DIODES ZXCT1086 Current Monitors User Guide

DIODES ZXCT1086 Current Monitors

Introduction

This evaluation circuit simply demonstrates the ZXCT1086 60V High-Side Current Monitor with a fixed gain of 50. 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 2.5V or 5.0V 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).

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 50
• Accuracy 2%
• Ambient temperature range -40 to 105°C

Ordering Information

• Order Number: ZXCT1086EV1

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| ZXCT1086| SOT23-5| Diodes| ZXCT1086E5TA

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 50 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 2.5V at the Output per Ampere of current in the sense resistor. The second sense resistor provided is 100 milliohms, providing a sensitivity of 5.0V 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 = 50
• The sensitivity to current is VOUT/ILOAD = (VOUT/VSENSE) . (VSENSE/ILOAD) = 50 . R1 = 2.5 V per Amp.
• If SL2 is bridged instead of SL1, the sense resistance will be 0.1R, so the sensitivity will then be 5.0 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 2.5V due to the PCB copper resistance, including the solder link, when using the 50 million hm sense resistor, R1.
2. The tolerance of the sense resistor R1 is ±1%.
3. The ZXCT1086 tolerance is ±1%.
4. The Fluke DMM has an input resistance of about 11Mohm, while the ZXCT1086EV1 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 ZXCT1086EV1 board, solder link SL1 is bridged and SL2 is open.
3. Connect up the ZXCT1086EV1 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 2.47V and 2.58V. [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

5%, 10W, or electronic load, 60V 2A

| |

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