standard and W-grade. For full details on the differences see above. However, the W-grade is automotive qualified so it is the recommended part to use for automotive applications.
Question: Should I use the standard silicon, the B-grade, or the W-grade?
Answer: For any new design, the B-grade is recommended especially if a good internal drift is required. For full details on the differences see above.
Question: How can I tell that the model part is a standard silicon, B-grade, or W-grade?
Answer: When ordering there are three options available, AD7124-4BBCPZ/AD7124-8BBCPZ-RL, AD7124-4BCPZ/AD7124-8BCPZ-RL, and AD7124-8WBBCPZ-RL7. The extra B in the first option represents the B-grade, and the extra WB in the last option represents the W-grade.
