Datasheet

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 2015 Microchip Technology Inc. DS20005399A-page 1

LR8

Features

• 13.2 - 450V input voltage range

• Adjustable 1.20 - 438V output regulation

• 5% output voltage tolerance

• Output current limiting

• 10µA typical ADJ current

• Internal junction temperature limiting

Applications

• Off-line SMPS startup circuits

• Adjustable high voltage constant current source

• Industrial controls

• Motor controls

• Battery chargers

• Power supplies

Description

LR8 is a high-voltage, low-output current, adjustable

linear regulator. This regulator has a wide operating

input voltage range of 13.2 - 450V. The output voltage

can be adjusted from 1.20 - 438V, provided that the

input voltage is at least 12V greater than the output

voltage. The output voltage can be adjusted by means

of two external resistors, R

and R

, as shown in the

typical application circuits. LR8 regulates the voltage

difference between VOUT and ADJ pins to a nominal

value of 1.20V. The 1.20V is amplified by the external

resistor ratio R

and R

. An internal constant bias cur-

rent, of typically 10µA, is connected to the ADJ pin.

This increases V

OUT

by a constant voltage of 10µA

times R2.

LR8 provides both current and temperature limiting.

The output current limit is typically 20mA and the mini-

mum temperature limit is 125°C. An output short-circuit

current will therefore be limited to 20mA. When the

junction temperature reaches its temperature limit, the

output current and/or output voltage will decrease to

prevent the junction temperature from exceeding its

temperature limit. For SMPS start-up circuit applica-

tions, LR8 turns off when an external voltage greater

than the output voltage of the LR8 is applied to VOUT

of the LR8. To maintain stability, a bypass capacitor of

1.0µF or larger and a minimum DC output current of

500µA are required.

LR8 is available in TO-243AA (SOT-89), TO-252 (D-

PAK), and TO-92 packages.

High-Input Voltage, Adjustable, 3-Terminal,

Linear Regulator

Summary of content (16 pages)

