Os motores de busca de Datasheet de Componentes eletrônicos |
|
ADC081S101 Folha de dados(PDF) 11 Page - National Semiconductor (TI) |
|
|
ADC081S101 Folha de dados(HTML) 11 Page - National Semiconductor (TI) |
11 / 13 page Applications Information (Continued) 5.0 ANALOG INPUTS An equivalent circuit for one of the ADC081S051’s input channels is shown in Figure 7. Diodes D1 and D2 provide ESD protection for the analog inputs. At no time should any input go beyond (V A + 300 mV) or (GND − 300 mV), as these ESD diodes will begin conducting, which could result in erratic operation. The capacitor C1 in Figure 7 has a typical value of 4 pF, and is mainly the package pin capacitance. Resistor R1 is the on resistance of the multiplexer and track / hold switch, and is typically 500 ohms. Capacitor C2 is the ADC081S051 sam- pling capacitor and is typically 26 pF. The ADC081S051 will deliver best performance when driven by a low-impedance source to eliminate distortion caused by the charging of the sampling capacitance. This is especially important when using the ADC081S051 to sample AC signals. Also important when sampling dynamic signals is a band-pass or low-pass filter to reduce harmonics and noise, improving dynamic performance. 6.0 DIGITAL INPUTS AND OUTPUTS The ADC081S051 digital inputs (SCLK and CS) are not limited by the same absolute maximum ratings as the analog inputs. The digital input pins are instead limited to +6.5V with respect to GND, regardless of V A, the supply voltage. This allows the ADC081S051 to be interfaced with a wide range of logic levels, independent of the supply voltage. 7.0 MODES OF OPERATION The ADC081S051 has two possible modes of operation: normal mode, and shutdown mode. The ADC081S051 en- ters normal mode (and a conversion process is begun) when CS is pulled low. The device will enter shutdown mode if CS is pulled high before the tenth falling edge of SCLK after CS is pulled low, or will stay in normal mode if CS remains low. Once in shutdown mode, the device will stay there until CS is brought low again. By varying the ratio of time spent in the normal and shutdown modes, a system may trade-off throughput for power consumption. 7.1 Normal Mode The fastest possible throughput is obtained by leaving the ADC081S051 in normal mode at all times, so there are no power-up delays. To keep the device in normal mode con- tinuously, CS must be kept low until after the 10th falling edge of SCLK after the start of a conversion (remember that a conversion is initiated by bringing CS low). If CS is brought high after the 10th falling edge, but before the 16th falling edge, the device will remain in normal mode, but the current conversion will be aborted, and SDATA will return to TRI-STATE (truncating the output word). Sixteen SCLK cycles are required to read all of a conversion word from the device. After sixteen SCLK cycles have elapsed, CS may be idled either high or low until the next conversion. If CS is idled low, it must be brought high again before the start of the next conversion, which begins when CS is again brought low. After sixteen SCLK cycles, SDATA returns to TRI-STATE. Another conversion may be started, after t QUIET has elapsed, by bringing CS low again. 7.2 Shutdown Mode Shutdown mode is appropriate for applications that either do not sample continuously, or it is acceptable to trade through- put for power consumption. When the ADC081S051 is in shutdown mode, all of the analog circuitry is turned off. To enter shutdown mode, a conversion must be interrupted by bringing CS back high anytime between the second and tenth falling edges of SCLK, as shown in Figure 8. Once CS has been brought high in this manner, the device will enter shutdown mode; the current conversion will be aborted and SDATA will enter TRI-STATE. If CS is brought high before the second falling edge of SCLK, the device will not change mode; this is to avoid accidentally changing mode as a result of noise on the CS line. 20145514 FIGURE 7. Equivalent Input Circuit 20145516 FIGURE 8. Entering Shutdown Mode www.national.com 11 |
Nº de peça semelhante - ADC081S101 |
|
Descrição semelhante - ADC081S101 |
|
|
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 |