lt3085ems8e Linear Technology Corporation, lt3085ems8e Datasheet

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lt3085ems8e

Manufacturer Part Number
lt3085ems8e
Description
Adjustable 500ma Single Resistor Low Dropout Regulator
Manufacturer
Linear Technology Corporation
Datasheet

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FEATURES
APPLICATIONS
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TYPICAL APPLICATION
Outputs May be Paralleled for Higher Current and
Heat Spreading
Output Current: 500mA
Single Resistor Programs Output Voltage
1% Initial Accuracy of SET Pin Current
Output Adjustable to 0V
Current Limit Constant with Temperature
Low Output Noise: 40μV
Wide Input Voltage Range: 1.2V to 36V
Low Dropout Voltage: 300mV
< 1mV Load Regulation
< 0.001%/ V Line Regulation
Minimum Load Current: 0.5mA
Stable with Minimum 2.2μF Ceramic Capacitor
Current Limit with Foldback and Overtemperature
Protected
8-Lead MSOP, and 6-Lead 2mm × 3mm DFN Packages
High Current All Surface Mount Supply
High Effi ciency Linear Regulator
Post Regulator for Switching Supplies
Low Parts Count Variable Voltage Supply
Low Output Voltage Power Supplies
1.2V TO 36V
V
Variable Output Voltage 500mA Supply
IN
V
CONTROL
1μF
IN
SET
RMS
R
V
SET
OUT
LT3085
+
= R
(10Hz to 100kHz)
SET
• 10μA
3085 TA01a
OUT
V
2.2μF
OUT
DESCRIPTION
The LT
can be paralleled to increase output current or spread
heat on surface mounted boards. Designed as a precision
current source and voltage follower, this new regulator
fi nds use in many applications requiring high current,
adjustability to zero, and no heat sink. The device also
brings out the collector of the pass transistor to allow
low dropout operation—down to 300mV—when used
with a second supply.
A key feature of the LT3085 is the capability to supply a
wide output voltage range. By using a reference current
through a single resistor, the output voltage is programmed
to any level between zero and 36V. The LT3085 is stable
with 2.2μF of capacitance on the output, and the IC uses
small ceramic capacitors that do not require additional
ESR as is common with other regulators.
Internal protection circuitry includes current limiting
and thermal limiting. The LT3085 is offered in the 8-lead
MSOP and a low profi le (0.75mm) 6-lead 2mm × 3mm
DFN package (both with an Exposed Pad for better thermal
characteristics).
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners.
Adjustable 500mA Single
®
3085 is a 500mA low dropout linear regulator that
9.80
Resistor Low Dropout
SET PIN CURRENT DISTRIBUTION (μA)
N = 1676
9.90
10.00
10.10
Regulator
3085 TA01b
10.20
LT3085
1
3085f

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lt3085ems8e Summary of contents

Page 1

... The LT3085 is offered in the 8-lead MSOP and a low profi le (0.75mm) 6-lead 2mm × 3mm DFN package (both with an Exposed Pad for better thermal characteristics). L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. OUT V OUT 2.2μ ...

Page 2

... LT3085IMS8E#TRPBF LT3085MPMS8E#PBF LT3085MPMS8E#TRPBF LEAD BASED FINISH TAPE AND REEL LT3085EDCB LT3085EDCB#TR LT3085EMS8E LT3085EMS8E#TR LT3085IDCB LT3085IDCB#TR LT3085IMS8E LT3085IMS8E#TR LT3085MPMS8E LT3085MPMS8E#TR Consult LTC Marketing for parts specifi ed with wider operating temperature ranges. *The temperature grade is identifi label on the shipping container. ...

Page 3

ELECTRICAL CHARACTERISTICS temperature range, otherwise specifi cations are at T PARAMETER SET Pin Current I SET Output Offset Voltage (V – OUT SET OS ΔI Load Regulation SET ΔV OS ΔI Line Regulation SET ΔV OS Minimum ...

Page 4

LT3085 TYPICAL PERFORMANCE CHARACTERISTICS Set Pin Current 10.20 10.15 10.10 10.05 10.00 9.95 9.90 9.85 9. –50 – 100 125 TEMPERATURE (°C) 3085 G01 Offset Voltage Distribution N = 1676 –2 – DISTRIBUTION ...

Page 5

TYPICAL PERFORMANCE CHARACTERISTICS Dropout Voltage (Minimum IN Voltage) 400 350 I = 500mA LOAD 300 250 200 150 I = 100mA LOAD 100 50 0 –50 – 100 125 TEMPERATURE (°C) 3085 G10 Current Limit 700 ...

Page 6

LT3085 TYPICAL PERFORMANCE CHARACTERISTICS V Pin Currrent CONTROL 500mA 12 LOAD 10 DEVICE IN 8 CURRENT LIMIT 1mA LOAD INPUT-TO-OUTPUT DIFFERENTIAL (V) ...

Page 7

TYPICAL PERFORMANCE CHARACTERISTICS Error Amplifi er Gain and Phase 100mA LOAD 500mA LOAD 3 0 –3 –6 –9 10 100 1k FREQUENCY (Hz) PIN FUNCTIONS (DCB/MS8E) V (Pin 4/Pin 5): ...

Page 8

LT3085 BLOCK DIAGRAM APPLICATIONS INFORMATION The LT3085 regulator is easy to use and has all the pro- tection features expected in high performance regulators. Included are short-circuit protection and safe operating area protection, as well as thermal shutdown. The LT3085 ...

