COMP — Comparator

The comparator (COMP) compares an input voltage (VIN+) against a second input voltage (VIN-). VIN+ can be derived from an analog input pin (AIN0-AIN7). VIN- can be derived from multiple sources depending on the operation mode of the comparator.

The main features of COMP are the following:

  • Input range from 0 V to VDD
  • Single-ended mode
    • Fully flexible hysteresis using a 64-level reference ladder
  • Differential mode
    • Configurable hysteresis
  • Reference inputs (VREF):
    • VDD
    • External reference from AIN0 to AIN7 (between 0 V and VDD)
    • Internal references 1.2 V, 1.8 V, and 2.4 V
  • Three speed/power consumption modes:
    • Low-power
    • Normal
    • High-speed
  • Single-pin capacitive sensor support
  • Event generation on output changes
    • UP event on VIN- > VIN+
    • DOWN event on VIN- < VIN+
    • CROSS event on VIN+ and VIN- crossing
    • READY event on core and internal reference (if used) ready
Figure 1. Comparator overview

Diagram: Comparator overview

Once enabled (using the ENABLE register), the comparator is started by triggering the START task and stopped by triggering the STOP task. The comparator will generate a READY event to indicate when it is ready for use and the output is correct. The delay between START and READY is tINT_REF,START if an internal reference is selected, or t COMP,START if an external reference is used. When the COMP module is started, events will be generated every time VIN+ crosses VIN-.

Operation modes

The comparator can be configured to operate in two main operation modes: differential mode and single-ended mode. See the MODE register for more information. In both operation modes, the comparator can operate in different speed and power consumption modes (low-power, normal and high-speed). High-speed mode will consume more power compared to low-power mode, and low-power mode will result in slower response time compared to high-speed mode.

Use the PSEL register to select any of the AIN0-AIN7 pins as VIN+ input, regardless of the operation mode selected for the comparator. The source of VIN- depends on which of the following operation mode are used:

  • Differential mode - Derived directly from AIN0 to AIN7
  • Single-ended mode - Derived from VREF. VREF can be derived from VDD, AIN0-AIN7 or internal 1.2 V, 1.8 V and 2.4 V references.

The selected analog pins will be acquired by the comparator once it is enabled.

An optional hysteresis on VIN+ and VIN- can be enabled when the module is used in differential mode through the HYST register. In single-ended mode, VUP and VDOWN thresholds can be set to implement a hysteresis using the reference ladder (see Comparator in single-ended mode ). This hysteresis is in the order of magnitude of VDIFFHYST, and shall prevent noise on the signal to create unwanted events. See Hysteresis example where VIN+ starts below VUP for an illustration of the effect of an active hysteresis on a noisy input signal.

An upward crossing will generate an UP event and a downward crossing will generate a DOWN event. The CROSS event will be generated every time there is a crossing, independent of direction.

The immediate value of the comparator can be sampled to RESULT register by triggering the SAMPLE task.

ISOURCE

An optional configurable current can be applied on the AINx pad currently selected for VIN+, as illustrated in the following figure. The AINx pad is configured in register PSEL and the current source in register ISOURCE.

Figure 2. Using the configurable current source

Diagram: Comparator ISOURCE

Enabling ISOURCE creates a feedback path around the comparator, forming a relaxation oscillator. The circuit will sink current from VIN+ when the comparator output is high, and source current into VIN+ when the comparator output is low. The frequency of the oscillator is dependent on the capacitance at the analog input pin, the reference voltages, and the value of the current source. When using ISOURCE, a capacitive sensor can to be attached between the analog input pin and ground. With a selected current of 10 μA, VUP-VDOWN equal to 1 V, and an external capacity of typically 10 pF, the resulting oscillation frequency is around 500 kHz.

The frequency of the oscillator can be calculated using the following equation:
f_OSC = I_SOURCE / (2C∙(VUP-VDOWN) )
Note: The current source can be enabled in any of the comparator modes.

