Philips PCF1252-0P-F4, PCF1252-0T-F4, PCF1252-5P, PCF1252-5P-F4, PCF1252-5T-F4 Datasheet

INTEGRATED CIRCUITS

DATA SHEET

PCF1252-X family

Threshold detector and reset generator

Product specification

1998 Apr 16

Supersedes data of 1996 Jan 23

File under Integrated Circuits, IC11

Philips Semiconductors	Product specification
Threshold detector and reset generator	PCF1252-X family

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

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.

	TYPE NUMBER		PACKAGE
		NAME	DESCRIPTION	VERSION
	PCF1252-XP(1)	DIP8	plastic dual in-line package; 8 leads (300 mil)	SOT97-1
	PCF1252-XT(1)	SO8	plastic small outline package; 8 leads; body width 3.9 mm	SOT96-1

Note

1. X = 0 to 9; depending on threshold voltage.

BLOCK DIAGRAM

handbook, full pagewidth

VDD COMIN

8	3
	comparator 2
	+		5
	−		COMOUT
	comparator 1		PCF1252-X
	+		7
	−		POWF
	1.30 V	DELAY	6
			RESET
4		1	2
			MGC915
VSS		CT	SELECT

Fig.1 Block diagram.

1998 Apr 16

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Philips Semiconductors	Product specification
Threshold detector and reset generator	PCF1252-X family

PINNING

	SYMBOL		PIN	DESCRIPTION
	CT		1	connection for the external capacitor
	SELECT		2	select polarity or external reset input
	COMIN		3	comparator input
	VSS		4	ground (0 V)
	COMOUT		5	comparator output
	RESET		6	reset output
			7	power failure signal output
	POWF
	VDD		8	supply voltage

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.

	handbook, halfpage
	CT	1		8	VDD
	SELECT	2
			PCF1252-X	7	POWF
	COMIN	3		6	RESET
	VSS	4		5	COMOUT
			MGC916

Fig.2 Pinning diagram.

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

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Philips Semiconductors					Product specification
Threshold detector and reset generator				PCF1252-X family
LIMITING VALUES
In accordance with the Absolute Maximum Rating System (IEC 134).
SYMBOL	PARAMETER	CONDITIONS	MIN.		MAX.	UNIT
VDD	supply voltage		−0.5		+7.0	V
VI	input voltage		−0.5		VDD + 0.5	V
II	DC clamp-diode current	all pins: VI < −0.5 V	−		20	mA
		or VI > VDD + 0.5 V
IO	output current		−		20	mA
Ptot	total power dissipation		−		150	mW
Tstg	storage temperature		−65		+100	°C
Tamb	operating ambient temperature		−40		+85	°C

HANDLING

Inputs and outputs are protected against electrostatic discharge in normal handling. However, to be totally safe, it is desirable to take normal handling precautions appropriate to handling MOS devices (see “Handling MOS Devices”).

CHARACTERISTICS

VDD = 2.4 to 6.0 V; VSS = 0 V; Tamb = −40 to +85 °C; (see Fig.3); unless otherwise specified.

SYMBOL	PARAMETER	CONDITIONS	MIN.	TYP.	MAX.	UNIT
VDD	supply voltage		2.4	−	6.0	V
VTRIP	Voltage trip-point:	Tamb = 25 °C; note 1
	PCF1252-0		4.70	4.75	4.80	V
	PCF1252-1		4.50	4.55	4.60	V
	PCF1252-2		4.20	4.25	4.30	V
	PCF1252-3		4.00	4.05	4.10	V
	PCF1252-4		3.70	3.75	3.80	V
	PCF1252-5		3.50	3.55	3.60	V
	PCF1252-6		3.20	3.25	3.30	V
	PCF1252-7		3.00	3.05	3.10	V
	PCF1252-8		2.70	2.75	2.80	V
	PCF1252-9		2.50	2.55	2.60	V
IDD	supply current	Tamb = 25 °C;	−	10	15	μA
		VDD = VTRIP + 0.5 V;
		COMIN = VDD;
		see Figs. 4 and 5
VTRIP	voltage trip-point temperature	note 2	−	±100 × 10−6	±400 × 10−6	mV/K
	coefficient
Vhys	voltage trip-point hysteresis		15	30	50	mV

1998 Apr 16

4

Philips Semiconductors							Product specification
	Threshold detector and reset generator					PCF1252-X family
	SYMBOL		PARAMETER	CONDITIONS	MIN.	TYP.	MAX.	UNIT
	COMIN
	VSP		COMIN switch point	Tamb = 25 °C; note 1	1.28	1.30	1.32	V
	VSP		COMIN switch point temperature	note 2	−	±0.1	±0.5	mV/K
			coefficient
	SELECT
	VIL		LOW level input voltage		−	−	0.3VDD	V
	VIH		HIGH level input voltage		0.7VDD	−	−	V
	SELECT and COMIN
	ILI		LOW level leakage input current		−	−	−1.0	μA
	ILI		HIGH level leakage input current		−	−	1.0	μA
		RESET and COMOUT
	POWF,
	IO		output sink current	VO = 0.4 V;	1	3	−	mA
				VDD = 2.4 V;
				see Fig.6
	IO		output source current	VO = 2.0 V;	−0.75	−2	−	mA
				VDD = 2.4 V;
				see Fig.7
	tR		reset time	CCT = 1 nF; note 3	400	1000	2000	μs
	tS		save time	CCT = 1 nF; note 3	40	100	200	μs
	tR/tS		reset to save time ratio		−	10	−
	Cint		CT internal capacitance		−	100	−	pF

Notes

1.Long time stability of COMIN switch point VSP and voltage trip point VTRIP: within 10 years of continuous operation at VDD(max) and an average operating temperature of 55 °C the drift of VSP will not exceed ±10 mV. The maximum drift for VTRIP will not exceed (±VTRIP(typ)/VSP(typ)) 10 mV.

2.Values given per degree Kelvin; tested on a sample basis.

3.Conformance to these specifications is only guaranteed if the slew rate of VDD is less than 25 V/ms.

1998 Apr 16

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