Datasheet MC3425P1 Datasheet (Motorola)

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The MC3425 is a power supply supervisory circuit containing all the
necessary functions required to monitor over and undervoltage fault
conditions. These integrated circuits contain dedicated over and
undervoltage sensing channels with independently programmable time
delays. The overvoltage channel has a high current Drive Output for use in
conjunction with an external SCR Crowbar for shutdown. The undervoltage
channel input comparator has hysteresis which is externally programmable,
and an open–collector output for fault indication.

• Dedicated Over and Undervoltage Sensing

• Programmable Hysteresis of Undervoltage Comparator

• Internal 2.5 V Reference

• 300 mA Overvoltage Drive Output

• 30 mA Undervoltage Indicator Output

• Programmable Time Delays

• 4.5 V to 40 V Operation

MAXIMUM RATINGS

Rating Symbol Value Unit

Power Supply Voltage V
Comparator Input Voltage Range (Note 1) V
Drive Output Short Circuit Current I

Indicator Output Voltage V
Indicator Output Sink Current I
Power Dissipation and Thermal Characteristics

Maximum Power Dissipation @ TA = 70°C

Thermal Resistance, Junction–to–Air
Operating Junction Temperature T
Operating Ambient Temperature Range T
Storage Temperature Range T

NOTE: 1. The input signal voltage should not be allowed to go negative by more than 300 mV

NOTE: 1. or positive by more than 40 V, independent of VCC, without device destruction.

CC

IR

OS(DRV)

IND

IND

P

D

R

θJA

J
A

stg

40 Vdc

–0.3 to +40 Vdc

Internally

Limited

0 to 40 Vdc

30 mA

1000

80

+150 °C

0 to +70 °C

–55 to +150 °C

mA

mW

°C/W

Order this document by MC3425/D



POWER SUPPLY SUPERVISORY/

OVER AND UNDERVOLTAGE

PROTECTION CIRCUIT

SEMICONDUCTOR

TECHNICAL DATA

8

1

P1 SUFFIX

PLASTIC PACKAGE

CASE 626

PIN CONNECTIONS

O.V. DRV

O.V. DLY

O.V. Sense

Output

1

2

3

8

V

CC

7

Gnd
U.V. IND

6

Output

Simplified Application

Overvoltage Crowbar Protection, Undervoltage Indication

V

in

DC

Power

Supply

+

C

out

MOTOROLA ANALOG IC DEVICE DATA

MC3425

V

out

Undervoltage
Indication

U.V. Sense

45

(Top View)

U.V. DLY

ORDERING INFORMATION

Operating

Device

MC3425P1 TA = 0° to +70°C Plastic DIP

 Motorola, Inc. 1996 Rev 2

Temperature Range

Package

1

MC3425

ELECTRICAL CHARACTERISTICS

(4.5 V ≤ VCC ≤ 40 V; TA = T

Characteristics Symbol Min Typ Max Unit

REFERENCE SECTION

Sense Trip Voltage (Referenced Voltage)

VCC = 15 V

TA= 25°C
T

to T

low

Line Regulation of V

4.5 V ≤ VCC ≤ 40 V; TJ = 25°C

high

(Note 2)

Sense

Power Supply Voltage Operating Range V
Power Supply Current

VCC = 40 V; TA = 25°C; No Output Loads

O.V. Sense (Pin 3) = 0 V;
U.V. Sense (Pin 4) = V

CC

O.V. Sense (Pin 3) = VCC;

U.V. Sense (Pin 4) = 0 V

INPUT SECTION

Input Bias Current, O.V . and U.V. Sense I
Hysteresis Activation Voltage, U.V. Sense

VCC = 15 V; TA = 25°C;

IH = 10%
IH = 90%

Hysteresis Current, U.V. Sense

VCC = 15 V; TA = 25°C; U.V. Sense (Pin 4) = 2.5 V
Delay Pin Voltage (I

Low State

DLY

= 0 mA)

