Datasheet AD215 (Analog Devices) - 10

AD215 Input Gain Adjustments for the Inverting Mode USING ISOLATED POWER
Figure 17 shows a suggested inverting gain adjustment circuit. Each AD215 provides an unregulated, isolated bipolar power In this circuit, gain adjustment is made using a potentiometer source of ± 15 V dc @ ± 10 mA, referred to the input common. (R This source may be used to power various ancillary components P) in the feedback loop. The adjustments are effective for all gains in the 1 to 10 V/V range. such as signal conditioning and/or adjustment circuitry, refer- ences, op amps or remote transducers. Figure 19 shows typical connections.
R R R IN C F FB 4 CF 47pF R IN– AD215 F IN– 3 OUT HI 3 OUT HI 1k
Ω
OUTPUT 38 IN+ IN+ OUTPUT 38 1 1 FILTER, FILTER, FB BUFFER BUFFER 4 V AND SIGNAL AND IN COM TRIM OUT LO TRIM 2 37 IN COM OUT LO CIRCUITRY 2 CIRCUITRY 37 TRIM 36 TRIM LOAD 36 +VISO +VS AD215 COM 6 42 +15V dc 43 C1 PWR 1.5k
Ω
PWR 430kHz 2.2µF 6.8µF ISOLATED RTN COM RTN POWER 43 DC C2 OSCIL- 1.5k
Ω
–V SUPPLY 6.8µF ISO LATOR –V 2.2µF S 5 44 –15V dc
Figure 17. Gain Adjustment for Inverting Configuration For an approximate ± 1% gain trim range, Figure 19. Using the Isolated Power Supplies × R R = RIN F X + RIN RF
PCB LAYOUT FOR MULTICHANNEL APPLICATIONS
The pin out of the AD215 has been designed to easily facilitate and select multichannel applications. Figure 20a shows a recommended RC = 0.02 × RIN circuit board layout for a unity gain configuration. while R
PWR
F < 10 kΩ
RTN
CF = 47 pF
+15V dc –15V dc SUPPLY BYPASS
Note: R
CAPACITORS FOR
F and RIN should have matched temperature coefficient
2.2µF EVERY FOUR
drift characteristics.
2.2µF AD215s Output Offset Adjustments 38 OUT HI 36 0 42 44
Figure 18 illustrates one method of adjusting the output offset
TRIM 0 37 43
voltage. Since the AD215 exhibits a nominal output offset of –35 mV, the circuit shown was chosen to yield an offset correc-
38 OUT HI 36 1 42 44
tion of 0 mV to +73 mV. This results in a total output offset
TRIM 1 37
range of approximately –35 mV to +38 mV.
43 38 OUT HI 36 2 42 44 TRIM 2 ANALOG IN– 37 STAR 3 OUT HI 43 GROUND IN+ 38 1 38 OUT HI3 LOW-PASS 36 42 44 FB OUTPUT R 4 FILTER, BUFFER T TRIM 3 (150k
Ω
) 37 TRIM 1M
Ω
RP2 43 IN COM 36 2 10k
Ω
RS 2.2µF 33k
Ω
0.01µF 100k
Ω
2.2µF OUT LO 37 +15V 42 IN +15V dc
Figure 20a. PCB Layout for Unity Gain
AD215 2.2µF PWR RTN 43 COM 2.2µF –15V –15V dc CAUTION IN 44
The AD215 design does not provide short-circuit protection of its isolated power supply. A current limiting resistor should be Figure 18. Output Offset Adjustment Circuit placed in series with the supply terminals and the load in order
Output Gain Adjustments
to protect against inadvertent shorts. Since the output amplifier stage of the AD215 is fixed at unity gain, any adjustments can be made only in a subsequent stage. REV. 0 –9–