Shared resources

The COMP shares analog resources with other analog peripherals.

While it is possible to use the SAADC at the same time as the COMP, selecting the same analog input pin for both peripherals is not supported.

Additionally, COMP shares registers and other resources with other peripherals that have the same ID as the COMP. See Peripherals with shared ID for more information.

The COMP peripheral shall not be disabled (by writing to the ENABLE register) before the peripheral has been stopped. Failing to do so may result in unpredictable behavior.

Differential mode

In differential mode, the reference input VIN- is derived directly from one of the AINx pins.

Before enabling the comparator via the ENABLE register, the following registers must be configured for the differential mode:

Figure 3. Comparator in differential mode

Comparator in differential mode

Note: Depending on the device, not all the analog inputs may be available for each MUX. See definitions for PSEL and EXTREFSEL for more information about which analog pins are available on a particular device.

When the HYST register is turned on during this mode, the output of the comparator and associated events do the following:

  • Change from ABOVE to BELOW when VIN+ drops below VIN- - (VDIFFHYST/2)
  • Change from BELOW to ABOVE when VIN+ raises above VIN- + (VDIFFHYST/2)

This behavior is illustrated in the following figure.

Figure 4. Hysteresis enabled in differential mode


Single-ended mode

In single-ended mode, VIN- is derived from the reference ladder.

Before enabling the comparator via the ENABLE register, the following registers must be configured for the single-ended mode:

The reference ladder uses the reference voltage (VREF) to derive two new voltage references, VUP and VDOWN. VUP and VDOWN are configured using THUP and THDOWN respectively in the TH register. VREF can be derived from any of the available reference sources, configured using the EXTREFSEL and REFSEL registers as shown in the following figure. When AREF is selected in the REFSEL register, the EXTREFSEL register is used to select one of the AIN0-AIN7 analog input pins as reference input. The selected analog pins will be acquired by the comparator once it is enabled.

Figure 5. Comparator in single-ended mode

Diagram: Comparator in single-ended mode

Note: Depending on the device, not all the analog inputs may be available for each MUX. See definitions for PSEL and EXTREFSEL for more information about which analog pins are available on a particular device.

When the comparator core detects that VIN+ > VIN-, i.e. ABOVE as per the RESULT register, VIN- will switch to VDOWN. When VIN+ falls below VIN- again, VIN- will be switched back to VUP. By specifying VUP larger than VDOWN, a hysteresis can be generated as illustrated in the following figures.

Writing to HYST has no effect in single-ended mode, and the content of this register is ignored.