High State
Delay Pin Source Current

VCC = 15 V; V

DLY

= 0 V

Delay Pin Sink Current

VCC = 15 V; V

DLY

= 2.5V

OUTPUT SECTION

Drive Output Peak Current (TA = 25°C) I
Drive Output Voltage

I

= 100 mA; TA = 25° C

DRV

Drive Output Leakage Current

V

= 0 V

DRV

Drive Output Current Slew Rate (TA = 25°C) di/dt – 2.0 – A/µs
Drive Output VCC Transient Rejection

VCC = 0 V to 15 V at dV/dt = 200 V µs;

O.V. Sense (Pin 3) = 0 V; TA = 25°C
Indicator Output Saturation Voltage

I

= 30 mA; TA = 25°C

IND

Indicator Output Leakage Current

V

OH(IND)

= 40 V
Output Comparator Threshold Voltage (Note 3) V
Propagation Delay Time

(VCC = 15 V; TA = 25°C)
Input to Drive Output or Indicator Output

100 mV Overdrive, C

DLY

= 0 µF

Input to Delay

2.5 V Overdrive (0 V to 5.0 V Step)

NOTES: 2. T

low

3.The V

to T

= 0° to +70°C

high

limits are approximately the V

th(OC)

limits over the applicable temperature range.

Sense

to T

low

V

Reg

I

CC(off)

I

CC(on)

V

V

OL(DLY)

V

OH(DLY)

I

DLY(source)

I

DLY(sink)

DRV(peak)

V

OH(DRV)

I

DRV(leak)

I

DRV(trans)

V

IND(sat)

I

IND(leak)

t

PLH(IN/OUT)

t

PLH(IN//DLY)

[Note 2], unless otherwise noted.)

high

Sense

2.4

2.33

line

CC

– 7.0 15 mV

4.5 – 40 Vdc

– 8.5 10 mA

– 16.5 19 mA

IB

– 1.0 2.0 µA

H(act)

–
–

I

H

9.0 12.5 16 µA

–

VCC–0.5

VCC–0.15

140 200 260 µA

1.8 3.0 – mA

200 300 – mA

VCC–2.5 VCC–2.0 – V

– 15 200 nA

– 1.0 – mA

– 560 800 mV

– 25 200 nA

th(OC)

2.33 2.5 2.63 V

– 1.7 – µs

– 700 – ns

2.5

2.5

0.6

0.8

0.2

2.6

2.63

–
–

0.5
–

(Peak)

Vdc

V

V

2

MOTOROLA ANALOG IC DEVICE DATA

MC3425

Figure 1. Hysteresis Current versus

Hysteresis Activation V oltage

14
12

µ

, HYSTERESIS CURRENT ( A)

H

I

TA = 25°C

10

8.0

6.0

4.0

2.0
0

0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

VCC = 40 V

V

CC

=15V

V

, HYSTERESIS ACTIVATION VOLTAGE (V)

H(act)

VCC = 5.0 V

Figure 3. Hysteresis Current

versus T emperature

15.0

µ

14.0

U.V. Sense = 2.5 V

Figure 2. Hysteresis Activation V oltage

versus T emperature

1.2
V

= Voltage Level at

H(act)

VCC = 5.0 V

1.0

0.8

VCC = 15 V

0.6

0.4

0.2

, HYSTERESIS ACTIVATION VOLTAGE (V)

H(act)

V

VCC = 40 V

0

–55 –25 0 25 50 75 100 125

TA, AMBIENT TEMPERATURE (

which Hysteresis Current
(IH) is 90% of full value.

