DIODES ZXCT1084EV1 Current Monitoring User Guide

DIODES ZXCT1084EV1 Current Monitoring

Product Information

Specifications

• Order Number: ZXCT1084EV1
• Input Voltage: 2.7V – 60V
• Supply Voltage : 2.7V – 60V
• Output Voltage: 0V to Load Voltage – 1V
• Operating Ambient Temperature: -40°C to 105°C

Performance

• Current Monitor with wide supply range: 2.7V to 60V
• Independent chip supply and supply-tobe- monitored
• Low quiescent current (25μA typ)
• Fixed gain of 25
• Accuracy 2%
• Ambient temperature range
  • 40 to 105°C

Introduction
This evaluation circuit simply demonstrates the ZXCT1084 60V High-Side Current Monitor with a fixed gain of 25. The circuit is suitable for a wide range of power systems including automotive and industrial applications as well as portable and battery management systems. The sensitivity of the PCB can be selected using solder bridge links to either 1.25V or 2.5V per Ampere of load current. The construction is a double-sided FR4 printed circuit board, 51 x 64 x 1.6 mm with 2oz/sq ft copper (70μm).

Ordering Information

• Order Number: ZXCT1084EV1

Schematic

PCB Layout

Parts List

Count| Designator| Description| Package| Manufacturer| Part Number
---|---|---|---|---|---
1| C1| Capacitor SMD, 100nF 100V X7R| 0805| AVX| 08051C104KAZ2A
0| C2| NOT FTTED|  |  |

1

|

R1

| Resistor, SMD, 0R05 1% 500mW

100ppm/ °C

|

1206

|

Welwyn

|

LR1206-R05FI

1

|

R2

| Resistor, SMD, 0R1 1% 500mW

100ppm/ °C

|

1206

|

Welwyn

|

LR1206-R10FI

1| R3| NOT FITTED|  |  |
2| R4, R5| Resistor, SMD, 0R

125mW

| 0805| various|
1| R6| NOT FITTED|  |  |
1| U1| ZXCT1084| SOT23-5| Diodes| ZXCT1084E5TA

PCB Sensitivity Selection
The sensitivity of the PCB can be adjusted by solder bridge links to achieve either 1.25V or 2.5V per Ampere of load current.

Product Usage Instructions

I/O and Test points

Count| Designator| Description| Function| Manufacturer| Part Number
---|---|---|---|---|---
1| TP1| Loop Terminal, 2.15mm, green| Input| Hughes| 100-108
1| TP2| Loop Terminal, 2.15mm, green| Vcc| Hughes| 100-108
1| TP3| Loop Terminal, 2.15mm, green| Ground| Hughes| 100-108
1| TP4| Loop Terminal, 2.15mm, green| Load| Hughes| 100-108
1| TP5| Loop Terminal, 2.15mm, green| Ground| Hughes| 100-108
1| TP6| Loop Terminal, 2.15mm, green| Output| Hughes| 100-108
1| TP7| Loop Terminal, 2.15mm, green| Ground| Hughes| 100-108
1| TP8| Loop Terminal, 2.15mm, green| Ground| Hughes| 100-108

Recommended Operating Conditions

-1V

| V
TA| Operating Ambient Temperature| -40| 105| °C

Detailed Description
The voltage gain from the sense inputs is set to 25 internally to the chip. Two current sense resistors are provided, which can be selected by solder bridge links. In the initial factory setting, SL1 is connected and SL2 is not, so the sense resistor value is R1=50 milliohms, giving a sensitivity of 1.25V at the Output per Ampere of current in the sense resistor. The second sense resistor provided is 100 milliohms, providing a sensitivity of 2.5V per Ampere. Through-holes are provided for the user to fit an additional resistor R3 if desired.

If SL1 only is bridged, the sensitivity of the PCB assembly to load current is set by R1 which is a 1% tolerance thick film resistor of 50 milliohms.

• The sense voltage is
  VSENSE = VS+ – VS- = ILOAD . R1, i.e. 50mV per Amp

• The voltage gain is
  VOUT/VSENSE = 25.0

• The sensitivity to current is
  VOUT/ILOAD = (VOUT/VSENSE) . (VSENSE/ILOAD) = 25 . R1 = 1.25 V per Amp.

If SL2 is bridged instead of SL1, the sense resistance will be 0.1R, so the sensitivity will then be 2.5 V per Amp.

A Note on Tolerance
The output voltage tolerance as measured in the Quick Start Guide, below, is approximately +3%, -1%. This consists of the following contributions:

1. The reading is about 2% higher than the nominal value of 1.25V due to the PCB copper resistance, including the solder link, when using the 50 milliohm sense resistor, R1.
2. The tolerance of the sense resistor R1 is ±1%.
3. The ZXCT1084 tolerance is ±1%.
4. The Fluke DMM has an input resistance of about 11Mohm, while the ZXCT1084EV1 output resistance is 125kohm. This means that the reading will be about 1.1% lower than a perfect voltmeter.

Quick Start Guide
Suitable test equipment is given in the table below.

1. Set the power supply to 10.0V but do not switch on. Set the current limit to 1.5A.
2. Check that on the ZXCT1084EV1 board, solder link SL1 is bridged and SL2 is open.
3. Connect up the ZXCT1084EV1 board to the equipment as in the diagram below. Set DMM1 to measure voltage and DMM2 to measure current.
4. Switch on the power supply. DMM2 should now read about 1.0A. Adjust the supply voltage slightly to obtain exactly 1.000A ± 0.005A.
5. DMM1 now reads between 1.23V and 1.29V. [This tolerance band includes the effects listed above.]
6. You can examine operation at 60V easily if the electronic load is available. Set the load to 1.00A and increase the power supply voltage to 60V.

Suitable Test Equipment

1

| Load resistor, 10 ohms ± 5%, 10W, or electronic load, 60V 2A|  |

Detailed Description of Sensitivity Selection
If SL1 is bridged, the sensitivity is set by R1, a 50 milliohm resistor, resulting in a sensitivity of 1.25V per Amp. If SL2 is bridged instead, the sensitivity will be 2.5V per Amp.

Note on Tolerance
The output voltage tolerance is approximately +3%, -1% due to factors like PCB copper resistance and DMM input resistance compared to the ZXCT1084EV1 output resistance.

IMPORTANT NOTICE
DIODES INCORPORATED MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARD TO THIS DOCUMENT, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE (AND THEIR EQUIVALENTS UNDER THE LAWS OF ANY JURISDICTION).

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As used herein:

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Copyright © 2009, Diodes Incorporated
www.diodes.com

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Issue 1 – October 2009
© Diodes Incorporated 2009
www.diodes.com

FAQ

What is the purpose of solder bridge links on the PCB?
The solder bridge links are used to select the sensitivity of the PCB to load current, allowing for adjustments between 1.25V and 2.5V per Ampere.

How can I adjust the sensitivity of the ZXCT1084EV1 evaluation circuit?
To adjust sensitivity, bridge either SL1 or SL2 on the board based on the desired sensitivity level of 1.25V or 2.5V per Ampere, respectively.

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