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PCF1252-X Dataheets PDF



Part Number PCF1252-X
Manufacturers NXP
Logo NXP
Description Threshold detector and reset generator
Datasheet PCF1252-X DatasheetPCF1252-X Datasheet (PDF)

INTEGRATED CIRCUITS DATA SHEET PCF1252-X family Threshold detector and reset generator Product specification Supersedes data of 1996 Jan 23 File under Integrated Circuits, IC11 1998 Apr 16 Philips Semiconductors Product specification Threshold detector and reset generator FEATURES • Very low current consumption, typically 10 µA • 10 factory programmed threshold voltages available covering trip voltages from 4.75 to 2.55 V • ±50 mV trip point accuracy over full temperature range • Variable RES.

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INTEGRATED CIRCUITS DATA SHEET PCF1252-X family Threshold detector and reset generator Product specification Supersedes data of 1996 Jan 23 File under Integrated Circuits, IC11 1998 Apr 16 Philips Semiconductors Product specification Threshold detector and reset generator FEATURES • Very low current consumption, typically 10 µA • 10 factory programmed threshold voltages available covering trip voltages from 4.75 to 2.55 V • ±50 mV trip point accuracy over full temperature range • Variable RESET delay • RESET pulse polarity selection • Defined outputs at 0.6 V (typ.) • Comparator for second level detection (e.g. overvoltage detection) • Advance warning of power fail • Operating temperature range −40 to +85 °C. ORDERING INFORMATION PACKAGE TYPE NUMBER NAME PCF1252-XP(1) PCF1252-XT(1) Note 1. X = 0 to 9; depending on threshold voltage. BLOCK DIAGRAM DIP8 SO8 DESCRIPTION plastic dual in-line package; 8 leads (300 mil) PCF1252-X family GENERAL DESCRIPTION The PCF1252-Xs are low-power CMOS voltage threshold detectors designed especially for supervision of microcontroller/microprocessor systems for detection of power-on/off conditions and generation of a system reset pulse. The PCF1252-X also provides a POWF (power fail) output which is activated at a precise factory-programmed trip point. A system RESET output has a built-in delay with duration determined by an external capacitor (CCT). A second comparator (comparator 2) has been included to enable the possibility of a second monitoring point in the system. VERSION SOT97-1 SOT96-1 plastic small outline package; 8 leads; body width 3.9 mm handbook, full pagewidth VDD 8 COMIN 3 comparator 2 + − comparator 1 + − 5 COMOUT PCF1252-X 7 POWF 1.30 V DELAY 6 RESET 4 VSS 1 CT 2 MGC915 SELECT Fig.1 Block diagram. 1998 Apr 16 2 Philips Semiconductors Product specification Threshold detector and reset generator PINNING SYMBOL CT SELECT COMIN VSS COMOUT RESET POWF VDD PIN 1 2 3 4 5 6 7 8 DESCRIPTION connection for the external capacitor select polarity or external reset input comparator input ground (0 V) comparator output reset output power failure signal output supply voltage handbook, halfpage PCF1252-X family CT SELECT COMIN VSS 1 2 8 VDD 7 POWF RESET COMOUT PCF1252-X 3 4 MGC916 6 5 Fig.2 Pinning diagram. FUNCTIONAL DESCRIPTION (see Fig.1) The PCF1252-X contains: • A precise factory-programmed voltage reference • Two comparators • A delay circuit. The PCF1252-X family is comprised of 10 versions with different factory-programmed voltage trip-points (VTRIP), see Chapter “Characteristics”. Supply The supply voltage (VDD) is internally divided before being compared, via comparator 1, with the internal reference voltage. POWF (see Fig.3) The POWF output is: • LOW, if VDD is below VTRIP • HIGH, if VDD is above VTRIP. Power-on reset (SELECT = LOW) As VDD rises past VTRIP, a positive reset pulse is generated at RESET. The duration of the reset pulse (tR) is determined by the value of the external capacitor (CCT; maximum 1 µF, see Fig.8) connected to CT. With no external capacitor connected, CCT assumes a minimum value of 100 pF. If SELECT is HIGH, the reset pulse is inverted. Power failure During a power-off condition (VDD < VTRIP), POWF goes LOW. After a time delay (tS), also determined by CCT, RESET goes HIGH. Any POWF assertion (VDD < VTRIP) will result in a subsequent RESET pulse. Voltage trip-point By selecting the voltage trip-point slightly higher than the minimum operating voltage of the microcontroller/microprocessor, there is sufficient time for data storage before the power actually fails. In order to prevent oscillations around the voltage trip-point, a small hysteresis has been included, resulting in a power-on switching point that is higher than the voltage trip-point (minimum of 15 mV). The voltage trip-point refers to the value at which power-off is signalled. COMIN Input to the second comparator (comparator 2). When used in conjunction with an external voltage divider, this allows a second point in the system to be monitored. This input has no built-in hysteresis. When not in use connect to VDD. COMOUT will be LOW or HIGH depending on the voltage at COMIN: • COMOUT = HIGH, if voltage at COMIN is above the switch point VSP (typically 1.30 V). • COMOUT = LOW, if voltage at COMIN is below the switch point VSP (typically 1.30 V). 1998 Apr 16 3 Philips Semiconductors Product specification Threshold detector and reset generator LIMITING VALUES In accordance with the Absolute Maximum Rating System (IEC 134). SYMBOL VDD VI II IO Ptot Tstg Tamb HANDLING PARAMETER supply voltage input voltage DC clamp-diode current output current total power dissipation storage temperature operating ambient temperature all pins: VI < −0.5 V or VI > VDD + 0.5 V CONDITIONS −0.5 −0.5 − − − −65 −40 MIN. PCF1252-X family MAX. +7.0 VDD + 0.5 20 20 150 +100 +85 V V UNIT mA mA mW °C °C Inputs and outputs are protected against electrostatic discharge in nor.


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