MIC2778-1YM5 TR Microchip

MIC2778 Micrel MIC2778 Voltage Monitor with Adjustable Hysteresis General Description Features The MIC2778 is a voltage monitoruniquely designed to Optimized for PDAs, cellular telephones, pagers, detect two separate voltage thresholdscombined with a and other battery-powered devices delay generator and logic. It is designed for monitoring the Independently adjustable high- and battery supply of portable digital systems, particularly PDAs, low-voltage thresholds pagers, and cellular telephones. Internal logic prevents battery-voltage-uctuation chatter High 2% voltage threshold accuracy 1% available High- and low-voltage thresholds can be adjusted inde- Built in 140ms (minimum) delay deglitches output pendently, allowing for wide hysteresis. Voltage detection Extremely low 1A typical supply current thresholds are accurate to 2%. For applications not requiring built-in delay, see MIC841 If the battery voltage falls below the low-voltage threshold, Immune to brief power supply transients the output (RST) is asserted and latched, preventing system 5-lead SOT-23 package operation until the battery is replaced or recharged. Internal logic prevents the output from chattering due to battery recovery or load removal. The output is asserted for 140ms Applications (minimum) when a fresh battery is inserted. For applications PDAs not requiring built-in delay, see MIC841. Pagers The ICs power supply input is separate from the detector Cordless phones inputs, allowing the MIC2778 to be powered from a down- Consumer electronics stream supply, such a boost converter. Supply current is Embedded controllers extremely low (1A, typical), making it ideal for portable Personal electronics applications. A high-precision 1% grade is available. The MIC2778 is sup- plied in Micrels IttyBitty 5-lead SOT-23-5 package. Ordering Information Part Number Accurary Temperature Range Package Standard Marking Pb-Free Marking MIC2778-2BM5 UFB MIC2778-2YM5 UFB* 2% -40C to +85C SOT-23-5 MIC2778-1BM5 UFA MIC2778-1YM5 UFA* 1% -40C to +85C SOT-23-5 * Underscore indicates a Pb-Free part. Typical Application V OUT MIC5207-3.0BM5 3.0V OUT IN 470pF MIC2778 Li-Ion 4.7F 100k B Y P 604k Cell VDD R ST E N 1% GND LTH 56k HTH GND 1% 340k V = 3.6V 1% BAT(hi) V = 3.1V BAT(lo) Cellular Telephone Battery Monitor IttyBitty is a trademark of Micrel, Inc. Micrel, Inc. 2180 Fortune Drive San Jose, CA 95131 USA tel + 1 (408) 944-0800 fax + 1 (408) 474-1000 MIC2778 Micrel Pin Conguration LTH GND HTH 3 2 1 4 5 R ST VDD SOT-23-5 (M5) Pin Description Pin Number Pin Name Pin Function 1 HTH High-Voltage Theshold (Input): Analog input to a comparator. When the level on this pin initially rises above V , the delay generator cycles and the RST REF remains low for a minimum of 140ms. 2 GND Ground 3 LTH Low-Voltage Threshold (Input): Analog input to a comparator. This is the voltage monitor input assigned to detect a low voltage condition. When the level on this pin falls below V , RST is asserted and the condition is REF latched until V > V . HTH REF 4 RST Reset (Output): Active-low, open-drain output. This output is asserted and latched when V <V , indicating a low voltage condition. This state LTH REF remains latched until V > V . HTH REF 5 VDD Power Supply (Input): Independent supply input for internal circuitry. M9999-011405 2 January 2005