°

C)

Figure 4. Sense Trip Voltage Change

versus T emperature

V

* = 2.400 V * = 2.500 V * = 2.600 V

Sense

0

–10

13.0

12.0

11.0

, HYSTERESIS CURRENT ( A)

H

I

10.0
–55 –25 0 25 50 75 100 125

TA, AMBIENT TEMPERATURE (

°

C)

Figure 5. Output Delay Time versus

Delay Capacitance

, OUTPUT DELAY TIME (mS)t

DLY

100

10

1.0

0.1

0.01

VCC = 15 V

°

C

TA = 25

t

DLY

=

2.5 C
200 µA

DLY

–20

–30

–40

, SENSE TRIP VOLTAGE CHANGE (mW)

–50

Sense

V

–55 –25 0 25 50 75 100 125

∆

VCC = 15 V
*V

at TA = 25

Sense

TA, AMBIENT TEMPERATURE (°C)

°

C

Figure 6. Delay Pin Source Current

µ

260

240

220

200

, DELAY PIN SOURCE CURRENT ( A)

180

versus T emperature

VCC = 40 V

VCC = 15 V

VCC = 5.0 V

0.001

0.0001 0.001 0.01 0.1 1.0 10
C

, DELAY PIN CAPACITANCE (µF)

DLY

MOTOROLA ANALOG IC DEVICE DATA

160

DLY(source)

I

–55 –25 0 25 50 75 100 125

°

TA, AMBIENT TEMPERATURE (

C)

3

MC3425

Figure 7. Drive Output Saturation Voltage

versus Output Peak Current

5.0

VCC = 15 V

4.0

1.0% Duty Cycle @ 300 Hz

°

C

TA = 25

3.0

2.0

1.0

, DRIVE OUTPUT SATURATION VOLTAGE (V)

0

0 100 200 300 400

OH(DRV)

V

I

DRV(peak)

, DRIVE OUTPUT PEAK CURRENT (mA)

Figure 9. Drive Output Saturation Voltage

versus T emperature

2.500
VCC = 15 V

2.460

2.420

I

DRV(peak)

1.0% Duty Cycle @ 300 Hz

= 200 mA

Figure 8. Indicator Output Saturation Voltage

versus Output Sink Current

0.4

0.3

0.2
VCC = 15 V

°

C

TA = 25

0.1

0

, INDICAT OR OUTPUT SATURATION VOL TAGE (V)

010203040

I

, INDICAT OR OUTPUT SINK CURRENT (mA)

IND(sat)

V

IND

Figure 10. Power Supply Current

versus V oltage

28

Curve O.V. Sense U.V. Sense

AVCCGnd

24

B Gnd V

20
16

CC

A

2.380

2.340

, DRIVE OUTPUT SATURATION VOTLAGE (V)

2.300
–55 –25 0 25 50 75 100 125

OH(DRV)

V

TA, AMBIENT TEMPERATURE (

°

C)

12

8.0

, POWER SUPPLY CURRENT (mA)

4.0

CC

I

0

0 5.0 10 15 20 25 30 35 40

VCC, POWER SUPPLY VOLTAGE (V)

B

TA = 25°C

4

MOTOROLA ANALOG IC DEVICE DATA

MC3425

APPLICATIONS INFORMATION

Figure 11. Overvoltage Protection and

Undervoltage Fault Indication with

Programmable Delay

R1A R1B

8

+

Power

Supply

4.5V to 40V
–

R2A

U.V. Hysteresis = I

t

= 12500 C

DLY

DLY

4

I

H

3

R2B

C

DLY

R1B R2B

H

R1B + R2B R2A

V

CC

U.V.

Sense

O.V.

Sense
O.V.

DLY

275

MC3425

Gnd

, V

O(trip)

U.V.
IND

O.V.
DRV

U.V.
DLY

U.V. Fault
Indicator

6

1

C

DLY

– 2.5 V

1 +

Gnd

R1A

+V

Figure 12. Overvoltage Protection of 5.0 V

Supply with Line Loss Detector

O

V

in

AC Line

+5.0V
Power

Supply

100

U.V. Sense
Pin 4

U.V. DLY
Pin 5

U.V. IND
Pin 6

8

V

15k

4

31

10k

µ

0.01

CC

U.V.

Sense

O.V.

Sense

O.V.
DLY

275

F

MC3425

Gnd

U.V.
IND

O.V.
DRV

U.V.
DLY

VO = 5.0 V
V

= 6.25 V

O(trip)

1.0k

6

0.33

µ

F

2.5V

2.5V

OFF
ON

Line Loss
Output

Figure 13. Overvoltage Audio Alarm Circuit Figure 14. Programmable Frequency Switch

12V

3

O.V.