Figure 6. Hysteresis example where VIN+ starts below VUP

Hysteresis example where VIN+ starts below VUP

Figure 7. Hysteresis example where VIN+ starts above VUP

Hysteresis example where VIN+ starts above VUP

Registers

Instances

InstanceDomainBase addressTrustZoneSplit accessDescription
MapAttDMA

COMP : S
COMP : NS

APPLICATION

0x5001A000
0x4001A000

USSNANo

Comparator

Register overview

RegisterOffsetTZDescription
TASKS_START0x000

Start comparator

TASKS_STOP0x004

Stop comparator

TASKS_SAMPLE0x008

Sample comparator value

SUBSCRIBE_START0x080

Subscribe configuration for task START

SUBSCRIBE_STOP0x084

Subscribe configuration for task STOP

SUBSCRIBE_SAMPLE0x088

Subscribe configuration for task SAMPLE

EVENTS_READY0x100

COMP is ready and output is valid

EVENTS_DOWN0x104

Downward crossing

EVENTS_UP0x108

Upward crossing

EVENTS_CROSS0x10C

Downward or upward crossing

PUBLISH_READY0x180

Publish configuration for event READY

PUBLISH_DOWN0x184

Publish configuration for event DOWN

PUBLISH_UP0x188

Publish configuration for event UP

PUBLISH_CROSS0x18C

Publish configuration for event CROSS

SHORTS0x200

Shortcuts between local events and tasks

INTEN0x300

Enable or disable interrupt

INTENSET0x304

Enable interrupt

INTENCLR0x308

Disable interrupt

RESULT0x400

Compare result

ENABLE0x500

COMP enable

PSEL0x504

Pin select

REFSEL0x508

Reference source select for single-ended mode

EXTREFSEL0x50C

External reference select

TH0x530

Threshold configuration for hysteresis unit

MODE0x534

Mode configuration

HYST0x538

Comparator hysteresis enable

ISOURCE0x53C

Current source select on analog input

TASKS_START

Address offset: 0x000

Start comparator

Bit number313029282726252423222120191817161514131211109876543210
IDA
Reset 0x0000000000000000000000000000000000000000
IDR/WFieldValue IDValueDescription
A

W

TASKS_START

Start comparator

Trigger

1

Trigger task

TASKS_STOP

Address offset: 0x004

Stop comparator

Bit number313029282726252423222120191817161514131211109876543210
IDA
Reset 0x0000000000000000000000000000000000000000
IDR/WFieldValue IDValueDescription
A

W

TASKS_STOP

Stop comparator

Trigger

1

Trigger task

TASKS_SAMPLE

Address offset: 0x008

Sample comparator value

Bit number313029282726252423222120191817161514131211109876543210
IDA
Reset 0x0000000000000000000000000000000000000000
IDR/WFieldValue IDValueDescription
A

W

TASKS_SAMPLE

Sample comparator value

Trigger

1

Trigger task

SUBSCRIBE_START

Address offset: 0x080

Subscribe configuration for task START

Bit number313029282726252423222120191817161514131211109876543210
IDBAAAAAAAA
Reset 0x0000000000000000000000000000000000000000
IDR/WFieldValue IDValueDescription
A

RW

CHIDX

[0..255]

DPPI channel that task START will subscribe to

B

RW

EN

Disabled

0

Disable subscription

Enabled

1

Enable subscription

SUBSCRIBE_STOP

Address offset: 0x084

Subscribe configuration for task STOP

Bit number313029282726252423222120191817161514131211109876543210
IDBAAAAAAAA
Reset 0x0000000000000000000000000000000000000000
IDR/WFieldValue IDValueDescription
A

RW

CHIDX

[0..255]

DPPI channel that task STOP will subscribe to

B

RW

EN

Disabled

0

Disable subscription

Enabled

1

Enable subscription

SUBSCRIBE_SAMPLE

Address offset: 0x088

Subscribe configuration for task SAMPLE

Bit number313029282726252423222120191817161514131211109876543210
IDBAAAAAAAA
Reset 0x0000000000000000000000000000000000000000
IDR/WFieldValue IDValueDescription
A

RW

CHIDX

[0..255]

DPPI channel that task SAMPLE will subscribe to

B

RW

EN

Disabled

0

Disable subscription

Enabled

1

Enable subscription

EVENTS_READY

Address offset: 0x100

COMP is ready and output is valid

Bit number313029282726252423222120191817161514131211109876543210
IDA
Reset 0x0000000000000000000000000000000000000000
IDR/WFieldValue IDValueDescription
A

RW

EVENTS_READY

COMP is ready and output is valid

NotGenerated

0

Event not generated

Generated

1

Event generated

EVENTS_DOWN

Address offset: 0x104

Downward crossing

Bit number313029282726252423222120191817161514131211109876543210
IDA
Reset 0x0000000000000000000000000000000000000000
IDR/WFieldValue IDValueDescription
A

RW

EVENTS_DOWN

Downward crossing

NotGenerated

0

Event not generated

Generated

1

Event generated

EVENTS_UP

Address offset: 0x108

Upward crossing

Bit number313029282726252423222120191817161514131211109876543210
IDA
Reset 0x0000000000000000000000000000000000000000
IDR/WFieldValue IDValueDescription
A

