SI9121DY-3-T1 VISHAY [Vishay Siliconix], SI9121DY-3-T1 Datasheet

SI9121DY-3-T1

Manufacturer Part Number

SI9121DY-3-T1

Description

High-Voltage, Non-Isolated Buck-Boost Converter for ISDN Digital Phones

Manufacturer

VISHAY [Vishay Siliconix]

Datasheet

1.SI9121DY-3-T1.pdf (9 pages)

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DESCRIPTION

The Si9121 simplifies the −48-V to +5-V or +3.3-V converter

design for ISDN application by integrating the floating

feedback error amplifier providing direct output voltage

regulation. This approach eliminates the need for an external

shunt regulator. The Si9121 also integrates a high voltage

depletion mode MOSFET which allows the converter to be

powered directly from the high input bus voltage without

requiring an external start-up circuit. Combined with simple

magnetic design due to its non-isolated topology, the Si9121

provides a one-chip solution for complete ISDN power supply.

Document Number: 71112

S-40708—Rev. C, 19-Apr-04

−48 V

FEATURES

D Fixed +5-V or +3.3-V Output

D Integrated Floating Feedback Amplifier

D On-Chip 70-V, 1.5-W N-Channel

D Integrated High Voltage Start-Up Circuit,

FUNCTIONAL BLOCK DIAGRAM

NEG

MOSFET Switch

with V

Regulator

High-Voltage, Non-Isolated Buck-Boost Converter

BYPASS

COMP

for ISDN Digital Phones

NEG

Reference Generator

Control

D −10-V to −60-V Input Voltage Range

D 95-kHz PWM Operation

D Integrated Soft-Start and Oscillator

D High Efficiency Over Full Load Range

D Under Voltage Lockout

Regulator

GND

In order to reduce external component count, the Si9121 has

a fully integrated 95-kHz oscillator and soft-start circuit.

The Si9121 is available in both standard and lead (Pb)-free

SOIC-8 pin packages, and is offered in either +5-V or +3.3-V

fixed

respectively).

temperature requirements in many applications, the Si9121 is

rated to the industrial temperature range of −40_C to 85_C.

output

OUT

In order to satisfy the stringent ambient

options

D Current Mode Control

D Hiccup Mode Short Circuit

D Thermal Shutdown

D SOIC-8 Narrow-Body Package

(Si9121DY-5

Protection

Vishay Siliconix

+5 V/400 mA

+3.3 V/400 mA

Si9121

www.vishay.com

Si9121DY-3,

OUT

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SI9121DY-3-T1 Summary of contents

Page 1

... GND V Regulator CC Reference Generator V OUT L X Control V C NEG S Si9121 Vishay Siliconix D Current Mode Control D Hiccup Mode Short Circuit Protection D Thermal Shutdown D SOIC-8 Narrow-Body Package options (Si9121DY-5 or Si9121DY-3, In order to satisfy the stringent ambient V OUT +5 V/400 mA or +3.3 V/400 mA www.vishay.com 1 ...

Page 2

Si9121 Vishay Siliconix ABSOLUTE MAXIMUM RATINGS (ALL VOLTAGES REFERENCED TO GND = ...

Page 3

SPECIFICATIONS (All Voltages Are With Respect To V Parameter Symbol Supply Supply Current I GND (Internally Regulater) Supply Current I CC (External V Applied supply Current I OUT OUT Start-Up Current I START Thermal Shutdown Thermal Shutdown ...

Page 4

Si9121 Vishay Siliconix TYPICAL CHARACTERISTICS (INTERNALLY REGULATED, 25_C UNLESS NOTED) 5-V V vs. Temperature OUT 5.15 5.10 5.05 5.00 4.95 4.90 4.85 −40 − Temperature (_C) r vs. Temperature DS(on) 2.5 2.0 1.5 1.0 0.5 −40 −20 ...

Page 5

... I (mA) OUT Document Number: 71112 S-40708—Rev. C, 19-Apr-04 Output Load vs. Efficiency (Si9121DY- 1000 Output Load vs. Efficiency (Si9121DY- 1000 Si9121 Vishay Siliconix No V Winding 100 ...

Page 6

... The soft-start circuit is enable once the V www.vishay.com 6 Part Number Si9121DY-5- Si9121DY-5-T1— Si9121DY-3-T1 GND 6 Si9121DY-3-T1— OUT Si9121DY-5 Si9121DY-3 Eval Kit Si9121DB-5 Si9121DB-3 Function the UVLO threshold. compensation components (see Typical Application Circuit) the soft-start time is approximately 10 ms. Oscillator voltage ...

Page 7

DETAILED DESCRIPTION Bypass The bypass voltage of the Si9121 is set at a particular positive reference relative to the V pin. The bypass voltage is used NEG to set an accurate voltage and bias current for the on-chip oscillator and ...

Page 8

... C5 0.1 mF Si9121DY-5 C4 180 (27 kW for Si9121DY-3) GND 220 mF 0.1 mF OUT +5 V/400 10MQ100N +3.3 V/400 180 pF (27 kW for Si9121DY *Optional 220 BAS21 D1 10MQ100N ...

Page 9

Specifications of the products displayed herein are subject to change without notice. Vishay Intertechnology, Inc., or anyone on its behalf, assumes no responsibility or liability for any errors or inaccuracies. Information contained herein is intended to provide a product description ...

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