Sense

MC3425

U.V.

4

Sense

U.V.
DLY

572

µ

F

0.1

8

V

CC

Gnd

O.V.
DRV

O.V.
DLY

Output Pulse when:

f

(input)

1.0k

2.5V

2.5V

ON

OFF

C

1

DLY

+

12V

Power

Supply

12k

2.7k

82k

6.8k

0.1

3

4

µ

O.V.

Sense

U.V.

Sense

U.V.

DLY

F

8
V

CC

MC3425

O.V.
DLY

275

O.V.

DRV

Gnd

+V

Alarm On when:
VO = 13.6 V

1

Ω

100

Gnd

O

Input Signal

I.V. p–p

5.0

µ

F

10k

10k

O.V. Sense

Pin 3

O.V. DLY

Pin 2

O.V. DRV

Pin 1

<

25000 C

1

DLY

MOTOROLA ANALOG IC DEVICE DATA

5

MC3425

CIRCUIT DESCRIPTION

The MC3425 is a power supply supervisory circuit
containing all the necessary functions required to monitor
over and undervoltage fault conditions. The block diagram
is shown below in Figure 15. The Overvoltage (O.V.) and
Undervoltage (U.V.) Input Comparators are both
referenced to an internal 2.5 V regulator. The U.V. Input
Comparator has a feedback activated 12.5 µA current sink
(IH) which is used for programming the input hysteresis
voltage (VH). The source resistance feeding this input (RH)
determines the amount of hysteresis voltage by VH = IHR
= 12.5 × 10–6 RH.

Separate Delay pins (O.V . DL Y, U.V. DLY .) are provided for
each channel to independently delay the Drive and Indicator
outputs, thus providing greater input noise immunity . The two
Delay pins are essentially the outputs of the respective input
comparators, and provide a constant current source,
I

DLY(source)

, of typically 200 µA when the noninverting input
voltage is greater than the inverting input level. A capacitor
connected from these Delay pins to ground, will establish a
predictable delay time (t

) for the Drive and Indicator

DLY

outputs. The Delay pins are internally connected to the
noninverting inputs of the O.V . and U.V. Output Comparators,
which are referenced to the internal 2.5 V regulator.
Therefore, delay time (t

) is based on the constant current

DL Y

source, I
(C

DLY

t

DLY

) to 2.5 V.

DLY(source)

V

=

I

DLY(source)

Figure 5 provides C

, charging the external delay capacitor

ref CDLY

2.5 C

DLY

=

200 µA

values for a wide range of time

DLY

= 12500 C

DL Y

delays. The Delay pins are pulled low when the respective

H

input comparator’s noninverting input is less than the
inverting input. The sink current, I

DLY(sink)

, capability of the
Delay pins is ≥ 1.8 mA and is much greater than the typical
200 µA source current, thus enabling a relatively fast delay
capacitor discharge time.

The Overvoltage Drive Output is a current–limited
emitter–follower capable of sourcing 300 mA at a turn–on
slew rate at 2.0 A/µs, ideal for driving “Crowbar” SCR’s. The
Undervoltage Indicator Output is an open–collector, NPN
transistor, capable of sinking 30 mA to provide sufficient drive
for LED’s, small relays or shut–down circuitry. These current
capabilities apply to both channels operating simultaneously ,
providing device power dissipation limits are not exceeded.

The MC3425 has an internal 2.5 V bandgap reference
regulator with an accuracy of ± 4.0% for the basic device.

O.V.
Sense

3

U.V.
Sense

4

12.5µA

Note: All voltages and currents are nominal.

+
Comparator

–

Comparator

I

H

Input Section

+

–

Input

O.V.

Input

U.V.

Figure 15. Representative Block Diagram

V

CC

8

200

+

µ

A

200

+

µ

A

52 7

U.V.

O.V.

DLY

DLY

+

+

Output

Comparator
–

O.V.

–
Output
Comparator

U.V.

+

+

2.5V
Reference
Regulator

Gnd

+

Output Section

O.V.

1

6

DRV
U.V.

IND

6

MOTOROLA ANALOG IC DEVICE DATA

MC3425

CROWBAR SCR CONSIDERATIONS

Referring to Figure 16, it can be seen that the crowbar
SCR, when activated, is subject to a large current surge from
the output capacitance, C

. This capacitance consists of

out

the power supply output capacitors, the load’s decoupling
capacitors, and in the case of Figure 16A, the supply’s input
filter capacitors. This surge current is illustrated in Figure 17,
and can cause SCR failure or degradation by any one of
three mechanisms: di/dt, absolute peak surge, or I2t. The
interrelationship of these failure methods and the breadth of
the applications make specification of the SCR by the
semiconductor manufacturer difficult and expensive.
Therefore, the designer must empirically determine the SCR
and circuit elements which result in reliable and effective OVP
operation. However, an understanding of the factors which
influence the SCR’s di/dt and surge capabilities simplifies
this task.

1. di/dt

As the gate region of the SCR is driven on, its area of
conduction takes a finite amount of time to grow, starting as a
very small region and gradually spreading. Since the anode

Figure 16. Typical Crowbar Circuit Configurations

current flows through this turned–on gate region, very high
current densities can occur in the gate region if high anode
currents appear quickly (di/dt). This can result in immediate
destruction of the SCR or gradual degradation of its forward
blocking voltage capabilities – depending on the severity of
the occasion.

The value of di/dt that an SCR can safely handle is
influenced by its construction and the characteristics of the
gate drive signal. A center–gate–fire SCR has more di/dt
capability than a corner–gate–fire type, and heavily
overdriving ( 3 to 5 times IGT) the SCR gate with a fast < 1.0
µs rise time signal will maximize its di/dt capability. A typical
maximum number in phase control SCRs of less than 50
A(RMS) rating might be 200 A/µs, assuming a gate current of
five times IGT and < 1.0 µs rise time. If having done this, a di/dt
problem is seen to still exist, the designer can also decrease
the di/dt of the current waveform by adding inductance in
series with the SCR, as shown in Figure 18. Of course, this
reduces the circuit’s ability to rapidly reduce the dc bus
voltage and a tradeoff must be made between speedy
voltage reduction and di/dt.

(A) SCR Across Input of Regulator

V

in

(B) SCR Across Output of Regulator

V

in

Series

Regulator

++

C

in

Regulator

++

C

in

*Needed if supply is not current limited.

Series

C

out

C

out

MC3425

*

MC3425

V

out

V

out

MOTOROLA ANALOG IC DEVICE DATA

7

MC3425

Figure 17. Crowbar SCR Surge Current Waveform

l

di
dt

2. Surge Current

If the peak current and/or the duration of the surge is
excessive, immediate destruction due to device overheating
will result. The surge capability of the SCR is directly
proportional to its die area. If the surge current cannot be
reduced (by adding series resistance – see Figure 18) to a
safe level which is consistent with the system’s requirements
for speedy bus voltage reduction, the designer must use a
higher current SCR. This may result in the average current
capability of the SCR exceeding the steady state current
requirements imposed by the DC power supply.

l

pk

Surge Due to
Output Capacitor

Current Limited
Supply Output

t

A WORD ABOUT FUSING

Before leaving the subject of the crowbar SCR, a few
words about fuse protection are in order. Referring back to
Figure 16A, it will be seen that a fuse is necessary if the
power supply to be protected is not output current limited.
This fuse is not meant to prevent SCR failure but rather to
prevent a fire!

In order to protect the SCR, the fuse would have to
possess an I2t rating less than that of the SCR and yet have
a high enough continuous current rating to survive normal
supply output currents. In addition, it must be capable of
successfully clearing the high short circuit currents from the
supply. Such a fuse as this is quite expensive, and may not
even be available.

The usual design compromise then is to use a garden
variety fuse (3AG or 3AB style) which cannot be relied on to
blow before the thyristor does, and trust that if the SCR does
fail, it will fail short circuit. In the majority of the designs, this
will be the case, though this is difficult to guarantee. Of
course, a sufficiently high surge will cause an open. These
comments also apply to the fuse in Figure 16B.

CROWBAR SCR SELECTION GUIDE

As an aid in selecting an SCR for crowbar use, the
following selection guide is presented.

Figure 18. Circuit Elements Affecting

SCR Surge & di/dt

R

LeadLLead

ESR

Output

ESL

R & L EMPIRICALLY DETERMINED!

Cap

To

MC3423

R

L

UNDERVOLTAGE SENSING

An undervoltage sense circuit with hysteresis may be
designed, as shown in Figure 11, using the following
equations:

V

*

12.5mA

2.5 R1

CC1

*

V

CC1

2.5

where: V

R2

+

+

CCU

V

R1

is the designed upper trip point

CCU

(output indicator goes off)
V

is the lower trip point

CC1

(output indicator goes on)

Device I

MCR310 Series 10 A 100 A
MCR16 Series 16 A 150 A
MCR25 Series 25 A 300 A
2N6501 Series 25 A 300 A
MCR69 Series 25 A 750 A
MCR264 Series 40 A 400 A
MCR265 Series 55 A 550 A

RMS

I

TSM

8

MOTOROLA ANALOG IC DEVICE DATA

NOTE 2

–T–

SEATING
PLANE

H

58

–B–

14

F

–A–

C

N

D

K

G

0.13 (0.005) B

M

T

MC3425

OUTLINE DIMENSIONS

P1 SUFFIX

PLASTIC PACKAGE

CASE 626–05

ISSUE K

L

J

M

M

A

M

NOTES:

1. DIMENSION L TO CENTER OF LEAD WHEN
FORMED PARALLEL.

2. PACKAGE CONTOUR OPTIONAL (ROUND OR
SQUARE CORNERS).

3. DIMENSIONING AND TOLERANCING PER ANSI
Y14.5M, 1982.

DIM MIN MAX MIN MAX

A 9.40 10.16 0.370 0.400
B 6.10 6.60 0.240 0.260
C 3.94 4.45 0.155 0.175
D 0.38 0.51 0.015 0.020
F 1.02 1.78 0.040 0.070
G 2.54 BSC 0.100 BSC
H 0.76 1.27 0.030 0.050
J 0.20 0.30 0.008 0.012
K 2.92 3.43 0.115 0.135
L 7.62 BSC 0.300 BSC
M ––– 10 ––– 10
N 0.76 1.01 0.030 0.040

INCHESMILLIMETERS

__

MOTOROLA ANALOG IC DEVICE DATA

9

MC3425

NOTES

10

MOTOROLA ANALOG IC DEVICE DATA

MC3425

NOTES

MOTOROLA ANALOG IC DEVICE DATA

11

MC3425

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the suitability of its products for any particular purpose, nor does Motorola assume any liability arising out of the application or use of any product or circuit, and
specifically disclaims any and all liability, including without limitation consequential or incidental damages. “T ypical” parameters which may be provided in Motorola
data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All operating parameters, including “Typicals”
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USA/EUROPE / Locations Not Listed: Motorola Literature Distribution; JAPAN: Nippon Motorola Ltd.; Tatsumi–SPD–JLDC, 6F Seibu–Butsuryu–Center,

P.O. Box 20912; Phoenix, Arizona 85036. 1–800–441–2447 or 602–303–5454 3–14–2 Tatsumi Koto–Ku, Tokyo 135, Japan. 03–81–3521–8315

MFAX: RMF [e-mail] – TOUCHT ONE 602–244–6609 ASIA/PACIFIC: Motorola Semiconductors H.K. Ltd.; 8B Ta i Ping Industrial Park,
INTERNET: http://Design–NET.com 51 Ting Kok Road, Tai Po, N.T., Hong Kong. 852–26629298

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MOTOROLA ANALOG IC DEVICE DATA

M3425/D

*MC3425/D*