RW

EVENTS_UP

Upward crossing

NotGenerated

0

Event not generated

Generated

1

Event generated

EVENTS_CROSS

Address offset: 0x10C

Downward or upward crossing

Bit number313029282726252423222120191817161514131211109876543210
IDA
Reset 0x0000000000000000000000000000000000000000
IDR/WFieldValue IDValueDescription
A

RW

EVENTS_CROSS

Downward or upward crossing

NotGenerated

0

Event not generated

Generated

1

Event generated

PUBLISH_READY

Address offset: 0x180

Publish configuration for event READY

Bit number313029282726252423222120191817161514131211109876543210
IDBAAAAAAAA
Reset 0x0000000000000000000000000000000000000000
IDR/WFieldValue IDValueDescription
A

RW

CHIDX

[0..255]

DPPI channel that event READY will publish to

B

RW

EN

Disabled

0

Disable publishing

Enabled

1

Enable publishing

PUBLISH_DOWN

Address offset: 0x184

Publish configuration for event DOWN

Bit number313029282726252423222120191817161514131211109876543210
IDBAAAAAAAA
Reset 0x0000000000000000000000000000000000000000
IDR/WFieldValue IDValueDescription
A

RW

CHIDX

[0..255]

DPPI channel that event DOWN will publish to

B

RW

EN

Disabled

0

Disable publishing

Enabled

1

Enable publishing

PUBLISH_UP

Address offset: 0x188

Publish configuration for event UP

Bit number313029282726252423222120191817161514131211109876543210
IDBAAAAAAAA
Reset 0x0000000000000000000000000000000000000000
IDR/WFieldValue IDValueDescription
A

RW

CHIDX

[0..255]

DPPI channel that event UP will publish to

B

RW

EN

Disabled

0

Disable publishing

Enabled

1

Enable publishing

PUBLISH_CROSS

Address offset: 0x18C

Publish configuration for event CROSS

Bit number313029282726252423222120191817161514131211109876543210
IDBAAAAAAAA
Reset 0x0000000000000000000000000000000000000000
IDR/WFieldValue IDValueDescription
A

RW

CHIDX

[0..255]

DPPI channel that event CROSS will publish to

B

RW

EN

Disabled

0

Disable publishing

Enabled

1

Enable publishing

SHORTS

Address offset: 0x200

Shortcuts between local events and tasks

Bit number313029282726252423222120191817161514131211109876543210
IDEDCBA
Reset 0x0000000000000000000000000000000000000000
IDR/WFieldValue IDValueDescription
A

RW

READY_SAMPLE

Shortcut between event READY and task SAMPLE

Disabled

0

Disable shortcut

Enabled

1

Enable shortcut

B

RW

READY_STOP

Shortcut between event READY and task STOP

Disabled

0

Disable shortcut

Enabled

1

Enable shortcut

C

RW

DOWN_STOP

Shortcut between event DOWN and task STOP

Disabled

0

Disable shortcut

Enabled

1

Enable shortcut

D

RW

UP_STOP

Shortcut between event UP and task STOP

Disabled

0

Disable shortcut

Enabled

1

Enable shortcut

E

RW

CROSS_STOP

Shortcut between event CROSS and task STOP

Disabled

0

Disable shortcut

Enabled

1

Enable shortcut

INTEN

Address offset: 0x300

Enable or disable interrupt

Bit number313029282726252423222120191817161514131211109876543210
IDDCBA
Reset 0x0000000000000000000000000000000000000000
IDR/WFieldValue IDValueDescription
A

RW

READY

Enable or disable interrupt for event READY

Disabled

0

Disable

Enabled

1

Enable

B

RW

DOWN

Enable or disable interrupt for event DOWN

Disabled

0

Disable

Enabled

1

Enable

C

RW

UP

Enable or disable interrupt for event UP

Disabled

0

Disable

Enabled

1

Enable

D

RW

CROSS

Enable or disable interrupt for event CROSS

Disabled

0

Disable

Enabled

1

Enable

INTENSET

Address offset: 0x304

Enable interrupt

Bit number313029282726252423222120191817161514131211109876543210
IDDCBA
Reset 0x0000000000000000000000000000000000000000
IDR/WFieldValue IDValueDescription
A