PAGE 1
LR8 High-Input Voltage, Adjustable, 3-Terminal, Linear Regulator Features Description • • • • • • LR8 is a high-voltage, low-output current, adjustable linear regulator. This regulator has a wide operating input voltage range of 13.2 - 450V. The output voltage can be adjusted from 1.20 - 438V, provided that the input voltage is at least 12V greater than the output voltage. The output voltage can be adjusted by means of two external resistors, R1 and R2, as shown in the typical application circuits.
PAGE 2
LR8 Package Type VOUT ADJ ADJ VIN VOUT VIN VOUT TO-243AA (SOT-89) TO-92 VOUT ADJ VIN TO-252 See Table 2-1 for pin information Functional Block Diagram VIN Pass Element Overtemp & Overcurrent LR8 DS20005399A-page 2 VOUT 1.2V 10μA ADJ  2015 Microchip Technology Inc.
PAGE 3
LR8 1.0 ELECTRICAL CHARACTERISTICS ABSOLUTE MAXIMUM RATINGS† VIN Input voltage (voltages ref to ADJ).............................................................................................................................. -0.5 to +480V Output voltage range.......................................................................................................................................................... 0.5 to +470V Operating ambient temperature range .............................................
PAGE 4
LR8 2.0 PIN DESCRIPTION The locations of the pins are listed in Package Type. TABLE 2-1: PIN DESCRIPTION Function Description VIN Regulator input. 13.2 - 450V. VOUT Regulator output. ADJ 3.0 Output voltage adjust TYPICAL APPLICATION CIRCUITS . * VIN VIN VOUT VOUT R1 ADJ C1 LR8 C2 RLOAD R2 * Required for conditions where VIN is less than VOUT. FIGURE 3-1: Typical Application Circuit * VIN = 17 to 450V VIN LR8 C1 VOUT = 5.0V VOUT ADJ R1 6.04kΩ 1% R2 18.
PAGE 5
LR8 VIN = (VOUT + 12V) to 450V + VAUXILIARY VOUT1 - VIN LR8 + VOUT VOUT1 ADJ VCC FB FIGURE 3-3: PWM IC SMPS Start-Up Circuit R + VIN LR8 IOUT = 1.20V R VOUT VIN = (VOUT + 12V) to 450V ADJ Load 1.0μF - FIGURE 3-4: High-Voltage, Adjustable, Constant-Current Source  2015 Microchip Technology Inc.
PAGE 6
LR8 Temperature Variation 1.30 LR8 1.20 ADJ 12V 1.25 VOUT = 1.2V 2.4kΩ 1.0μF VOUT (V) VIN 1.15 1.10 1.05 1.00 -50 -25 0 25 50 75 100 125 T (junction) (OC) Adjustment Current 12 11 VOUT = 1.2V VIN 10 ADJ 12V, 200V 400V 2.4kΩ IADJ 1.0ΩF IADJ (µA) LR8 VIN = 400V VIN = 12V 9 8 VIN = 200V 7 6 -50 -25 0 25 50 75 100 125 T (junction) (OC) Load Regulation 5.2 VOUT = 5.0V VIN IOUT LR8 5.1 ADJ 25V 1.0μF RLOAD VOUT (V) 6.04kΩ ±1% 5.0 18.2kΩ ±1% 4.9 4.
PAGE 7
LR8 VOUT vs. VIN 6 VOUT = 5.0V VIN 5 LR8 6.04kΩ ±1% 4 1kΩ 1.0μF 0V to 50V VOUT (V) ADJ 18.2kΩ ±1% 3 2 1 0 0 10 20 30 40 50 8 10 VIN (V) Ripple Rejection VIN 20VP-P @ 60Hz 65V LR8 VOUT = 5.0V ADJ Ripple Regection Ratio (dB) -65 IOUT 6.04kΩ ±1% 1.0μF RLOAD 18.
PAGE 8
LR8 Load Transient Response VIN VOUT = 5.0V LR8 Closed SW 6.04kΩ ±1% ADJ sw 1.0μF 25V Open 10kΩ 18.2kΩ ±1% 532Ω VOUT Load Transient Response Line Transient Response 400V VIN VOUT = 5.0V VIN 400V LR8 0V 6.04kΩ ±1% ADJ VIN 1.0μF 10kΩ 18.2kΩ ±1% 0V VOUT 0V Line Transient Response 400V 400V VIN VIN 0V 0V 5.0V 5.
PAGE 9
LR8 4.0 PACKAGING INFORMATION 4.1 Package Marking Information 3-lead TO-92 Example XXXXXX XXXX e3 YWWNNN LR8 N3 e3 516343 3-lead TO-252 (D-PAK) XXXX XXXXX e3 YYWWNNN Legend: XX...
PAGE 10
LR8 Note: For the most current package drawings, see the Microchip Packaging Specification at www.microchip.com/packaging. DS20005399A-page 10  2015 Microchip Technology Inc.
PAGE 11
LR8 3-Lead TO-243AA (SOT-89) Package Outline (N8) D D1 C E H 1 2 E1 3 L b b1 A e e1 Side View Top View Note: For the most current package drawings, see the Microchip Packaging Specification at www.microchip.com/packaging. Symbol Dimensions (mm) A b b1 C D D1 E E1 MIN 1.40 0.44 0.36 0.35 4.40 1.62 2.29 2.00† NOM - - - - - - - - MAX 1.60 0.56 0.48 0.44 4.60 1.83 2.60 2.29 e 1.50 BSC e1 3.00 BSC H L 3.94 0.73† - - 4.25 1.
PAGE 12
LR8 Note: For the most current package drawings, see the Microchip Packaging Specification at www.microchip.com/packaging. DS20005399A-page 12  2015 Microchip Technology Inc.
PAGE 13
LR8 APPENDIX A: REVISION HISTORY Revision A (June 2015) • Update file to new format  2015 Microchip Technology Inc.
PAGE 14
LR8 PRODUCT IDENTIFICATION SYSTEM To order or obtain information, e.g., on pricing or delivery, refer to the factory or the listed sales office. PART NO.
PAGE 15
LR8 Note the following details of the code protection feature on Microchip devices: • Microchip products meet the specification contained in their particular Microchip Data Sheet. • Microchip believes that its family of products is one of the most secure families of its kind on the market today, when used in the intended manner and under normal conditions. • There are dishonest and possibly illegal methods used to breach the code protection feature.
PAGE 16
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