Channel Relationship
each channel is NOT a separate device, but they do operate independently within the same chip.
One Chip, Four Independent Channels
The ADC12QJ1600-EP is a single physical IC in a single 144-ball BGA package. Inside that one chip, there are four ADC cores (A, B, C, D). Think of it like four workers sharing the same office building — they each do their own job independently, but they share the building's infrastructure.
What Is Shared (the "building")
| Shared Resource | Why |
|---|---|
| CLK± input pins | One clock input drives all four cores simultaneously |
| SYSREF± input | One synchronization signal for all channels |
| SPI interface (SCLK, SCS, SDI, SDO) | One serial bus configures the whole device |
| Internal PLL / VCO | One clock generator for the whole chip |
| JESD204C SerDes lanes (D0–D7) | All channels share the output lane pool |
| Power supplies (VA11, VA19, VD11...) | All channels share the same supply pins |
| SYNCSE pin | One SYNC signal for JESD link initialization |
What Is Independent (the "workers")
| Independent Resource | Meaning |
|---|---|
| Analog input pins (INA±, INB±, INC±, IND±) | Each channel connects to a completely different signal source |
| ADC core | Each channel has its own sample-and-hold and conversion logic |
Full-scale range (FS_RANGE_A/B/C/D) | Each channel can be tuned to a different input amplitude |
Offset correction (OFS_A/B/C/D) | Each channel has its own DC offset trim |
| Overrange flag (ORA, ORB, ORC, ORD) | Each channel independently detects clipping |
| Calibration state | Each core is calibrated individually |
A Concrete Mental Model
Think of it this way:
┌─────────────────────────────────────────────────────┐
│ ADC12QJ1600-EP (one chip) │
│ │
│ Signal 1 ──► [ADC Core A] ──┐ │
│ Signal 2 ──► [ADC Core B] ──┤ │
│ Signal 3 ──► [ADC Core C] ──┼──► JESD204C ──► FPGA │
│ Signal 4 ──► [ADC Core D] ──┘ │
│ ▲ │
│ shared CLK± │
└─────────────────────────────────────────────────────┘
Each core converts a different analog signal at the same moment (same clock edge). The four resulting digital samples are then packaged together and sent to the FPGA over the shared JESD204C lanes.
So to Directly Answer Your Question
| Question | Answer |
|---|---|
| Is each channel a separate physical chip? | No. All four channels are inside one BGA package. |
| Do the channels operate at the same time? | Yes. All four sample simultaneously on the same CLK± edge. |
| Can each channel receive a different signal? | Yes. INA±, INB±, INC±, IND± are four separate input pairs. |
| Can each channel be configured differently? | Partially. Gain and offset are per-channel, but clock, JMODE, and JESD settings apply to the whole device. |
| Is there any crosstalk between channels? | Very little. The non-interleaved architecture and differential inputs minimize inter-channel interference, but they are on the same silicon so there is some finite coupling — the datasheet specifies a crosstalk figure. |
Contrast: What a "Separate Device" Would Look Like
If you needed truly isolated channels — for example, in a safety-critical system requiring galvanic isolation, or a system needing different sample rates per channel — you would use multiple separate ADC chips. The ADC12QJ1600-EP does not support that; all four channels must run at the same sample rate using the same clock.