RW

READY

Write '1' to enable interrupt for event READY

Set

1

Enable

Disabled

0

Read: Disabled

Enabled

1

Read: Enabled

B

RW

DOWN

Write '1' to enable interrupt for event DOWN

Set

1

Enable

Disabled

0

Read: Disabled

Enabled

1

Read: Enabled

C

RW

UP

Write '1' to enable interrupt for event UP

Set

1

Enable

Disabled

0

Read: Disabled

Enabled

1

Read: Enabled

D

RW

CROSS

Write '1' to enable interrupt for event CROSS

Set

1

Enable

Disabled

0

Read: Disabled

Enabled

1

Read: Enabled

INTENCLR

Address offset: 0x308

Disable interrupt

Bit number313029282726252423222120191817161514131211109876543210
IDDCBA
Reset 0x0000000000000000000000000000000000000000
IDR/WFieldValue IDValueDescription
A

RW

READY

Write '1' to disable interrupt for event READY

Clear

1

Disable

Disabled

0

Read: Disabled

Enabled

1

Read: Enabled

B

RW

DOWN

Write '1' to disable interrupt for event DOWN

Clear

1

Disable

Disabled

0

Read: Disabled

Enabled

1

Read: Enabled

C

RW

UP

Write '1' to disable interrupt for event UP

Clear

1

Disable

Disabled

0

Read: Disabled

Enabled

1

Read: Enabled

D

RW

CROSS

Write '1' to disable interrupt for event CROSS

Clear

1

Disable

Disabled

0

Read: Disabled

Enabled

1

Read: Enabled

RESULT

Address offset: 0x400

Compare result

Bit number313029282726252423222120191817161514131211109876543210
IDA
Reset 0x0000000000000000000000000000000000000000
IDR/WFieldValue IDValueDescription
A

R

RESULT

Result of last compare. Decision point SAMPLE task.

Below

0

Input voltage is below the threshold (VIN+ < VIN-)

Above

1

Input voltage is above the threshold (VIN+ > VIN-)

ENABLE

Address offset: 0x500

COMP enable

Bit number313029282726252423222120191817161514131211109876543210
IDAA
Reset 0x0000000000000000000000000000000000000000
IDR/WFieldValue IDValueDescription
A

RW

ENABLE

Enable or disable COMP

Disabled

0

Disable

Enabled

2

Enable

PSEL

Address offset: 0x504

Pin select

Bit number313029282726252423222120191817161514131211109876543210
IDAAA
Reset 0x0000000000000000000000000000000000000000
IDR/WFieldValue IDValueDescription
A

RW

PSEL

Analog pin select

AnalogInput0

0

AIN0 selected as analog input

AnalogInput1

1

AIN1 selected as analog input

AnalogInput2

2

AIN2 selected as analog input

AnalogInput3

3

AIN3 selected as analog input

AnalogInput4

4

AIN4 selected as analog input

AnalogInput5

5

AIN5 selected as analog input

AnalogInput6

6

AIN6 selected as analog input

AnalogInput7

7

AIN7 selected as analog input

REFSEL

Address offset: 0x508

Reference source select for single-ended mode

Bit number313029282726252423222120191817161514131211109876543210
IDAAA
Reset 0x0000000400000000000000000000000000000100
IDR/WFieldValue IDValueDescription
A

RW

REFSEL

Reference select

Int1V2

0

VREF = internal 1.2 V reference (VDD >= 1.7 V)

Int1V8

1

VREF = internal 1.8 V reference (VDD >= VREF + 0.2 V)

Int2V4

2

VREF = internal 2.4 V reference (VDD >= VREF + 0.2 V)

VDD

4

VREF = VDD

ARef

5

VREF = AREF

EXTREFSEL

Address offset: 0x50C

External reference select

Bit number313029282726252423222120191817161514131211109876543210
IDAAA
Reset 0x0000000000000000000000000000000000000000
IDR/WFieldValue IDValueDescription
A

