Microchip Technology MA160014 Data Sheet

 2010-2012 Microchip Technology Inc.

DS41412F-page 321

The Charge Time Measurement Unit (CTMU) is a
flexible analog module that provides accurate
differential time measurement between pulse sources,
as well as asynchronous pulse generation. By working
with other on-chip analog modules, the CTMU can be
used to precisely measure time, measure capacitance,
measure relative changes in capacitance or generate
output pulses with a specific time delay. The CTMU is
ideal for interfacing with capacitive-based sensors.

The module includes the following key features:

• Up to 28

(1)

 channels available for capacitive or 

time measurement input

• On-chip precision current source

• Four-edge input trigger sources

• Polarity control for each edge source

• Control of edge sequence

• Control of response to edges

• High precision time measurement

• Time delay of external or internal signal 

asynchronous to system clock

• Accurate current source suitable for capacitive 

measurement

The CTMU works in conjunction with the A/D Converter
to provide up to 28

(1)

 channels for time or charge

measurement, depending on the specific device and
the number of A/D channels available. When config-
ured for time delay, the CTMU is connected to the
C12IN1- input of Comparator 2. The level-sensitive
input edge sources can be selected from four sources:
two external input pins (CTED1/CTED2) or the ECCP1/
(E)CCP2 Special Event Triggers.

 provides a block diagram of the CTMU.

Note 1: PIC18(L)F2XK22 devices have up to 17

channels available.

CTED1

CTED2

Current Source

Edge

Control

Logic

CTMUCONH/CTMUCONL

Pulse

Generator

ECCP2

ECCP1

Current

Control

ITRIM<5:0>
IRNG<1:0>

CTMUICON

CTMU

Control

Logic

EDGEN
EDGSEQEN
EDG1SELx
EDG1POL
EDG2SELx
EDG2POL

EDG1STAT
EDG2STAT

TGEN
IDISSEN

CTPLS

Comparator 2 Output

CTTRIG

Comparator C1/C2 Input

A/D Converter