[FAQ] AM62L, AM64x Custom board hardware design – ADC0 design guidelines

Hi Board designers, 

Thank you for the query.

AM64x

1. Supported ADC resolution and channels

The processor family supports 1 × 12-bit ADC, up to 4 MSPS, and 8 multiplexed analog inputs. See the device-specific silicon errata (advisory i2287) for guidance on using SR2.0 processor on existing board or recommendations for a new custom board design. For more details, see the General Connectivity Peripherals section in the Peripherals chapter of the devicespecific TRM. Note that the processor family ADC inputs are not fail-safe. Do not apply external inputs before the processor supplies ramps.

2. Guidelines for using ADC peripheral

See the device-specific silicon errata (advisory i2287) for guidance on using SR2.0 processor on existing board or recommendations for a new custom board design.

 Note that the processor family ADC inputs are not fail-safe. Do not apply external inputs before the processor supplies ramps and are stable.

Refer pin Pin Connectivity Requirements section for connecting the ADC inputs when complete ADC is not used or any of the ADC inputs are not used 

3.ADC0 input range 

The ADC0 module supports the below ADC reference pins

ADC0_REFN -   ADC0 Negative Reference J16
ADC0_REFP  -  ADC0 Positive Reference J15

Additionally the ADC0 modules includes VDDA_ADC0 ADC0 analog supply

ADC12B Electrical Characteristics describes the allowed range ADC range VADC0_VREFP and VADC0_VREFN

4.ADC inputs used as GPI 

The ADC inputs are connected to the AM64x GPIO1 module when configured to operate as general-purpose inputs (GPI). The assignment of each ADC0 pin to the GPIO1 module is defined in the ADC0 Signal Description table found in the datasheet.

These inputs are able to perform the same input function as any other GPIO1 input. Please read the GPIO sections in the TRM to understand the capabilities of these inputs.

AM62L 

1. Supported ADC resolution and channels

1x 12-bit Analog-to-Digital Converter (ADC)
– 10 bits of effective resolution (ENOB ≅ 10)
– Up to 4MSPS
– 4x analog inputs (time-multiplexed)

2. Guidelines for using ADC peripheral

Note that the processor family ADC inputs are not fail-safe. Do not apply external inputs before the processor supplies ramps and are stable.

Refer pin Pin Connectivity Requirements section for connecting the ADC inputs when complete ADC is not used or any of the ADC inputs are not used

3.ADC0 input range 

VADC0_VREFP Positive Reference Voltage = VDDA_ADC0

VADC0_VREFN Negative Reference Voltage = VSS

The ADC0 module does not support separate VADC0_VREFP and VADC0_VREFN pins 

4.ADC inputs used as GPI 

Not supported 

Regards,

Sreenivasa

Hi Board designers, 

Additional information on AM64x input range 

(34) AM6422: External Analog Reference for ADC0 - Processors forum - Processors - TI E2E support forums

https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1304300/faq-am6442-adc0_dig_test-0-7-when-a-digital-inputs-can-these-eight-be-considered-as-main-gpio-and-or-interrupt-inputs-at-1-8v-logic

External Analog Reference for ADC0

https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1433807/am6422-external-analog-reference-for-adc0/5499688#5499688

AM6442: Configuring AM6442 ADC0 pins as GPI.

https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1498583/am6442-configuring-am6442-adc0-pins-as-gpi

 Overvoltage at ADC input

TI expects the system designer to design their product to operate withing the Recommended Operating Condition (ROC) limits, not the Absolute Maximum Rating limits. See table note #1 associated with the Absolute Maximum Rating table.

Operation outside the Absolute Maximum Ratings may cause permanent device damage. Absolute Maximum Ratings do not imply functional operation of the device at these or any other conditions beyond those listed under Recommended Operating Conditions. If used outside the Section 6.4, Recommended Operating Conditions but within the Absolute Maximum Ratings, the device may not be fully functional, and this may affect device reliability, functionality, performance, and shorten the device lifetime.

You should not be using the limits defined in the Absolute Maximum Rating table for designing normal operating conditions. Applying a potential outside of the ROC limits has a chance of damaging the AM64x device. The ROC max for VDDA_ADC0 is 1.89V and the ROC max for any AIN[7:0] is the same potential that is applied to VDDA_ADC0. There is a chance you will damage the device if you exceed these ROC limits for any period of time. 

AM64x has internal ESD clamp diodes on each of the AIN[7:0] pins. These internal clamps must be considered because they turn on when the applied voltage exceeds the limits defined in the "Steady-state max voltage at all other IO pins" parameter defined in the Absolute Maximum Rating table.

Note: The internal ESD protection circuits were only designed to protect the device during handling, before and during PCB assembly. These clamps are not capable of protecting the device from system-level ESD events, which can have much higher energy levels that what is encountered during device handling. Therefore, the system designer is expected to use external ESD protection circuits if it necessary to protect AM64x from system-level ESD events.

The device IBIS model should represent what you can expect to see when looking into one of the ADC AIN[7:0] pins.

AM2434: AM24x ADC0 Measurement at AIN7

https://e2e.ti.com/support/microcontrollers/arm-based-microcontrollers-group/arm-based-microcontrollers/f/arm-based-microcontrollers-forum/1500190/am2434-am24x-adc0-measurement-at-ain7

Regards,

Sreenivasa