Os motores de busca de Datasheet de Componentes eletrônicos |
|
ISL26102 Folha de dados(PDF) 9 Page - Intersil Corporation |
|
ISL26102 Folha de dados(HTML) 9 Page - Intersil Corporation |
9 / 21 page ISL26102, ISL26104 9 FN7608.0 October 12, 2012 Circuit Description A key element in the ISL26102/ISL26104 A/D converters is its low noise chopper-stabilized programmable gain amplifier. The amplifier features seven gain settings (2x, 4x, 8x, 16x, 32x, 64x, and 128x). On these gain settings, the amplifier has very high input impedance but has restricted common mode range, which does not extend all the way to the power supply rails. When the gain of 1x is selected, the chopper-stabilized amplifier is bypassed. The modulator input, which is used directly in 1x gain, has a common mode range that extends to the supply rails. But, because of this greater common mode range on the 1x gain setting, the input current is higher than on the other gain settings. The ISL26102 provides the user with two fully differential signal inputs at the multiplexer plus two other internal channel selections, which allow the user to monitor the analog supply voltage of the chip, and the on-chip temperature sensor. The ISL26104 provides the user with two additional fully differential inputs on the multiplexer. The programmable gain amplifier has a passive RC filter on its output. The resistors are located inside the chip on the outputs of the differential amplifier stages. The capacitor (nominally a 100nF C0G ceramic or PPS film (Polyphenylene sulfide)) for the filter is connected to the two CAP pins of the chip. The outputs of the differential amplifier stages of the PGA are filtered before their signals are presented to the delta-sigma modulator. This filter reduces the amount of noise by limiting the signal bandwidth and eliminating the chopping artifacts of the chopped PGA stage. Figure 7 illustrates a block diagram of the programmable gain amplifier. Functional Description Analog Input Span The input span of the A/D converter is determined by the magnitude of the voltage reference and the gain setting selection. The voltage reference magnitude is determined by the voltage difference between the VREF+ and the VREF- pins. This voltage may be as low as 1.5V or as great as the analog supply voltage to the chip. The voltage on the VREF pins is scaled to accept a voltage into the A/D converter on 1x gain of ±0.5 VREF/GAIN where gain is 1. An illustration of the input span when using a 5V VREF is in Figure 8. The figure illustrates that with a VREF = 5V and a gain setting of 1x, the input span will be ±2.5V, which is a fully differential signal. If the programmable gain amplifier gain is set to another value other than 1x, the input span will be reduced by the gain scale factor. With a VREF = 5V and the PGA gain set at 128x, the input span into the ADC will be [±(0.5)5V]/128 = ±19.53mV on a fully differential basis. Digital Filter The output of the delta-sigma modulator in the A/D converter is filtered with a Sinc4 digital filter that includes programmable decimation to achieve a wide range of output word rates. The transfer function of the Sinc4 filter is illustrated in Figure 9. Figure 9 is normalized to 1 being the output word rate. The output word rate can be selected by setting bits in the OWR (Output Word Rate) Register. The converter provides a wide selection of word rates as shown in Table 3. Note that the word rates are based upon an XTALIN/CLOCK of 4.9152MHz. If the clock is a different frequency than 4.9152MHz, the actual output word rate will scale proportionally. TABLE 3. OUTPUT WORD RATE REGISTER SETTINGS DATA RATE (Sps) REGISTER CODE (Hex) 2.5 00 501 10 02 20 03 40 04 80 05 100 0B 160 06 200 0C 320 07 400 0D 640 08 800 0E 1000 11 1280 09 1600 0F 2000 12 2560 0A 3200 10 4000 13 2.50 4.50 1.00 0.00 3.00 AIN+ AIN- VCM 2.500 2.500 0.50 2.00 1.50 3.50 4.00 5.00 FIGURE 8. DIFFERENTIAL INPUT FOR VREF = 5V, GAIN = 1X |
Nº de peça semelhante - ISL26102 |
|
Descrição semelhante - ISL26102 |
|
|
Ligação URL |
Privacy Policy |
ALLDATASHEETPT.COM |
ALLDATASHEET é útil para você? [ DONATE ] |
Sobre Alldatasheet | Publicidade | Contato conosco | Privacy Policy | roca de Link | 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 |