Analog Comparator Controller (ACC) SAMx

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Analog Comparator Controller (ACC) SAMx Block The ACC SAMx block configures the Analog Comparator Controller peripheral on SAM E70/S70/V71 devices. This block compares two analog signals and outputs a digital result, with optional DAC integration for programmable threshold comparison.

Block Inputs/Outputs

Inputs: Dynamic based on configuration

Outputs: Dynamic based on configuration

Dynamic Port Configuration

• DACC Input appears when DAC0 or DAC1 is selected as the minus input (SELMINUS)
• Comparator Output and Comparator Edge Output are individually configurable as block outputs

Block Input/Output Datatype

Supported Device Families

Note: This block is specifically for SAMx7 devices with ACC and DACC peripherals. Other SAM families (E5x, C2x, D2x) use different comparator architectures.

Block Parameters

Comparator Operation

Signal Sources

Positive Input (SELPLUS):

• AFE0 channels: AD0-AD5 (mapped to specific pins)
• AFE1 channels: AD0-AD1 (mapped to specific pins)

Negative Input (SELMINUS):

• Internal Temperature Sensor output
• VREFP (voltage reference)
• DAC0 or DAC1 (programmable threshold)
• AFE0 channels: AD0-AD3 (external reference)

Hysteresis

Hysteresis prevents output oscillation when input signals are near the threshold:

Edge Detection

The EDGETYP parameter configures which edges trigger events:

DAC Integration

When DAC0 or DAC1 is selected as SELMINUS, the block automatically:

1. Enables the DACC peripheral
2. Configures the DAC clock prescaler
3. Sets up the selected DAC channel
4. Creates a block input for dynamic threshold control

DAC Input Scaling

Implementation Details

Register Configuration

Peripheral Clock

The block automatically enables peripheral clocks using PMC_PCER registers based on peripheral IDs for both ACC and DACC modules.

Usage Examples

Example 1: Voltage Threshold Detection

Compare an analog input against a fixed DAC threshold:

Configuration:
- SELPLUS: AFE0_AD0 (external analog signal)
- SELMINUS: DAC0 (threshold)
- DACC Initial Output: 2048 (1.65V threshold)
- BlockInput DACC_INPUT: is not a block input (fixed threshold)
- Comparator Output: is a boolean block output

Result: Output is HIGH when input voltage > 1.65V

Example 2: Dynamic Threshold with PWM Fault

Programmable threshold with fault generation for motor control:

Configuration:
- SELPLUS: AFE0_AD2 (current sense)
- SELMINUS: DAC1 (overcurrent threshold)
- BlockInput DACC_INPUT: is a 16 bits unsigned block input
- FAULT: Defined by Comparator Output
- EDGETYP: Rising

Result: PWM fault generated when current exceeds DAC-programmed threshold

Example 3: Temperature Monitoring

Compare external sensor against internal temperature reference:

Configuration:
- SELPLUS: AFE0_AD3 (external thermistor)
- SELMINUS: Temperature Sensor (TS) Output Voltage
- HYST: 25 mV
- Comparator Output: is a boolean block output

Result: Output indicates relative temperature comparison

Troubleshooting

Comparator Not Responding

Problem: Comparator output doesn’t change with input.

Solutions:

• Verify input pin selection matches physical connections
• Check that input voltage is within ADC range (0-3.3V)
• Ensure peripheral clock is enabled (check for PMC errors)

DAC Output Incorrect

Problem: DAC threshold voltage is wrong.

Solutions:

• Verify DACC Initial Output value is in correct range (0-4095 for 16-bit)
• Check input scaling mode matches your signal type
• DAC saturation (DACC_SAT) may be limiting the output

Noisy Output Toggling

Problem: Comparator output oscillates rapidly.

Solutions:

• Enable hysteresis (25 mV or 45 mV)
• Add external filtering on analog input
• Ensure reference (DAC) is stable

PWM Fault Not Generated

Problem: FAULT setting enabled but PWM doesn’t respond.

Solutions:

• Verify PWM block has fault input enabled
• Check EDGETYP matches expected fault condition
• Confirm SELFS setting for fault source selection

See Also

• ADC SAMx7 (AFEC)
• DAC SAMx
• High-Speed Analog Comparator (dsPIC)
• PWM SAMx7