廬
APPLICATION BULLETIN
By Rod Burt and R. Mark Stitt (602) 746-7445
Mailing Address: PO Box 11400 鈥?Tucson, AZ 85734 鈥?Street Address: 6730 S. Tucson Blvd. 鈥?Tucson, AZ 85706
Tel: (520) 746-1111 鈥?Twx: 910-952-111 鈥?Telex: 066-6491 鈥?FAX (520) 889-1510 鈥?Immediate Product Info: (800) 548-6132
SYNCHRONIZATION OF ISO120/121 ISOLATION AMPLIFIERS
Internal clock circuitry in the ISO120/121 precision isola-
tion amplifier (ISO amp) can be synchronized to an external
clock signal. Synchronization to an external clock can be
used to eliminate beat frequencies in multichannel systems
or for rejection of specific AC signals and their harmonics鈥?/div>
see the ISO120/121 product data sheet, PDS-820.
The external clock signal can be directly connected to the
ISO120/121 if it is a sine or triangle wave of the proper
amplitude. At clock frequencies above 400kHz, a square
wave external clock can also be directly connected to the
ISO120/121. Other clock signals can be used with the
addition of the signal conditioning circuit shown in Figure 2.
SYNCHRONIZING TO A SINE
OR TRIANGLE WAVE EXTERNAL CLOCK
The ideal external clock signal for the ISO120/121 is a
鹵4V
sine wave or
鹵4V,
50% duty-cycle triangle wave. The
ext
osc
pin of the ISO120/121 can be driven directly with a
鹵3V
to
鹵5V
sine or 25% to 75% duty-cycle triangle wave and the
ISO amp鈥檚 internal modulator/demodulator circuitry will
synchronize to the signal.
EXTERNAL CLOCK
FREQUENCY RANGE
400kHz to 700kHz
200kHz to 400kHz
100kHz to 200kHz
50kHz to 100kHz
20kHz to 50kHz
10kHz to 20kHz
5kHz to 10kHz
C
1
, C
2
ISO120/121
MODULATOR, DEMODULATOR
EXTERNAL CAPACITOR
none
500pF
1000pF
2200pF
4700pF
0.01碌F
0.022碌F
TABLE I. Recommended ISO120/121 External Modulator/
Demodulator Capacitor Values vs External Clock
Frequency.
EXTERNAL CLOCK
FREQUENCY RANGE
400kHz to 700kHz
200kHz to 400kHz
100kHz to 200kHz
50kHz to 100kHz
20kHz to 50kHz
10kHz to 20kHz
5kHz to 10kHz
C
X
30pF
180pF
680pF
1800pF
3300pF
0.01碌F
0.022碌F
TABLE II. Recommended C
X
Values vs Frequency for
Figure 2 Circuit.
Optional External
Modulator
Capacitor
C
1H
C
1
C
1L
Optional External
Demodulator
Capacitor
C
2H
C
2
C
2L
100碌A(chǔ)
200k鈩?/div>
V
IN
Sense
Amp
150pF
1pF
1pF
100碌A(chǔ)
150pF
Sense
Amp
200k鈩?/div>
V
O
1pF
100碌A(chǔ)
1pF
100碌A(chǔ)
Bucket-
Brigade
Sample/
Hold
G = 2蟺
30k鈩?/div>
Ext
Osc
16k鈩?/div>
16k鈩?/div>
50pF
ISO120/121
Modulator
ISO120/121
Demodulator
FIGURE 1. ISO120/121 Block Diagram Showing Internal Clamp and Filter Circuitry at the Ext Osc Pin.
1
漏
1991 Burr-Brown Corporation
AB-021
Printed in U.S.A. January, 1991
AB-021相關(guān)型號(hào)PDF文件下載
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英文版
AB-001 - INCREASING INA117 DIFFERENTIAL INPUT RANGE
ETC
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英文版
AB-002 - MAKE A PRECISION CURRENT SOURCE OR CURRENT SINK
ETC
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英文版
AB-003 - VOLTAGE-REFERENCE FILTERS
ETC
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英文版
AB-004 - MAKE A PRECISION -10V REFERENCE
ETC
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英文版
AB-005 - Make A Precision -10V Reference
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英文版
AB-006 - Make a -10V to +10V Adjustable Precision Voltage So...
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AB-007 - CLASSICAL OP AMP OR CURRENT-FEEDBACK OP AMP?
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英文版
AB-008 - AC COUPLING INSTRUMENTATION AND DIFFERENCE AMPLIFIE...
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英文版
AB-009 - SINGLE-SUPPLY OPERATION OF ISOLATION AMPLIFIERS
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英文版
AB-010 - -200V DIFFERENCE AMPLIFIER WITH COMMON-MODE VOLTAGE...
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AB-011 - LOW POWER SUPPLY VOLTAGE OPERATION OF REF102 10.0V ...
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英文版
AB-012 - BOOST ISO120 BANDWIDTH TO MORE THAN 100kHz
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AB-013 - INCREASING ADC603 INPUT RANGE
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英文版
AB-014 - INPUT OVERLOAD PROTECTION FOR THE RCV420 4-20mA CUR...
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英文版
AB-015 - EXTENDING THE COMMON-MODE RANGE OF DIFFERENCE AMPLI...
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AB-016 - BOOST AMPLIFIER OUTPUT SWING WITH SIMPLE MODIFICATI...
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英文版
AB-017 - Sallen-Key Low-Pass Filter Design Program
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英文版
AB-018 - 0 TO 20mA RECEIVER USING RCV420
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AB-019 - USING THE ADS7800 12 BIT ADC WITH UNIPOLAR INPUT SI...
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英文版
AB-020 - BURR-BROWN SPICE BASED MACROMODELS. REV. F
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