ST VIPER28 User Manual

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Features

VIPER28

Off-line high voltage converters

■ 800 V avalanche rugged power section

■ PWM operation with frequency jittering for low

EMI

■ Operating frequency:

– 60 kHz for L type
– 115 kHz for H type

■ Standby power < 50 mW at 265 Vac

■ Limiting current with adjustable set point

■ Adjustable and accurate over-voltage

protection

■ On-board soft-start

■ Safe auto-restart after a fault condition

■ Hysteretic thermal shutdown

■ Delayed overload protection

Application

■ Auxiliary power supply for consumer and home

equipment

■ ATX auxiliary power supply

■ Low / medium power AC-DC adapters

■ SMPS for set-top boxes, DVD players and

recorders, white goods

DIP-7DIP-7

Description

The device is an off-line converter with an 800 V
rugged power section, a PWM control, two levels
of over-current protection, over-voltage and
overload protections, hysteretic thermal
protection, soft-start and safe auto-restart after
any fault condition removal. Burst mode operation
and device very low consumption helps to meet
the standby energy saving regulations. Advance
frequency jittering reduces EMI filter cost. The
extra power timer allows the management of
output peak power for a designed time window.

The high voltage start-up circuit is embedded in
the device.

Figure 1. Typical topology

+

DC input high voltage
wide range

-

DRAIN

DRAIN

VIPER28

VDD

GND

CONT

EPT

FB

+

DC Output voltage

-

Table 1. Device summary

Order codes Package Packaging

VIPER28LN

DIP-7 Tube

VIPER28HN

September 2008 Rev 1 1/29

www.st.com

29

Contents VIPER28

Contents

1 Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2 Typical power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

3 Pin settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

3.1 Connection diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

3.2 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

4 Electrical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

4.1 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

4.2 Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

4.3 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

5 Typical electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

6 Typical circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

7 Operation descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

7.1 Power section and gate driver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

7.2 High voltage startup generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

7.3 Power-up and soft-start up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

7.4 Power down operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

7.5 Auto restart operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

7.6 Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

7.7 Current mode conversion with adjustable current limit set point . . . . . . . 19

7.8 Over-voltage protection (OVP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

7.9 About CONT pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

7.10 Feed-back and overload protection (OLP) . . . . . . . . . . . . . . . . . . . . . . . . 21

7.11 Burst-mode operation at no load or very light load . . . . . . . . . . . . . . . . . . 24

7.12 Extra power management function (EPT) . . . . . . . . . . . . . . . . . . . . . . . . 24

7.13 2nd level over-current protection and hiccup mode . . . . . . . . . . . . . . . . . 25

2/29

VIPER28 Contents

8 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

9 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

3/29

Block diagram VIPER28

1 Block diagram

Figure 2. Block diagram

EPT

CONT

CONT

Tovl

Tovl

LEB

LEB

EPT

Tov l

Tov l

BLOCK

BLOCK

SOFT

SOFT

START

START

OVP DETECTION

OVP DETECTION

LOGIC

LOGIC

OVP

OVP

OLP

OLP

OCP

OCP

BLOCK

BLOCK

PWM

PWM

BLOCK

BLOCK

BURST-MODE

BURST-MODE
REFERENCES

REFERENCES

OSCI LLATOR

OSCI LLATOR

-

-

OCP

OCP

+

+

PWM

PWM

+

+

-

-

+

+

-

­Disable

Disable

BURST-MODE

BURST-MODE

LOGIC

LOGIC

BURST

BURST

Vcc

VDD

Internal Supply bus

Internal Supply bus

&

&

Ref erence Voltag es

Ref erence Voltag es

TURN-ON

TURN-ON

2nd OCP

2nd OCP

-

-

+

+

BURST

BURST

LOGIC

LOGIC

LEB

LEB

2nd OCP

2nd OCP

LOGIC

LOGIC

SUPPLY

SUPPLY

& UVLO

& UVLO

S

S

R

R

UVLO

UVLO

Q

Q

OTP OVP OLP

OTP OVP OLP

HV_ON Ist art-up

HV_ON Ist art-up

TH ER MAL

TH ER MAL

SHUTD OWN

SHUTD OWN

OTP

OTP

HV_ON

HV_ON

SRQ

SRQ

Rsense

Rsense

DRAIN

DRAIN

FB

FB

2 Typical power

Table 2. Typical power

Part number

1. Typical continuous power in non ventilated enclosed adapter measured at 50 °C ambient.

2. Maximum practical continuous power in an open frame design at 50

Adapter

(1)

230 V

AC

Open frame

(2)

Adapter

85-265 V

(1)

VIPER28 18 W 24 W 10 W 13 W

°C ambient, with adequate heat sinking.