RW

EXTREFSEL

External analog reference select

AnalogReference0

0

Use AIN0 as external analog reference

AnalogReference1

1

Use AIN1 as external analog reference

AnalogReference2

2

Use AIN2 as external analog reference

AnalogReference3

3

Use AIN3 as external analog reference

AnalogReference4

4

Use AIN4 as external analog reference

AnalogReference5

5

Use AIN5 as external analog reference

AnalogReference6

6

Use AIN6 as external analog reference

AnalogReference7

7

Use AIN7 as external analog reference

TH

Address offset: 0x530

Threshold configuration for hysteresis unit

Bit number313029282726252423222120191817161514131211109876543210
IDBBBBBBAAAAAA
Reset 0x0000000000000000000000000000000000000000
IDR/WFieldValue IDValueDescription
A

RW

THDOWN

[63:0]

VDOWN = (THDOWN+1)/64*VREF

B

RW

THUP

[63:0]

VUP = (THUP+1)/64*VREF

MODE

Address offset: 0x534

Mode configuration

Bit number313029282726252423222120191817161514131211109876543210
IDBAA
Reset 0x0000000000000000000000000000000000000000
IDR/WFieldValue IDValueDescription
A

RW

SP

Speed and power modes

Low

0

Low-power mode

Normal

1

Normal mode

High

2

High-speed mode

B

RW

MAIN

Main operation modes

SE

0

Single-ended mode

Diff

1

Differential mode

HYST

Address offset: 0x538

Comparator hysteresis enable

Bit number313029282726252423222120191817161514131211109876543210
IDA
Reset 0x0000000000000000000000000000000000000000
IDR/WFieldValue IDValueDescription
A

RW

HYST

Comparator hysteresis

NoHyst

0

Comparator hysteresis disabled

Hyst50mV

1

Comparator hysteresis enabled

ISOURCE

Address offset: 0x53C

Current source select on analog input

Bit number313029282726252423222120191817161514131211109876543210
IDAA
Reset 0x0000000000000000000000000000000000000000
IDR/WFieldValue IDValueDescription
A

RW

ISOURCE

Comparator hysteresis

Off

0

Current source disabled

Ien2mA5

1

Current source enabled (+/- 2.5 uA)

Ien5mA

2

Current source enabled (+/- 5 uA)

Ien10mA

3

Current source enabled (+/- 10 uA)

Electrical specification

COMP Electrical Specification

SymbolDescriptionMin.Typ.Max.Units
tPROPDLY,LP

Propagation delay, Low-power mode1

0.6µs
tPROPDLY,N

Propagation delay, Normal mode1

0.2µs
tPROPDLY,HS

Propagation delay, High-speed mode1

0.1µs
VDIFFHYST

Optional hysteresis applied to differential input

263555mV
VVDD-VREF

Required difference between VDD and a selected VREF, VDD > VREF

0.3V
tINT_REF,START

Startup time for the internal bandgap reference

5080µs
EINT_REF

Internal bandgap reference error

-1.800.5%
VINPUTOFFSET

Input offset

-1010mV
tCOMP,START

Startup time for the comparator core

3µs

COMP Current Source (ISOURCE) Specification

Configurable current provided by the current source, excluding variations over temperature and voltage, at 3 V and 25°C. For other voltages and temperatures, the accuracy as specified by ISOURCE,ACC must be added to the min and max values.

SymbolDescriptionMin.Typ.Max.Units
ISOURCE,A

Current when register ISOURCE=Ien2mA5

1.62.43.3µA
ISOURCE,B

Current when register ISOURCE=Ien5mA

3.24.96.5µA
ISOURCE,C

Current when register ISOURCE=Ien10mA

6.09.813.0µA
ISOURCE,ACC

Current source accuracy over temperature and voltage

±5%%
1 Propagation delay is with 10 mV overdrive.