Motor de Búsqueda de Datasheet de Componentes Electrónicos |
|
AD7395AR Datasheet(PDF) 9 Page - Analog Devices |
|
AD7395AR Datasheet(HTML) 9 Page - Analog Devices |
9 / 12 page AD7394/AD7395 –9– REV. 0 OPERATION The AD7394 and AD7395 are a set of pin compatible, dual, 12-bit/10-bit digital-to-analog converters. These single-supply operation devices consume less than 200 microamps of current while operating from power supplies in the +2.7 V to +5.5 V range, making them ideal for battery operated applications. They contain a voltage-switched, 12-bit/10-bit, laser trimmed digital-to-analog converter, rail-to-rail output op amps, two DAC registers and a serial input shift register. The external reference input has constant input resistance independent of the digital code setting of the DAC. In addition, the reference input can be tied to the same supply voltage as VDD, resulting in a maximum output voltage span of 0 to VDD. The serial interface consists of a serial data input (SDI), clock (CLK) and chip select pin ( CS) and two load DAC Register pins (LDA and LDB). A reset (RS) pin is available to reset the DAC register to zero scale or midscale, depending on the digital level applied to the MSB pin. This function is useful for power-on reset or system failure recovery to a known state. Additional power savings are accomplished by activating the SHDN pin resulting in a 1.5 µA maximum consumption sleep mode. D/A CONVERTER SECTION The voltage switched R-2R DAC generates an output voltage dependent on the external reference voltage connected to the REF pin according to the following equation: VOUT = V REF × D 2 N (1) where D is the decimal data word loaded into the DAC register and N is the number of bits of DAC resolution. In the case of the 10-bit AD7395 using a 2.5 V reference, Equation 1 simpli- fies to: VOUT = 2.5 × D 1024 (2) Using Equation 2 the nominal midscale voltage at VOUT is 1.25 V for D = 512; full-scale voltage is 2.497 V. The LSB step size is = 2.5 × 1/1024 = 0.0024 V. For the 12-bit AD7394 operating from a 5.0 V reference Equa- tion 1 becomes: VOUT = 5.0 × D 4096 (3) Using Equation 3 the AD7394 provides a nominal midscale voltage of 2.50 V for D = 2048, and a full-scale output of 4.998 V. The LSB step size is = 5.0 × 1/4096 = 0.0012 V. AMPLIFIER SECTION The internal DAC’s output is buffered by a low power con- sumption precision amplifier. The op amp has a 60 µs typical settling time to 0.1% of full scale. There are slight differences in settling time for negative slewing signals versus positive. Also, negative transition settling time to within the last 6 LSBs of zero volts has an extended settling time. The rail-to-rail output stage of this amplifier has been designed to provide precision perfor- mance while operating near either power supply. Figure 20 shows an equivalent output schematic of the rail-to-rail-ampli- fier with its N-channel pull-down FETs that will pull an output load directly to GND. The output sourcing current is provided by a P-channel pull-up device that can source current to GND terminated loads. N-CH VDD VOUT AGND P-CH Figure 20. Equivalent Analog Output Circuit The rail-to-rail output stage provides more than ±1 mA of out- put current. The N-channel output pull-down MOSFET shown in Figure 20 has a 35 Ω ON resistance, which sets the sink cur- rent capability near ground. In addition to resistive load driving capability, the amplifier has also been carefully designed and characterized for up to 100 pF capacitive load driving capability. REFERENCE INPUT The reference input terminal has a constant input resistance independent of digital code which results in reduced glitches on the external reference voltage source. The high 2.5 M Ω input resistance minimizes power dissipation within the AD7394/ AD7395 D/A converters. The VREF input accepts input voltages ranging from ground to the positive supply voltage VDD. One of the simplest applications, which saves an external reference voltage source, is connection of the VREF terminal to the positive VDD supply. This connection results in a rail-to-rail voltage output span maximizing the programmed range. The reference input will accept ac signals as long as they are kept within the supply voltage range, 0 < VREF < VDD. The reference bandwidth and integral nonlinearity error performance are plotted in the Typical Performance Characteristics section (see Figures 8 and 18). The ratiometric reference feature makes the AD7394/AD7395 an ideal companion to ratiometric analog-to-digital converters such as the AD7896. |
Número de pieza similar - AD7395AR |
|
Descripción similar - AD7395AR |
|
|
Enlace URL |
Política de Privacidad |
ALLDATASHEET.ES |
¿ALLDATASHEET es útil para Ud.? [ DONATE ] |
Todo acerca de Alldatasheet | Publicidad | Contáctenos | Política de Privacidad | Intercambio de Enlaces | Lista de Fabricantes 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 |