Philips PCF1252-X DATASHEETS

INTEGRATED CIRCUITS

DATA SH EET

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 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

TYPE NUMBER

NAME DESCRIPTION VERSION

PCF1252-XP
PCF1252-XT

(1)
(1)

DIP8 plastic dual in-line package; 8 leads (300 mil) SOT97-1

SO8 plastic small outline package; 8 leads; body width 3.9 mm SOT96-1

Note

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

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.

PACKAGE

BLOCK DIAGRAM

handbook, full pagewidth

V

COMIN

DD

83

42

V

SS

comparator 2

+

−

comparator 1

+

−

1.30 V

PCF1252-X

DELAY

1

CT SELECT

MGC915

5

COMOUT

7

POWF

6

RESET

Fig.1 Block diagram.

1998 Apr 16 2

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
V

SS

4 ground (0 V)
COMOUT 5 comparator output
RESET 6 reset output
POWF 7 power failure signal output
V

DD

8 supply voltage

handbook, halfpage

1

CT

SELECT

COMIN

2

PCF1252-X

3
4

V

SS

Fig.2 Pinning diagram.

MGC916

V

8

POWF

7

RESET

6

COMOUT

5

DD

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 (V

TRIP

see Chapter “Characteristics”.

Supply

The supply voltage (V

) is internally divided before being

DD

compared, via comparator 1, with the internal reference
voltage.

POWF (see Fig.3)
The POWF output is:

• LOW, if VDD is below V

• HIGH, if VDD is above V

TRIP

TRIP

.

Power-on reset (SELECT = LOW)

As V

rises past V

DD

, a positive reset pulse is generated

TRIP

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.

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 V

. COMOUT will be LOW or HIGH

DD

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).

Power failure

During a power-off condition (V

DD<VTRIP

), POWF goes
LOW. After a time delay (tS), also determined by CCT,
RESET goes HIGH. Any POWF assertion (VDD<V

TRIP

)

will result in a subsequent RESET pulse.

1998 Apr 16 3

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

V

DD

V

I

I

I

I

O

P

tot

T

stg

T

amb

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

supply voltage −0.5 +7.0 V
input voltage −0.5 VDD+ 0.5 V
DC clamp-diode current all pins: VI< −0.5 V

− 20 mA

or VI>VDD+ 0.5 V
output current − 20 mA
total power dissipation − 150 mW
storage temperature −65 +100 °C
operating ambient temperature −40 +85 °C

“Handling MOS Devices”

).

CHARACTERISTICS

= 2.4 to 6.0 V; VSS=0V; T

V

DD

= −40 to +85 °C; (see Fig.3); unless otherwise specified.

amb

SYMBOL PARAMETER CONDITIONS MIN. TYP. MAX. UNIT

V
V

DD
TRIP

supply voltage 2.4 − 6.0 V
Voltage trip-point: T

=25°C; note 1

amb

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

I

DD

supply current T

=25°C;

amb

VDD=V

TRIP

− 10 15 µA

+ 0.5 V;
COMIN = VDD;
see Figs. 4 and 5

∆V

TRIP

voltage trip-point temperature

note 2 −±100 × 10−6±400 × 10−6mV/K

coefficient

V

hys

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

V
∆V

SP

SP

COMIN switch point T
COMIN switch point temperature

coefficient

SELECT

V

IL

V

IH

LOW level input voltage −− 0.3V
HIGH level input voltage 0.7V

SELECT and COMIN

I

LI

I

LI

LOW level leakage input current −− −1.0 µA
HIGH level leakage input current −− 1.0 µA

POWF, RESET and COMOUT

I

O

I

O

t

R

t

S

t

R/tS

C

int

output sink current VO= 0.4 V;

output source current VO= 2.0 V;

reset time CCT= 1 nF; note 3 400 1000 2000 µs
save time CCT= 1 nF; note 3 40 100 200 µs
reset to save time ratio − 10 −
CT internal capacitance − 100 − pF

Notes

1. Long time stability of COMIN switch point VSP and voltage trip point V
at V
drift for V

and an average operating temperature of 55 °C the drift of VSP will not exceed ±10 mV. The maximum

DD(max)

will not exceed (±V

TRIP

TRIP(typ)/VSP(typ)

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.

=25°C; note 1 1.28 1.30 1.32 V

amb

note 2 −±0.1 ±0.5 mV/K

DD

−−V

DD

V

13 − mA
VDD= 2.4 V;
see Fig.6

−0.75 −2 − mA
VDD= 2.4 V;
see Fig.7

: within 10 years of continuous operation

TRIP

) 10 mV.

1998 Apr 16 5