GND

GND

AC

Open frame

(2)

4/29

VIPER28 Pin settings

3 Pin settings

3.1 Connection diagram

Figure 3. Connection diagram (top view)

3.2 Pin description

Table 3. Pin description

N. Name Function

1 GND This pin represents the device ground and the source of the power section.

2VDD

3CONT

4FB

5 EPT

7,8 DRAIN

Supply voltage of the control section. This pin also provides the charging
current of the external capacitor during start-up time.

Control pin. The following functions can be selected:

1. current limit set point adjustment. The internal set default value of the cycle­by-cycle current limit can be reduced by connecting to ground an external
resistor.

2. output voltage monitoring. A voltage exceeding 3 V shuts the IC down
reducing the device consumption. This function is strobed and digitally filtered
for high noise immunity.

Control input for duty cycle control. Internal current generator provides bias
current for loop regulation. A voltage below 0.6 V activates the burst-mode
operation. A level close to 3.3 V means that the device is approaching the

cycle-by-cycle over-current set point.

This pin allows the connection of an external capacitor for the extra power
management. If the function is not used, the pin has to be connected to GND.

High voltage drain pin. The built-in high voltage switched start-up bias current is
drawn from this pin too.

GND

VDD

CONT

FB

DRAIN

DRAIN

EPT

BR

5/29

Electrical data VIPER28

4 Electrical data

4.1 Maximum ratings

Table 4. Absolute maximum ratings

Symbol Pin Parameter Value Unit

V

DRAIN

E

I

AR

I

DRAIN

V

CONT

V

V

EPT

V

I

DD

P

TOT

T

T

STG

AV

FB

DD

J

7, 8 Drain-to-source (ground) voltage 800 V

7, 8 Repetitive avalanche energy (limited by TJ = 150 °C) 5 mJ

7, 8 Repetitive avalanche current (limited by TJ = 150 °C) 1.5 A

7, 8 Pulse drain current 3 A

3 Control input pin voltage (with I

4 Feed-back voltage -0.3 to 5.5 V

5 EPT input pin voltage 5 V

2 Supply voltage (IDD = 25 mA) Self limited V

2 Input current 25 mA

4.2 Thermal data

Table 5. Thermal data

Symbol Parameter Max value Unit

= 1 mA) Self limited V

CONT

Power dissipation at TA < 50 °C 1 W

Operating junction temperature range -40 to 150 °C

Storage temperature -55 to 150 °C

R

R

1. When mounted on a standard single side FR4 board with 100 mm2 (0.155 sq in) of Cu (35 m thick)

Thermal resistance junction pin 25 °C/W

thJP

Thermal resistance junction ambient 75

thJA

6/29

(1)

°C/W

VIPER28 Electrical data

4.3 Electrical characteristics

(TJ = -25 to 125 °C, VDD = 14 V; unless otherwise specified)

Table 6. Power section

Symbol Parameter Test condition Min Typ Max Unit

I

= 1 mA, VFB = GND

V

BVDSS

I

OFF

R

DS(on)

C

OSS

Table 7. Supply section

Break-down voltage

OFF state drain current

Drain-source on state
resistance

Effective (energy related)
output capacitance

Symbol Parameter Test condition Min Typ Max Unit

DRAIN

TJ = 25 °C

V

V

I
V

I
V

V

= max rating,

DRAIN

= GND

FB

= 0.4 A, VFB = 3 V,

DRAIN

= GND, TJ = 25 °C

EPT

= 0.4 A, VFB = 3 V,

DRAIN

= GND, TJ = 125 °C

EPT

= 0 to 640 V 40 pF

DRAIN

800 V

60 μA

7 Ω

14 Ω

Volt ag e

V

DRAIN

I

DDch

V

DD

V

DDclamp

V

DDon

V

DDoff

V

DD(RESTART)

Current

I

DD0

I

DD1

I

DD_FAULT

I

DD_OFF

Drain-source start voltage 60 80 100 V

_START

Start up charging current

V

V
V

V

V

= 120 V,

DRAIN

= GND, VFB = GND,

EPT

= 4 V

DD

= 120 V,

DRAIN

= GND, VFB = GND,

EPT

-2 -3 -4 mA

-0.4 -0.6 -0.8 mA

VDD = 4 V after fault.

