Rev. 0.1 8/15 Copyright © 2015 by Silicon Laboratories Si8920ISO-EVB
Si8920ISO-EVB
Si8920ISO-EVB USER’S GUIDE
Description
This document describes the operation of the
Si8920ISO-EVB.
Kit Contents
The Si8920ISO Evaluation Kit contains the following
items:
Si8920ISO-EVB.
Si8920BC-IP installed on the evaluation board.
Si8920ISO-EVB Overview
Si8920ISO-EVB
2 Rev. 0.1
1. Hardware Overview and Setup
1.1. Connecting to the EVB
Power the EVB by applying isolated 3.0 to 5.5 VDC supplies to terminal blocks J1 and J2. LEDs D21 and D22 will
light up. Use separate test points TP1, TP2, TP3, and TP4 for observing VDDA, GNDA, VDDB, and GNDB,
respectively.
Note: DO NOT place jumpers across JP10, JP11, or JP12. These are redundant test points for VDDA, VDDB, and AOP/AON,
respectively.
There are three connection points for applying and observing differential signals to the inputs of Si8920:
1. Through a two conductor ribbon cable to 2x1 header JP8.
2. Clipping wires to test points TP7 and TP8.
3. Soldering wires directly to through holes located at TP9 and TP10.
The same connector options are available for observing and taking the output signals off circuit board:
1. Through a two conductor ribbon cable at 2x1 header JP12.
2. Clipping wires to test points TP5 and TP6.
3. Soldering wires directly through holes located at TP11 and TP12.
1.2. Driving Si8920 Inputs
Drive the inputs with a low impedance source. The Si8920 has a typical input impedance of 37.2 kΩ. A high source
impedance will affect the gain error of the amplifier. The maximum specified differential voltage is 200 mV and the
common mode must be within –250 mV to 1 V with respect to GNDA.
Note: When driving inputs from a single-ended source, short the unused input to GNDA. If driving AIP input, install 0 Ω resistor
across C23 pads. If driving AIN input, install a 0 Ω resistor across C24 pads.
Si8920ISO-EVB
Rev. 0.1 3
1.3. Input Configuration
To measure input offset, install a jumper (not provided) at JP8 to short AIP and AIN together, and measure the
difference voltage between AOP and AON.
Si8920 has a channel bandwidth of approximately 750 kHz. R9-C7-R10 are populated providing low pass filtering
with cutoff frequency of approximately 400 kHz. If a different cutoff frequency is desired, replace C7 per Table 1. If
it is necessary to replace R9 and R10 for a specific cutoff frequency, ensure that R9 = R10 < 33 Ω.
Si8920 has excellent immunity to common mode transients. This EVB provides provisions for capacitors C23 and
C24 (not populated) between each input pin and GNDA. Placing a small capacitor at C23 and C24 can assist with
charge swapping between the inputs and GNDA during common mode transients. However, any mismatch
between C23 and C24 will result as a gain error at the output.
1.4. Observing Si8920 Outputs
Use a differential probe when observing the output using an oscilloscope. Most differential oscilloscope probes will
connect to the 2x1 headers JP12 without adapters. If only single-ended oscilloscope probes are available, use two
and set oscilloscope to subtract the two channels as one channel will only show half of the output.
Table 1. Input Filter Cutoff Frequency for Common Capacitor Values with R9 = R10 = 20 Ω
C7 (nF) Cutoff Frequency (kHz)
10* 398
15 265
22 181
33 121
47 85
*Note: Installed value.
Si8920ISO-EVB
4 Rev. 0.1
1.5. Output Configuration
By default, R23 and R24 are populated with 0 Ω resistors that pass the output signal to the output connectors. If
low pass filtering at the output is required, replace R23 and R24 and populate C22.
R25 can be populated to measure the differential output drive strength. R26 and R27 can be populated to measure
the common mode drive strength to GNDB.
