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
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

Diagram: Comparator overview — Figure 1. 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 t_{INT_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 V_DIFFHYST, 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.

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 2. 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- - (V_DIFFHYST/2)
Change from BELOW to ABOVE when VIN+ raises above VIN- + (V_DIFFHYST/2)

This behavior is illustrated in the following figure.

Figure 3. 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.

Diagram: Comparator in single-ended mode — Figure 4. Comparator in single-ended mode

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 5. Hysteresis example where VIN+ starts below VUP

Figure 6. Hysteresis example where VIN+ starts above VUP

Registers

Instances


Instance	Base address	Description
COMP	0x40013000	General purpose comparator

Register overview


Register	Offset	Description
TASKS_START	0x000	Start comparator
TASKS_STOP	0x004	Stop comparator
TASKS_SAMPLE	0x008	Sample comparator value
EVENTS_READY	0x100	COMP is ready and output is valid
EVENTS_DOWN	0x104	Downward crossing
EVENTS_UP	0x108	Upward crossing
EVENTS_CROSS	0x10C	Downward or upward crossing
SHORTS	0x200	Shortcuts between local events and tasks
INTEN	0x300	Enable or disable interrupt
INTENSET	0x304	Enable interrupt
INTENCLR	0x308	Disable interrupt
RESULT	0x400	Compare result
ENABLE	0x500	COMP enable
PSEL	0x504	Pin select
REFSEL	0x508	Reference source select for single-ended mode
EXTREFSEL	0x50C	External reference select
TH	0x530	Threshold configuration for hysteresis unit
MODE	0x534	Mode configuration
HYST	0x538	Comparator hysteresis enable

TASKS_START

Address offset: 0x000

Start comparator


Bit number				31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
ID																																			A
Reset 0x00000000				0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value								Description
A	W	TASKS_START										Start comparator
			Trigger	1								Trigger task

TASKS_STOP

Address offset: 0x004

Stop comparator


Bit number				31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
ID																																			A
Reset 0x00000000				0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value								Description
A	W	TASKS_STOP										Stop comparator
			Trigger	1								Trigger task

TASKS_SAMPLE

Address offset: 0x008

Sample comparator value


Bit number				31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
ID																																			A
Reset 0x00000000				0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value								Description
A	W	TASKS_SAMPLE										Sample comparator value
			Trigger	1								Trigger task

EVENTS_READY

Address offset: 0x100

COMP is ready and output is valid


Bit number				31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
ID																																			A
Reset 0x00000000				0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value								Description
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 number				31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
ID																																			A
Reset 0x00000000				0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value								Description
A	RW	EVENTS_DOWN										Downward crossing
			NotGenerated	0								Event not generated
			Generated	1								Event generated

EVENTS_UP

Address offset: 0x108

Upward crossing


Bit number				31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
ID																																			A
Reset 0x00000000				0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value								Description
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 number				31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
ID																																			A
Reset 0x00000000				0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value								Description
A	RW	EVENTS_CROSS										Downward or upward crossing
			NotGenerated	0								Event not generated
			Generated	1								Event generated

SHORTS

Address offset: 0x200

Shortcuts between local events and tasks


Bit number				31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
ID																															E	D	C	B	A
Reset 0x00000000				0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value								Description
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 number				31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
ID																																D	C	B	A
Reset 0x00000000				0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value								Description
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 number				31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
ID																																D	C	B	A
Reset 0x00000000				0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value								Description
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 number				31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
ID																																D	C	B	A
Reset 0x00000000				0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value								Description
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 number				31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
ID																																			A
Reset 0x00000000				0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value								Description
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 number				31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
ID																																		A	A
Reset 0x00000000				0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value								Description
A	RW	ENABLE										Enable or disable COMP
			Disabled	0								Disable
			Enabled	2								Enable

PSEL

Address offset: 0x504

Pin select


Bit number				31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
ID																																	A	A	A
Reset 0x00000000				0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value								Description
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 number				31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
ID																																	A	A	A
Reset 0x00000004				0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	1	0	0
ID	R/W	Field	Value ID	Value								Description
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 number				31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
ID																																	A	A	A
Reset 0x00000000				0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value								Description
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 number				31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
ID																						B	B	B	B	B	B			A	A	A	A	A	A
Reset 0x00000000				0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value								Description
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 number				31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
ID																											B							A	A
Reset 0x00000000				0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value								Description
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 number				31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
ID																																			A
Reset 0x00000000				0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value								Description
A	RW	HYST										Comparator hysteresis
			NoHyst	0								Comparator hysteresis disabled
			Hyst50mV	1								Comparator hysteresis enabled

Electrical specification

COMP Electrical Specification


Symbol	Description	Min.	Typ.	Max.	Units
t_PROPDLY,LP	Propagation delay, Low-power mode^¹		0.6		µs
t_PROPDLY,N	Propagation delay, Normal mode^¹		0.2		µs
t_PROPDLY,HS	Propagation delay, High-speed mode^¹		0.1		µs
V_DIFFHYST	Optional hysteresis applied to differential input	10	30	90	mV
V_VDD-VREF	Required difference between VDD and a selected VREF, VDD > VREF	0.3			V
t_{INT_REF,START}	Startup time for the internal bandgap reference		50	80	µs
E_{INT_REF}	Internal bandgap reference error	-3		3	%
V_INPUTOFFSET	Input offset	-15		15	mV
t_COMP,START	Startup time for the comparator core		3		µs

¹ Propagation delay is with 10 mV overdrive.