Electronic Components Datasheet Search |
|
AD629BR-REEL7 Datasheet(PDF) 8 Page - Analog Devices |
|
AD629BR-REEL7 Datasheet(HTML) 8 Page - Analog Devices |
8 / 12 page REV. A AD629 –8– APPLICATIONS Basic Connections Figure 29 shows the basic connections for operating the AD629 with a dual supply. A supply voltage of between ± 3 V and ±18 V is applied between Pins 7 and 4. Both supplies should be decoupled close to the pins using 0.1 µF capacitors. 10 µF elec- trolytic capacitors, also located close to the supply pins, may also be required if low frequency noise is present on the power supply. While multiple amplifiers can be decoupled by a single set of 10 µF capacitors, each in amp should have its own set of 0.1 µF capacitors so that the decoupling point can be located physically close to the power pins. REF(–) –IN +IN –VS NC +VS VOUT = ISHUNT RSHUNT REF(+) AD629 21.1k 380k 380k 380k 20k NC = NO CONNECT 0.1 F (SEE TEXT) +VS 3V TO 18V 0.1 F (SEE TEXT) RSHUNT ISHUNT –VS –3V TO –18V 8 7 6 5 1 2 3 4 Figure 29. Basic Connections The differential input signal, which will typically result from a load current flowing through a small shunt resistor, is applied to Pins 2 and 3 with the polarity shown in order to obtain a posi- tive gain. The common-mode range on the differential input signal can range from –270 V to +270 V and the maximum dif- ferential range is ±13 V. When configured as shown, the device operates as a simple gain-of-one differential-to-single-ended amplifier, the output voltage being the shunt resistance times the shunt current. The output is measured with respect to Pins 1 and 5. Pins 1 and 5 (REF(–) and REF(+)) should be grounded for a gain of unity and should be connected to the same low imped- ance ground plane. Failure to do this will result in degraded common-mode rejection. Pin 8 is a no connect pin and should be left open. Single Supply Operation Figure 30 shows the connections for operating the AD629 with a single supply. Because the output can swing to within only about 2 V of either rail, it is necessary to apply an offset to the output. This can be conveniently done by connecting REF(+) and REF(–) to a low impedance reference voltage (some analog- to-digital converters provide this voltage as an output), which is capable of sinking current. Thus, for a single supply of 10 V, VREF might be set to 5 V for a bipolar input signal. This would allow the output to swing ±3 V around the central 5 V reference voltage. Alternatively, for unipolar input signals, VREF could be set to about 2 V, allowing the output to swing from +2 V (for a 0 V input) to within 2 V of the positive rail. OUTPUT = VOUT –VREF VREF REF(–) –IN +IN –VS NC +VS REF(+) AD629 380k 380k 380k 20k NC = NO CONNECT 0.1 F +VS RSHUNT ISHUNT 8 7 6 5 1 2 3 4 VX VY 21.1k Figure 30. Operation with a Single Supply Applying a reference voltage to REF(+) and REF(–) and operating on a single supply will reduce the input common-mode range of the AD629. The new input common-mode range depends upon the voltage at the inverting and noninverting inputs of the internal operational amplifier, labeled VX and VY in Figure 30. These nodes can swing to within 1 V of either rail. So for a (single) supply voltage of 10 V, VX and VY can range between 1 V and 9 V. If VREF is set to 5 V, the permissible common-mode range is +85 V to –75 V. The common-mode voltage ranges can be calculated using the following equation. VVV CM X Y REF ± ( ) =±() − 20 19 / System-Level Decoupling and Grounding The use of ground planes is recommended to minimize the impedance of ground returns (and hence the size of dc errors). Figure 31 shows how to work with grounding in a mixed-signal environment, that is, with digital and analog signals present. In order to isolate low-level analog signals from a noisy digital environment, many data-acquisition components have separate analog and digital ground returns. All ground pins from mixed- signal components such as analog-to-digital converters should be returned through the “high quality” analog ground plane. This includes the digital ground lines of mixed-signal converters that should also be connected to the analog ground plane. This may seem to break the rule of keeping analog and digital grounds separate, but in general, there is also a requirement to keep the voltage difference between digital and analog grounds on a con- verter as small as possible (typically <0.3 V). The increased noise, caused by the converter’s digital return currents flowing through the analog ground plane, will typically be negligible. Maximum isolation between analog and digital is achieved by connecting the ground planes back at the supplies. Note that Figure 31, as drawn, suggests a “star” ground system for the analog circuitry, with all ground lines being connected, in this case, to the ADC’s analog ground. However, when ground planes are used, it is sufficient to connect ground pins to the nearest point on the low impedance ground plane. |
Similar Part No. - AD629BR-REEL7 |
|
Similar Description - AD629BR-REEL7 |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.NET |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |