NTE 7242 Service Manual

NTE7242

Integrated Circuit 12 Watt Low Power

Off Line SMPS Primary Switcher

8−Lead DIP

Description:

The NTE7242 combines a dedicated current mode PWM controller with a high voltage Power MOSFET
on the same silicon chip. Typical applications cover off line power supplies for battery charger adapters,
standby power supplies for TV or monitors, auxiliary supplies for motor control, etc. The internal control
circuit offers the following benefits:

D Large input voltage range on the V

This feature is well adapted to battery charger adapter configurations.

D Automatic burst mode in low load condition.
D Overvoltage protection in hiccup mode.

Features:

D Fixed 60 KHZ Switching Frequency
D 9V to 38V Wide Range V

Voltage

DD

D Current Mode Control
D Auxiliary Undervoltage Lockout with Hysteresis
D High Voltage Start Up Current Source
D Overtemperature, Overcurrent and Overvoltage Protection with Autorestart

pin accommodates changes in auxiliary supply voltage.

DD

Absolute Maximum Ratings:

Supply Voltage, V
Switching Drain Source Voltage (T
Start Up Drain Source Voltage (T
Continuous Drain Current, I
Feedback Current, I
Operating Junction Temperature Range, T
Case Operating Temperature Range, T
Storage Temperature Range, T
Thermal Resistance, Junction−to−Case, R

DD

FB

= +25 to +125°C, Note 1), V

J

= +25 to +125°C, Note 2), V

J

D

J

C

stg

thJC

Thermal Resistance, Junction−to−Ambient (Note 3), R
Electrostatic Discharge, V

Machine Model (R=0W; C=200pF)

(ESD

)

thJA

DS(sw)

DS(st)

−0.3 to 730V............

−0.3 to 400V..............

Internally limited.............................................

Internally limited.................................

−40 to +150°C....................................

−55 to +150°C..........................................

50V................................................................

3mA.............................................................

+15°C/W....................................

+45°C/W..........................

200V............................................

Charged Device Model 1.5kV......................................................

Note 1. This parameter applies when the start up current source is off. This is the case when the V

voltage has reached V

and remains above V

DDon

DDoff

.

Note 2. This parameter applies when the start up current source is on. This is the case when the V

voltage has not yet reached V

Note 3. When mounted on a standard single−sided FR4 board with 200mm

or has fallen below V

DDon

DDoff

.

2

of Cu (at least 35mm thick)

connected to all DRAIN pins.

DD

DD

Electrical Characteristics: (TJ=+25°C, VDD=18V, unless otherwise specified)

Parameter Symbol Test Conditions Min Typ Max Unit

Power

Drain−Source Voltage BV

Off State Drain Current I

Static Drain−Source On State

R

Resistance

Fall Time t

Rise Time t

Drain Capacitance C

Supply

Start Up Charging Current I

Start Up Charging Current in Thermal

DDch

I

DDoff

Shutdown

Operating Supply Current Not Switching I

Operating Supply Current Switching I

Restart Duty Cycle D

VDD Undervoltage Shutdown Threshold V

VDD Start Up Threshold V

VDD Threshold Hysteresis V

VDD Overvoltage Hysteresis V

DDhyst

DDovp

Oscillator

DSSID

DSS

DSonID

VDS=500V, VFB=2V, TJ=+125°C − − 0.1 mA

ID=0.2A, VIN=300V, Note 4 − 100 − ns

f

ID=0.4A, VIN=300V, Note 4 − 50 − ns

r

VDS=25V − 40 − pF

oss

VDS=100V, VDD=0V to V

VDD=5V, VDS=100V, TJ > TSD − T

DD0

DD1

RST

DDoff

DDon

IFB=2mA − 3 5 mA

IFB=0.5mA, ID=50mA, Note 5 − 4.5 − mA

=1mA, VFB=2V 730 − − V

=0.4A − 15 17

TJ=+100°C − − 31

DDon

HYST

− −1 − mA

0 − − mA

W

W

− 16 − %

7 8 9 V

13 14.5 16 V

5.8 6.5 7.2 V

38 42 46 V

Oscillator Frequency Total Variation F

OSC

VDD=V

to 35V, TJ=0 to +100°C 54 60 66 kHz

DDoff

PWM Comparator

IFB to ID Current Gain G

Peak Current Limitation I

IFB Shutdown Current I

FB Pin Input Impedance R

Current Sense Delay to Turn−Off t

Blanking Time t

Minimum Turn On Time t

ONmin

ID

Dlim

FBsd

FB

d

b

VFB=0V 0.56 0.7 0.84 A

ID=0mA

ID=0.4A − 200 − ns

− 560 − −

− 0.9 − mA

− 1.2 −

kW

− 500 − ns

− 700 − ns

Overtemperature

Thermal Shutdown Temperature T

Thermal Shutdown Hysteresis T

SD

HYST

140 170

− 40

°C

−

°C

−

Note 4. On clamped inductive load.
Note 5. These test conditions obtained with a resistive load are leading to the maximum conduction

time of the device.