NRF52811-QCAA-R datasheet(100/444 Pages) NORDIC

100 / 444 page

Peripherals

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

single-ended mode:

• PSEL

• MODE

• REFSEL

• EXTREFSEL

• TH

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 illustrated in Comparator in single-ended mode on page 100. 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.

MUX

REFSEL

VDD

1V2

1V8

2V4

VREF

Comparator

core

MODE

Reference

ladder

VIN-

MUX

VIN+

PSEL

EXTREFSEL

RESULT

MUX

VUP

VDOWN

HYST

Output

0 = BELOW (VIN+ < VIN-)

1 = ABOVE (VIN+ > VIN-)

MUX

AREF

Figure 36: Comparator in single-ended mode

Restriction: 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 Hysteresis example where VIN+ starts below

VUP on page 101 and Hysteresis example where VIN+ starts above VUP on page 101.

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

4454_140 v1.0

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