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MAX6400 Datasheet(PDF) 5 Page - Maxim Integrated Products |
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MAX6400 Datasheet(HTML) 5 Page - Maxim Integrated Products |
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5 / 9 page 
Detailed Description Reset Output A microprocessor’s (µP’s) reset input starts the µP in a known state. These µP supervisory circuits assert reset to prevent code execution errors during power-up, power-down, or brownout conditions. RESET is guaranteed to be a logic low for VCC down to 1V. Once VCC exceeds the reset threshold, an internal timer keeps RESET low for the reset timeout period; after this interval, RESET goes high. If a brownout condition occurs (VCC dips below the reset threshold), RESET goes low. Any time VCC goes below the reset threshold, the internal timer resets to zero, and RESET goes low. The internal timer starts after VCC returns above the reset threshold, and RESET remains low for the reset timeout period. The manual reset input (MR) can also initiate a reset, see the Manual Reset Input section. The MAX6401/ MAX6404 have active-high RESET outputs that are the inverse of the MAX6400/MAX6402/MAX6403/MAX6405 outputs (Figure 1). Manual Reset Input Many µP-based products require manual reset capabil- ity, allowing the operator, a test technician, or external logic circuit to initiate a reset. A logic low on MR asserts reset. Reset remains asserted while MR is low, and for the reset active timeout period (tRP) after MR returns high. This input has an internal 50k Ω pullup resistor, so it can be left open if it is not used. MR can be driven with TTL or CMOS logic levels, or with open-drain/col- lector outputs. Connect a normally open momentary switch from MR to GND to create a manual reset func- tion; external debouncing circuitry is not required. If MR is driven from long cables or if the device is used in a noisy environment, connect a 0.1µF capacitor from MR to ground to provide additional noise immunity (see Figure 1). Applications Information Interfacing to µP with Bidirectional Reset Pins Since the RESET output on the MAX6402/MAX6405 is open-drain, these devices interface easily with (µPs) that have bidirectional reset pins. Connecting the µP supervisor’s RESET output directly to the microcon- troller’s (µC’s) RESET pin with a single pullup resistor allows either device to assert reset (Figure 2). Negative-Going VCC Transients These devices are relatively immune to short-duration, negative-going VCC transients (glitches). The Typical Operating Characteristics show the Maximum Transient Duration vs. Reset Threshold Overdrive graph, for which reset pulses are not gener- µP Supervisory Circuits in 4-Bump (2 ✕ 2) Chip-Scale Package _______________________________________________________________________________________ 5 PIN MAX6400/MAX6402 MAX6403/MAX6405 MAX6401/MAX6404 NAME FUNCTION A1 A1 GND Ground B1 — RESET Active-Low Reset Output, (Open-Drain or Push-Pull). RESET is asserted low when the VCC input is below the selected reset threshold. RESET remains low for the reset timeout period after VCC exceeds the device reset threshold. Open- drain outputs require an external pullup resistor. — B1 RESET Active-High Reset Output. RESET remains high while VCC is below the reset threshold and for at least 100ms after VCC rises above the reset threshold. B2 B2 MR Active-Low Manual Reset. Internal 50k Ω pullup to VCC. Pull low to assert a reset. Reset remains asserted as long as MR is low and for the reset timeout period after MR goes high. Leave unconnected or connect to VCC if unused. A2 A2 VCC Supply Voltage and Input for the Reset Threshold Monitor Pin Description |
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