XtremeSense™ High-Linearity, High-Resolution TMR Current Sensor

with FLAG Output in Miniature Form Factor

CT110

13

Allegro MicroSystems

955 Perimeter Road

Manchester, NH 03103-3353 U.S.A.

www.allegromicro.com

FUNCTIONAL DESCRIPTION

Overview

The CT110 is a high resolution and low noise contact current

sensor with isolation and a FLAG output that operates from 2.7

to 5.5 V assembled in a custom DFN package. The chip mea-

sures the magnetic field of the current through the package and

converts it to an analog signal that is equivalent to the current

flowing through the printed circuit board (PCB) trace. The FLAG

output indicates whether there is an overcurrent condition seen by

CT110 during operation and will alert the host system.

Analog Output Measurement

The CT110 provides a continuous (sample and hold) linear

analog output voltage which represents the measured magnetic

field of the current. The output voltage range of ANA is 5.0%

of VDD to 95.0% of VDD which represents the current from the

typical low-end values (–5.0 A to –15.0 APK) to the maximum

current values (+5.0 A to +15.0 APK) respectively. The output

sample frequency is 200 kHz. A resistor-capacitor (R-C) filter

may be implemented on the ANA pin to further lower the noise.

Figure 17 illustrates the output voltage range of the ANA pin as a

function of the measured current for ±5.0 A.

Current Detection Flag

The Current Detection circuitry detects when the current mea-

sured through the current carrying conductor is above 90% or

below 10% of the full current range. As a result, it translates to

greater than 90% of VDD and 10% of VDD on the ANA pin. This

will generate a flag signal via the FLAG pin to the host system

microcontroller as an active LOW signal. Once VANA falls below

86% or rises above 14% of VDD, then the FLAG signal will go

HIGH.

Rise Time (tRISE)

The CT110 rise time, tRISE, is the time interval of when it reaches

10% and 90% of the full-scale output voltage. The tRISE of the

CT110 is 15.5 µs.

Propagation Delay (tDELAY)

The propagation delay, tDELAY, is the time measured between

ICCC reaching 20% of its final value and the CT110 attaining 20%

of its full-scale output voltage. Its propagation delay is 4.6 µs.

Figure 17: Linear Output Voltage Range vs. Measured

Current for G = –88.2 mV/V/A and current range of ±5.0 A.

Figure 18: CT110 Propagation Delay and Rise Time

Curve

VANA

ICCC

5% VDD

95% VDD

-5.0 A

+5.0 A

50% VDD

0 A

t

VANA

90%

ICCC

tRISE

10%

20%

tDELAY