Operating voltage range After turn-on 8.5 23.5 V

VDD clamp voltage IDD = 20 mA 23.5 V

VDD start up threshold

VDD under voltage
shutdown threshold

VDD restart voltage
threshold

Operating supply current,
not switching

Operating supply current,
switching

V

V

V

V

= 120 V,

DRAIN

= GND, VFB = GND

EPT

= 120 V,

DRAIN

= GND, VFB = GND

EPT

VFB = GND, FSW = 0 k H z ,
V

= GND, VDD = 10 V

EPT

V

DRAIN

= 120 V,

FSW = 60 kHz

V

DRAIN

= 120 V,

13 14 15 V

7.588.5V

44.55 V

FSW = 115 kHz

Operating supply current,
with protection tripping

Operating supply current
with VDD < V

DD_OFF

VDD = 7 V 270 uA

0.9 mA

2.5 mA

3.5 mA

400 uA

7/29

Electrical data VIPER28

Table 8. Controller section

(T

= -25 to 125 °C, V

J

Symbol Parameter Test condition Min Typ Max Unit

Feed-back pin

= 14 V; unless otherwise specified)

DD

V

FBolp

V

FBlin

V

FBbm

V

FBbmhys

Over-load shut down
threshold

Linear dynamics upper limit 3.2 3.5 3.7 V

Burst mode threshold Voltage falling 0.6 V

Burst mode hysteresis Voltage rising 100 mV

4.7 4.8 5.2 V

VFB = 0.3 V -150 -200 -280 uA

I

R

FB(DYN)

H

FB

FB

Feed-back sourced current

Dynamic resistance V

ΔVFB / ΔI

D

3.3 V < V

FB

< 4.8 V -3 uA

FB

< 3.3 V 14 20 kΩ

26V/A

CONT pin

VCONT_l Low level clamp voltage I

= -100 uA 0.5 V

CONT

Current limitation

VFB = 4 V,

I

Dlim

Max drain current limitation

I

CONT

= -10 µA

0.75 0.80 0.85 A

TJ = 25 °C

t

SS

T

ON_MIN

Soft-start time 8.5 ms

Minimum turn ON time 220 400 480 ns

td Propagation delay 100 ns

t

LEB

I

D_BM

Leading edge blanking 300 ns

Peak drain current during
burst mode

Oscillator section

VIPER28LV

F

OSC

FD Modulation depth

FM Modulation frequency 250 Hz

D

MAX

8/29

VIPER28H 103 115 127 kHz

Maximum duty cycle 70 80 %

V

= 0.6 V 160 mA

FB

= operating

DD

54 60 66 kHz
voltage range,
VFB = 1 V

VIPER28L±4kHz

VIPER28H ±8 kHz

VIPER28 Electrical data

Table 8. Controller section (continued)

(T

= -25 to 125 °C, V

J

Symbol Parameter Test condition Min Typ Max Unit

= 14 V; unless otherwise specified)

DD

Over-current protection (2

I

DMAX

Second over-current
threshold

Over-voltage protection

V

OVP

T

STROBE

Over-voltage protection
threshold

Over-voltage protection
strobe time

Extra power management

I

DLIM_EPT

V

EPT(STOP)

V

EPT(RESTART)

I

EPT

Drain current limit with
EPT function

EPT shut down threshold

EPT restart threshold 0.6 V

Sourced EPT current 5 μA

Thermal shutdown

T

T

HYST

SD

Thermal shutdown
temperature

Thermal shutdown
hysteresis

nd

OCP)

I

CONT

T

I

CONT

< -10 μA

= 25 °C

J

< -10 μA

1.2 A

2.733.3V

2.2 us

85%

IDLIM

A

4V

150 170 °C

30 °C

9/29