Table 2. Test Point Descriptions
Test Point Description Reference
TP1 VDDA GNDA
TP2 GNDA N/A
TP3 VDDB GNDB
TP4 GNDB N/A
TP5 AOP GNDB
TP6 AON GNDB
TP7 AIP GNDA
TP8 AIN GNDA
TP13 GNDA N/A
TP14 GNDB N/A
Table 3. Jumper Descriptions
Jumper PIN 1 PIN 2 Default Position Description
JP8 AIN AIP Not Installed Analog Input Connector, Short to Measure Offset
JP10 VDDA GNDA Not Installed DO NOT SHORT – test points only
JP11 VDDB GNDB Not Installed DO NOT SHORT – test points only
JP12 AON AOP Not Installed DO NOT SHORT – test points only
Si8920ISO-EVB
Rev. 0.1 5
2. Si8920ISO-EVB Schematics
VDDA
TP2
GNDA
TP1
VDDA
VDDA
TP4
GNDB
TP3
VDDB
VDDB
JP8
JP10 JP 11
Output Side Power Supply
Valid range: 3.3V to 5V +/-10%
TP5
AO P
TP6
AO N
Input Connectors
TP7
AIP
TP8
AIN
TP9
NI
TP10
NI
TP11
NI
TP12
NI
JP12
Output Connectors
Do No t
Short
Do No t
Short
Do No t
Short
D21
RED
Input Side Power Supply
J1
1
2
Valid range: 3.3V to 5V +/-10%
R22
10K
D22
RED
J2
1
2
R21
10K
D20
5.6V
TP13
GNDA
TP14
GNDB
VDDB
H1
Si8920
VDD A
GNDA GNDB
VDDB
AIP
AO N
AO P
AIN
D23
5.6V
Figure 1. Si8920ISO-EVB Schematic (1 of 2)
Si8920ISO-EVB
6 Rev. 0.1
U1
VDDA
1
AIP
2
AIN
3
GNDA
4GNDB5
AON6
AOP7
VDDB8R23
0
R24
0
R25
NI
C22
NI
C23
NI
C24
NI
Low Pass Filter
Cutoffat 400kHz
Optional
Output Filter
R26
NI
R27
NI
VDDA
GNDA
C5
0.1uF
C4
10uF
R9
20.0
R10
20.0
C7
0.01uF
C12
0.1uF
C10
10uF
GNDB
VDDB
AIP
AON
AOP
AIN
Figure 2. Si8920ISO-EVB Schematic (2 of 2)
Si8920ISO-EVB
Rev. 0.1 7
3. Si8920ISO-EVB Layout
Figure 3. Si8920ISO-EVB Layout
Top Bottom
Top Silkscreen Bottom Silkscreen
Si8920ISO-EVB
8 Rev. 0.1
4. Bill of Materials
Table 4. Si8920ISO-EVB Bill of Materials
Part Reference Description Manufacturer Manufacturer Part Number
C4, C10 CAP, 10 µF, 10 V, ±20%, X7R, 1206 Venkel C1206X7R100-106M
C5, C12 CAP, 0.1 µF, 10 V, ±10%, X7R, 0603 Venkel C0603X7R100-104K
C7 CAP, 0.01 µF, 16 V, ±10%, X7R, 0603 Venkel C0603X7R160-103K
D20, D23 DIO, ZENER, 28 V, 500 mW, SOD123 On Semi MMSZ5255BT1G
D21, D22 LED, RED, 631 nM, 20 mA, 2 V, 54mcd, 0603 Lite-On LTST-C190KRKT
J1, J2 CONN, TERM BLOCK 2POS, 5MM PCB Phoenix Contact 1729018
JP8, JP10, JP11,
JP12
Header, 2x1, 0.1" pitch, Tin Plated Samtec TSW-102-07-T-S
MH1, MH2, MH3,
MH4
HDW, Screw, 4-40 x 1/4" Pan Head,
Slotted, Nylon
Richco Plastic Co NSS-4-4-01
R9, R10 RES, 20.0 , 1/10 W, ±1%, ThickFilm, 0603 Venkel CR0603-10W-20R0F
R21, R22 RES, 10 K, 1/10 W, ±5%, ThickFilm, 0603 Venkel CR0603-10W-103J
R23, R24 RES, 0 , 1A, ThickFilm, 0603 Venkel CR0603-16W-000
SO1, SO2, SO3,
SO4
HDW, STANDOFF, 1/4" HEX, 4-40x3/4", NYLON Keystone 1902D
TP1, TP2, TP3,
TP4, TP5, TP6,
TP7, TP8
TESTPOINT, BLACK, PTH Kobiconn 151-203-RC
U1 IC, ISOLATED AMPLIFIER FOR CURRENT
SHUNT MEASUREMENT, 8PIN SMD GULL
WING
Silicon Labs Si8920BC-IP
Si8920ISO-EVB
Rev. 0.1 9
5. Ordering Guide
Table 5. Si8920ISO-EVB Ordering Guide
Ordering Part Number (OPN) Description
Si8920ISO-KIT Si8920 Analog isolator evaluation board kit
Si8920ISO-EVB
10 Rev. 0.1
CONTACT INFORMATION
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Austin, TX 78701
Tel: 1+(512) 416-8500
Fax: 1+(512) 416-9669
Toll Free: 1+(877) 444-3032
Please visit the Silicon Labs Technical Support web page:
https://www.siliconlabs.com/support/pages/contacttechnicalsupport.aspx
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