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Número de pieza | LTC6943 | |
Descripción | Dual Precision Instrumentation Switched Capacitor Building Block | |
Fabricantes | Linear | |
Logotipo | ||
Hay una vista previa y un enlace de descarga de LTC6943 (archivo pdf) en la parte inferior de esta página. Total 16 Páginas | ||
No Preview Available ! FEATURES
■ Low Power, IS = 60µA(Max)
■ Robust, Latch Up Proof
■ Instrumentation Front End with 120dB CMRR
■ Precise, Charge-Balanced Switching
■ Operates from 5V to 18V
■ Internal or External Clock
■ Operates up to 5MHz Clock Rate
■ Two Independent Sections with One Clock
■ Tiny SSOP-16 PaUckage
APPLICATIO S
■ Ultra Precision Voltage Inverters, Multipliers
and Dividers
■ V–F and F–V Converters
■ Sample-and-Hold
■ Current Sources
■ Precision Instrumentation Amplifiers
, LTC and LT are registered trademarks of Linear Technology Corporation.
LTCMOS is a trademark of Linear Technology Corporation.
TYPICAL APPLICATIO
Precision Voltage Controlled Current Source
with Ground Referred Input and Output
INPUT
0V TO 3.7V
5V
3+ 5
LTC2050
4– 2
1
0.68µF
5V
1k 3
1/2 LTC6943
76
9
1µF 1µF
10
1k
12
15
0.001µF
11
14
IOUT =
VIN
1000Ω
OPERATES FROM A
SINGLE 5V SUPPLY
6943 • TA01a
LTC6943
Micropower, Dual Precision
Instrumentation Switched
Capacitor Building Block
DESCRIPTIO
The LTC®6943 is a monolithic, charge-balanced, dual
switched capacitor instrumentation building block. A pair
of switches alternately connects an external capacitor to
an input voltage and then connects the charged capacitor
across an output port. The internal switches have a
break-before-make action. An internal clock is provided
and its frequency can be adjusted with an external
capacitor. The LTC6943 can also be driven with an external
CMOS clock.
The LTC6943, when used with low clock frequencies,
provides ultra precision DC functions without requiring
precise external components. Such functions are
differential voltage to single-ended conversion, voltage
inversion, voltage multiplication and division by 2, 3, 4, 5,
etc.
The LTC6943 is manufactured using Linear Technology’s
enhanced LTCMOSTM silicon gate process, and it is func-
tionally compatible with the LTC1043.
Precision Current Sensing in Supply Rails
POSITIVE OR
NEGATIVE RAIL
I
E
RSHUNT
11
1/2 LTC6943
12
10
1µF
9
1µF
E I= E
RSHUNT
67
14
0.01µF
15
6943 • TA01b
6943f
1
1 page TEST CIRCUITS
Test Circuit 1. Leakage Current Test
(6, 11, 5, 16)
A
+
0V TO 10V
(7, 12, 4, 13)
(9, 10, 1, 2)
NOTE: TO OPEN SWITCHES,
S1 AND S3 PIN 14,
SHOULD BE CONNECTED
TO V–. TO OPEN S2, S4, THE
COSC PIN 14 SHOULD BE
CONNECTED TO V+ COSC
6943 • TC01
Test Circuit 3. Oscillator Frequency, fOSC
(TEST PIN) 1
V+
+3
4
+
IV
5
LTC6943
V–
15
COSC 14
6943 • TC03
APPLICATIO S I FOR ATIO
Common Mode Rejection Ratio (CMRR)
The LTC6943, when used as a differential to single-ended
converter rejects common mode signals and preserves
differential voltages (Figure 1). Unlike other techniques,
the LTC6943’s CMRR does not degrade with increasing
common mode voltage frequency. During the sampling
mode, the impedance of Pins 1, 2 (and 9, 10) should be
balanced, otherwise, common mode signals will appear
differentially. The value of the CMRR depends on the value
of the sampling and holding capacitors (CS, CH) and on the
sampling frequency. Since the common mode voltages
are not sampled, the common mode signal frequency can
well exceed the sampling frequency without experiencing
aliasing phenomena. The CMRR of Figure 1 is measured
by shorting Pins 6 and 11 and by observing, with a
LTC6943
Test Circuit 2. RON Test
(6, 11, 5, 16)
(7, 12, 4, 13)
+
VIN
100µA to 1mA
CURRENT SOURCE
(9, 10, 1, 2)
A
6943 • TC02
Test Circuit 4. CMRR Test
6 7 VOUT
89
1µF
10
CAPACITORS ARE
1µF NOT ELECTROLYTIC
11 12
+ V– ≤ VCM ≤ V+
( )CMRR = 20 LOG
VCM
VOUT
NOTE: FOR OPTIMUM CMRR, THE COSC SHOULD
BE LARGER THAN 0.0047µF, AND
THE SAMPLING CAPACITOR ACROSS
PINS 9 AND 10 SHOULD BE PLACED
OVER A SHIELD TIED TO PIN 8
6943 • TC04
1/2 LTC6943
67
+
VD
C+ 9
CS
C– 10
+
VD
CH
+
VCM
11
12
CS, CH ARE MYLAR OR POLYPROPYLENE
6943 • AI01
Figure 1. Differential to Single-Ended Converter
6943f
5
5 Page LTC6943
TYPICAL APPLICATIO S
50MHz Thermal RMS/DC Converter
5V 5V
300mV–
10VRMS
INPUT
BRN
T1
30k**
30k**
10k
0.01µF
10k
RED RED
T2
3
1/2 LTC6943
5
4
1
1µF 1µF
2 14
16
1µF
BRN
15
13
GRN GRN
5V
3+ 8
LT1013
2–
1µF
4
0.01µF
CALIBRATION ADJUST
5V
1 20k 5 +
100k*
LT1013
6–
301Ω* 10k
7 DC OUTPUT
0V TO 3.5V
10k
10k
2% ACCURACY DC-50MHZ
100:1 CREST FACTOR CAPABILITY
T1 – T2 = YELLOW SPRINGS INST. CO.
THERMISTOR COMPOSITE
ENCLOSE T1 AND T2 IN STYROFOAM
*1% RESISTOR
**0.1% RESISTOR
6943 • TA13
2k
1µF
Single Supply Precision Linearized Platinum RTD Signal Conditioner
5V
3+ 8
1/2 LT1013
2– 4
1
0.1µF
1/2 LTC6943
6
7
250k*
10k* 2.4k 5V
2.74k*
50k
ZERO
ADJUST
LT1009
2.5V
8.25k*
3
1/2 LTC6943
4
5
9
1µF
10
887Ω*
1
1µF
2
(LINEARITY CORRECTION LOOP)
0V TO 4V = 0°C TO 400°C
5+
± 0.05°C
7
1/2 LT1013
6–
1k
GAIN
5k
LINEARITY
ADJUST
ADJUST
1µF
8.06k*
11 12
13 16
1k*
Rp Rp = ROSEMOUNT 118MFRTD
1mA 100Ω
*1% FILM RESISTOR
AT 0°C
14
0.01µF
15
TRIM SEQUENCE:
SET SENSOR TO 0°C VALUE. ADJUST ZERO FOR 0V OUT
SET SENSOR TO 100°C VALUE. ADJUST GAIN FOR 1000V OUT
SET SENSOR TO 400°C VALUE. ADJUST LINEARITY FOR 4000V OUT
REPEAT AS REQUIRED
6943 • TA14
6943f
11
11 Page |
Páginas | Total 16 Páginas | |
PDF Descargar | [ Datasheet LTC6943.PDF ] |
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