SGS Thomson Microelectronics VB408FI, VB408 Datasheet

VB408



HIGH VOLTAGE LINEAR REGULATOR

TYPE

VB408
VB408FI
VB408B

■ INPUT VOLTAGEUP TO 400 V DC OR 285 V

RMS RECTIFIED

■ OUTPUTVOLTAGEADJUSTABLEFROM1.25

TO VIN-30V

■ OUTPUT CURRENT LIMITED TO 40 mA

■ THERMAL SHUT-DOWN PROTECTION

■ SHORT CIRCUIT PROTECTION

DESCRIPTION

The VB408, VB408B, VB408FI are fully protected
positive adjustable voltage regulators made using a
proprietary High Voltage VIPower technology. The
device can beconnected toa D.C. source (upto 400V) or
in off-line application directly to the rectified main (110V/
230V). It is particularly suitable to be used in the
manufacture of DC/DC converters, AC/DC converters,

∆V

IN,OUT

I

LIM

400 V 40 mA 1.25 to V

V

OUT

IN

-30 V

/ VB408B / VB408FI

POWER I.C.

PRELIMINARY DATA

3

2

1

TO-220

ISOWATT220

3

1

D2PAK

ORDER CODES :

TO-220

VB408

ISOWATT220 VB408FI

D2PAK

start-up circuits, pneumatic valve drivers and current
sources. The device is able to drive resistive or inductive
loads with an output voltage from 1.25V to V
providing an internally limited output current; it has built in
short circuit and thermal shutdown protections. The
device does not provide galvanic insulation from main.

VB408B

1

3

2

IN-30V

BLOCK DIAGRAM

+
_

CURRENT

SENSE

REF 2

REF 1

IN

V

Power
Stage

Current
Limitation

+
_

Thermal
Protection

Control
Signal

ADJ

REF 3

BIAS

CIRCUIT

+

_

September 1999 1/8

VOUT

FC00410

1

ABSOLUTE MAXIMUM RATING

Symbol Parameter

V

∆

IN,OUT

I

OUT

V

ESD

P

T

T

STG

Input to Output Voltage at 20 mA - 0.2 to 420 V
Output current Internally limited mA
Electrostatic discharge (R=1.5kΩ, C=100pF) 2000 V
Power dissipation at TC=25oC893189W

tot

Junction operating temperature - 40 to150 °C

j

Storage temperature - 55 to 150 °C

THERMAL DATA

Symbol Parameter

R

thj-case

R

thj-amb

(*) When mounted using the minimum recommended pad size on FR-4 board (1 inch2)

Thermal resistance junction-case (MAX) 1.4 4 1.4 °C/W
Thermal resistance junction-ambient (MAX) 60 60 35 (*) °C/W

CONNECTION DIAGRAM (TOP VIEW)

VB408 / VB408B / VB408FI

Value

TO-220 ISOWATT220 D2PAK

Value

TO-220 ISOWATT220 D2PAK

Unit

Unit

3
2

1

V

OUT

V

IN

ADJ

3

V

2

1

OUT

V

IN

ADJ

TO-220 / ISOWATT220 D2PAK

ELECTRICAL CHARACTERISTICS (VIN=300VDC; -25°C<Tj<125°C; I

specified)

LOAD

=15mA; V

=0V unless otherwise

ADJ

Symbol Parameter Test Conditions Min Typ Max Unit

Input Voltage 30 400 V
Input to Output Voltage 30 V
Output Reference Voltage V
Line Regulation V

IN

Load Regulation V

LOAD

=0V 1.20 1.24 1.28 V

ADJ

=0V; VIN=30 to 400 VDC 100 µV/V

ADJ
ADJ

=0V; I

=1 to 20 mA 6 mV/mA

LOAD

Adjustment Pin Current 50 70 90 µA
Minimum Load Current 1.2 mA
Output Current Limit 40 60 mA
Junction Temperature

Shutdown Limit
Junction Temperature

Shutdown Hysteresis

135 150 °C

25 °C

∆V

∆V

V

V

IN-VOUT

V

REF

OUT

/∆I

OUT

I

ADJ

I

BIAS

I

LIM

T

jsh

∆T

IN

/∆V

jsh

2/8

1

VB408 / VB408B / VB408FI

Figure 1: Typical application diagram

VIN

C1

VOUTVIN

VB408

A

DJ

VREF

R1

R2

V

OUT

C2

FC00420

OPERATION DESCRIPTION

The VB408, VB408B, VB408FI are positive voltage
regulators continuously adjustable from 1.25V to the input
voltage minus a dropout of 30V through an external
divider. In order to set the proper internal reference
voltage, a typical 70µA current has to be drawn from the
ADJ pin. Considering that, it results:

V

OUT =VREF

To simplify this formula, neglecting I
the term

V

REF/R1

R1must be chosen so toobtain a minimum 1.2mA current
flowing through the divider. In such a way the V
will be affected by an error <5%. The current set resistor
R

should be tied directly to the output terminal of the

1

regulator rather than near the load. This eliminates line
drops from appearing in series with the reference and
degrading regulation. The output voltage can also be set
by a zener diode put between the adjustment pin and
ground (Figure 2). The biasing current of the zener is
properly chosen by R
the ripple rejection and reduces the value of the worst
case output voltage error. In this case the output voltage
is given by:

V

OUT=VREF+VZ

In order to reduce excessive output ringing, a minimum
output capacitor C
will improve loop stability and output impedance. The
VB408/VB408B/VB408FI can be connected both to a DC
source or to a 285V r.m.s. line by a rectifier diode that
prevents a negative voltage to beapplied to thedevice. In
the first case the input capacitor C
whereas in the second case a high value of C
must be chosen. In fact, in this kind of application, C
to supply to the input pin the minimum allowed voltage

(1+R2/R1)+I

2

ADJR2

ADJ

resistor. The zener diode improves

1

of 0.1µF is suggested. This capacitor

1

with respect to

value

OUT

is not needed,

(> 1µF)

1

has

1

during the negative half wave. Obviously bigger C
more constant the input voltage is and consequently
smaller the output voltage ripple. For the right choice of
the input capacitor, you have also to remember that
increasing its value you will obtain an increased power
dissipation, and a heatsink could be required. The right
heatsink is determined by the load current, input voltage
and ambient temperature. In case of pulse or A.C.
operation the junction temperature is limited by the
thermal capacitances since the package and the heatsink
masses are able to absorb heat. If the junction
temperature reaches the thermal shutdown limit the
output stage of the regulator is turned-off so that only the
biasing current of the device can flow into the input pin.
Thermal hysteresis is added just to prevent oscillations.
The device is able to provide minimum 40 mA for a time
that is function of dissipated power and consequently of
the usedheatsink. In general the device is also suitable in
electronically switched motor housekeeping supply,
consumer equipments controls power supply or constant
current source.

APPLICATION EXAMPLE

The most common application for the device is in the DC/
DC converters with an input voltage up to 400 VDC and a
C

suggested value of 0,1µF.

2

Using an external rectifier an AC/DC converter can be
easily implemented, in this case the device can operate
with an AC voltage up to 285VRMS. In this case must be
used a minimum 1µF input capacitor to provide the load
current during the negative half cycle of the main. Another
important circuit that can be implemented is the start up
function for low voltage input PWM ICs directly from a
high voltage source (see figure 3).

value,

1

3/8

1