Electronic Components Datasheet Search |
|
AS1908C20-T Datasheet(PDF) 7 Page - ams AG |
|
AS1908C20-T Datasheet(HTML) 7 Page - ams AG |
7 / 10 page AS1907/AS1908/AS1909 Datasheet - Application In form atio n www.ams.com/Supervisors/AS1907-09 Revision 1.8 7 - 10 8 Application Information 8.1 Negative Going VCC Transients All devices are effectively immune to short-duration, negative-going VCC transients (glitches). The Maximum Transient Duration vs. Reset Comparator Overdrive graph (see page 5) shows the maximum pulse width that a negative-going VCC transient may typically have without issuing a reset signal. As the amplitude of the transient increases, the maximum allowable pulse width decreases. 8.2 Valid Reset Output If VCC falls below 1V and approaches the minimum operating voltage of 0.7V, push/pull-type reset sinking/sourcing capabilities greatly decrease. High-impedance CMOS-logic inputs connected to RESET can drift to indeterminate voltages, although this is normally not a problem since most microprocessors do not operate at VCC < 1V. For the AS1908, where RESET must be valid to VCC = 0, a 100k Ω pull-up resistor between RESET and VCC (see Figure 1 on page 1) will hold RESET high if VCC falls below 0.7V. For the AS1907, where RESET must be valid down to 0V, add a pull-down resistor between RESET and GND (see Figure 1 on page 1) to eliminate stray leakage currents and hold RESET low. A pull-down resistor of 100k Ω is large enough not to load RESET yet small enough to pull it low. Since the AS1909 has an open-drain, active-low output, it typically uses a pull-up resistor. With this device, RESET will most likely not maintain an active condition, but will drift to a non-active level due to the pull-up resistor and the reduced sinking capability of the open drain device. Therefore, this device is not recommended for applications where the RESET pin is required to be valid down to VCC = 0. 8.3 Bi-Directional Microprocessor Interface The RESET output on the AS1909 is open-drain, thus this device can interface easily with microprocessors that have bi-directional reset pins, such as the Motorola 68HC11. Connect the RESET output of this device directly to the microprocessor’s RESET I/O pin with a single pull-up resistor to allow either device to assert reset (see Figure 1 on page 1). 8.4 Layout Considerations The devices require proper layout and design procedures for optimum performance. Short, wide traces should be used to reduce stray inductance and capacitance. Bypass capacitors should be as close to the device as possible. Large ground planes should be used wherever possible. Table 5. Reset Thresholds Reset Thresholds TAMB = +25ºC TAMB = -40 to +125ºC Suffix Min Typ Max Min Max 25 2.478 2.50 2.523 2.43 2.58 24 2.378 2.40 2.422 2.33 2.47 23 2.279 2.30 2.321 2.23 2.37 22 2.180 2.20 2.220 2.13 2.27 21 2.081 2.10 2.119 2.04 2.18 20 1.982 2.00 2.018 1.94 2.06 19 1.883 1.90 1.917 1.84 1.96 18 1.784 1.80 1.816 1.75 1.85 17 1.685 1.70 1.715 1.65 1.75 16 1.586 1.60 1.614 1.55 1.65 |
Similar Part No. - AS1908C20-T |
|
Similar Description - AS1908C20-T |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.COM |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | 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 |