Page 9

APPLICATIONS INFORMATION The LT3085 can be operated in two modes. Three terminal mode has the control pin connected to the power input pin which gives a limitation of 1.35V dropout. Alternatively, the “control” pin can be tied to a higher ...

Page 10

LT3085 APPLICATIONS INFORMATION Input Capacitance and Stability The LT3085 is designed to be stable with a minimum capacitance of 1μF at each input pin. Ceramic capacitors with low ESR are available for use to bypass these pins, but in cases ...

Page 11

APPLICATIONS INFORMATION For improvement in transient performance, place a capaci- tor across the voltage setting resistor. Capacitors up to 1μF can be used. This bypass capacitor reduces system noise as well, but start-up time is proportional to the time constant ...

Page 12

LT3085 APPLICATIONS INFORMATION Voltage and temperature coeffi cients are not the only sources of problems. Some ceramic capacitors have a piezoelectric response. A piezoelectric device generates voltage across its terminals due to mechanical stress, ceramic capacitor the stress can be ...

Page 13

APPLICATIONS INFORMATION The first test was done with approximately 1.6V input- to-output and 0.5A per device. This gave a 800mW dissipation in each device and a 1A output current. The temperature rise above ambient is approximately 28°C and both devices ...

Page 14

LT3085 APPLICATIONS INFORMATION The resistor generates spot noise equal to√4kTR (k = -23 Boltzmann’s constant, 1.38 • 10 J/°K, and T is absolute temperature) which is RMS summed with the reference current noise. To lower reference noise, the voltage set- ...

Page 15

APPLICATIONS INFORMATION IN LT3085 V CONTROL + – OUT SET R SET Figure 7. Connections for Best Load Regulation Internal Parasitic Diodes and Protection Diodes In normal operation, the LT3085 does not require protection diodes. Older three-terminal regulators require protection ...

Page 16

LT3085 APPLICATIONS INFORMATION from junction to ambient. This includes junction-to-case, case-to-heat sink interface, heat sink resistance or circuit board-to-ambient as the application dictates. Additional heat sources nearby must also be considered. For surface mount devices, heat sinking is accomplished by ...

Page 17

APPLICATIONS INFORMATION The power in the output transistor equals – V )(I ) OUTPUT IN OUT OUT The total power equals TOTAL DRIVE OUTPUT The current delivered to the SET pin is ...

Page 18

LT3085 APPLICATIONS INFORMATION Without series resistor R , power dissipation in the LT3085 S equals: ⎛ ⎞ 0. – 3. – 3.3V P • ⎝ ⎜ ⎠ ⎟ TOTAL 60 = 0.86W If the ...

Page 19

TYPICAL APPLICATIONS 10V CONTROL 499k Higher Output Current MJ4502 50Ω IN LT3085 V CONTROL + 100μF – 1μF OUT SET 332k Current Source IN LT3085 V CONTROL + – 1μF ...

Page 20

LT3085 TYPICAL APPLICATIONS Adding Shutdown LT3085 CONTROL + – SET Q1 ON OFF R1 VN2222LL SHUTDOWN * Q2 INSURES ZERO OUTPUT IN THE ABSENCE OF ANY OUTPUT LOAD 12V V CONTROL C1 1μF ...

Page 21

TYPICAL APPLICATIONS 4.8V to 28V LT3085 28V V CONTROL + – C1 1.5μF SET R1 249k Adding Soft-Start LT3085 CONTROL + D1 C1 1N4148 1μF – SET C2 R1 0.01μF 332k ...

Page 22

LT3085 TYPICAL APPLICATIONS 12V TO 18V V CONTROL + 15μF SET 10k V IN 50V BUZ11 + 10μ Lab Supply LT3085 IN V CONTROL + 1Ω – 0.25W OUT + 15μF 50k 0A ...

Page 23

TYPICAL APPLICATIONS 10μF *4mV DROP ENSURES LT3085 IS OFF WITH NO LOAD MULTIPLE LT3085’S CAN BE USED Reference Buffer IN LT3085 V CONTROL + – OUT INPUT SET OUTPUT LT1019 C1 3085 TA11 GND 1μF Ground Clamp ...

Page 24

LT3085 TYPICAL APPLICATIONS Low Voltage, High Current Adjustable High Effi ciency Regulator † 2. 100μF LTC3414 2.2MEG 100k ×2 PGOOD RUN/SS 1000pF SYNC/MODE SGND *DIFFERENTIAL VOLTAGE ON LT3085 IS 0.6V SET BY THE ...

Page 25

TYPICAL APPLICATIONS CMDSH-4E † 4.5V TO 25V V IN 10μF 1μF LT3493 100k SHDN 0.1μF *DIFFERENTIAL VOLTAGE ON LT3085 ≈ 1.4V SET BY THE TPO610L P-CHANNEL THRESHOLD. † MAXIMUM OUTPUT VOLTAGE IS 2V BELOW INPUT VOLTAGE Adjustable High Effi ciency ...

Page 26

LT3085 PACKAGE DESCRIPTION 1.65 0.05 3.55 0.05 (2 SIDES) 2.15 0.05 RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS PIN 1 BAR TOP MARK (SEE NOTE 6) 0.200 REF NOTE: 1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF ...

Page 27

... LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. ...

Page 28

... Converter LTC3406/LTC3406B 600mA (I ), 1.5MHz Synchronous Step-Down OUT DC/DC Converter LTC3411 1.25A (I ), 4MHz Synchronous Step-Down DC/DC OUT Converter VLDO and ThinSOT are trademarks of Linear Technology Corporation. Linear Technology Corporation 28 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 ● Paralleling Regulators IN LT3080 V CONTROL + – ...

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