Datasheet

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LT1236

Precision Reference

ITY

ESCRIPTIO

The LT

1236 is a precision reference that combines ultra-

low drift and noise with excellent long-term stability and

high output accuracy. The reference output will both

source and sink up to 10mA and is almost totally immune

to input voltage variations. Two voltages are available: 5V

and 10V. The 10V version can be used as a shunt regulator

(two-terminal zener) with the same precision characteris-

tics as the three-terminal connection. Special care has

been taken to minimize thermal regulation effects and

temperature induced hysteresis.

The LT1236 combines both superior accuracy and tem-

perature coefficient specifications without the use of high

power, on-chip heaters. The LT1236 references are based

on a buried zener diode structure which eliminates noise

and stability problems with surface breakdown devices.

Further, a subsurface zener exhibits better temperature

drift and time stability than even the best band-gap

references.

■

Ultra-Low Drift: 5ppm/°C Max

■

Trimmed to High Accuracy: 0.05% Max

■

Industrial Temperature Range SO Package

■

Operates in Series or Shunt Mode

■

Pin Compatible with AD586, AD587

■

Output Sinks and Sources in Series Mode

■

Very Low Noise < 1ppm

P-P

(0.1Hz to 10Hz)

■

100% Noise Tested

■

> 100dB Ripple Rejection

■

Minimum Input/Output Differential of 1V

, LTC and LT are registered trademarks of Linear Technology Corporation.

Typical Distribution of Temperature Drift

Basic Positive and Negative Connections

LT1236

OUT

GND



LT1236-10

OUT

GND



OUT

–V

OUT

R1 =

OUT

– (V

–

)

LOAD

+ 1.5mA

–15V

–

)

LT1236 TA01

OUTPUT DRIFT (ppm/°C)

–3

UNITS (%)

–2

–1 0 1

LT1236 TA02

DISTRIBUTION 

OF THREE RUNS

■

A/D and D/A Converters

■

Precision Regulators

■

Precision Scales

■

Inertial Navigation Systems

■

Digital Voltmeters

Summary of content (12 pages)

PAGE 1
LT1236 Precision Reference U DESCRIPTIO FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ The LT®1236 is a precision reference that combines ultralow drift and noise with excellent long-term stability and high output accuracy. The reference output will both source and sink up to 10mA and is almost totally immune to input voltage variations. Two voltages are available: 5V and 10V. The 10V version can be used as a shunt regulator (two-terminal zener) with the same precision characteristics as the three-terminal connection.
PAGE 2
LT1236 W W W AXI U U ABSOLUTE RATI GS Input Voltage .......................................................... 40V Input/Output Voltage Differential ............................ 35V Output-to-Ground Voltage (Shunt Mode Current Limit) LT1236-5 ............................................................. 10V LT1236-10 ........................................................... 16V Trim Pin-to-Ground Voltage Positive................................................ Equal to VOUT Negative ................
PAGE 3
LT1236 ELECTRICAL CHARACTERISTICS VIN = 10V, IOUT = 0, TA = 25°C, unless otherwise noted. PARAMETER CONDITIONS Load Regulation (Sinking Current) (Note 3) 0 ≤ IOUT ≤ 10mA MIN LT1236-5 TYP MAX UNITS 60 100 150 ppm/mA ppm/mA 0.8 1.2 1.5 mA mA 3.5 µVP-P µVRMS ● Supply Current ● Output Voltage Noise (Note 5) 0.1Hz ≤ f ≤ 10Hz 10Hz ≤ f ≤ 1kHz 3.0 2.
PAGE 4
LT1236 ELECTRICAL CHARACTERISTICS VIN = 15V, IOUT = 0, TA = 25°C, unless otherwise noted. temperature. Output voltage is always measured at 25°C, but the IC is cycled to 50°C or 0°C before successive measurements. Hysteresis is roughly proportional to the square of temperature change. Hysteresis is not normally a problem for operational temperature excursions, but can be significant in critical narrow temperature range applications where the instrument might be stored at high or low temperatures.
PAGE 5
LT1236 U W TYPICAL PERFOR A CE CHARACTERISTICS Output Voltage Temperature Drift LT1236-5 Output Voltage Noise COUT = 0 FILTER = 1 POLE fLOW = 0.1Hz 14 5.004 OUTPUT VOLTAGE (V) 10 8 LT1236-10 4 3 5.003 5.002 5.001 100 1k BANDWIDTH (Hz) 5.000 –40 –20 10k 40 20 0 60 TEMPERATURE (°C) Sink Mode* Current Limit, LT1236-5 60 CURRENT INTO OUTPUT (mA) 1.4 1.2 TJ = – 55°C 1.0 TJ = 25°C TJ = 125°C 0.6 0.
PAGE 6
LT1236 U W TYPICAL PERFOR A CE CHARACTERISTICS Load Regulation, LT1236-10 10.0020 5 10.0015 4 VIN = 12V 10.0000 9.9995 9.9990 9.9985 9.9980 –40 –20 0 20 60 40 TEMPERATURE (˚C) 80 INPUT CURRENT (mA) 10.0005 2 1 0 –1 –2 2 4 6 8 SINKING TJ = 125°C 1.0 0.8 0.6 0 10 1.4 1.2 TJ = – 55°C 0.8 TJ = 25°C 0.4 TJ = 125°C 0 2 4 6 10 8 OUTPUT TO GROUND VOLTAGE (V) 35 40 Thermal Regulation, LT1236-10 INPUT PIN OPEN VIN = 30V ∆POWER = 200mW 50 40 30 20 LOAD REGULATION 0 – 0.5 –1.
PAGE 7
LT1236 U U W U APPLICATIONS INFORMATION Effect of Reference Drift on System Accuracy A large portion of the temperature drift error budget in many systems is the system reference voltage. This graph indicates the maximum temperature coefficient allowable if the reference is to contribute no more than 0.5LSB error to the overall system performance. The example shown is a 12-bit system designed to operate over a temperature range from 25°C to 65°C.
PAGE 8
LT1236 U W U U APPLICATIONS INFORMATION Kelvin Connections Although the LT1236 does not have true force/sense capability at its outputs, significant improvements in ground loop and line loss problems can be achieved with proper hook-up. In series mode operation, the ground pin of the LT1236 carries only ≈ 1mA and can be used as a sense line, greatly reducing ground loop and loss problems on the low side of the reference. The high side supplies load current so line resistance must be kept low.
PAGE 9
LT1236 U TYPICAL APPLICATIONS Boosted Output Current with No Current Limit Boosted Output Current with Current Limit ±10V Output Reference V+ ≥ VOUT + 2.8V V + ≥ (VOUT + 1.8V) D1* LED R1 220Ω R1 220Ω LT1236-10 8.2Ω 15V VOUT VIN 2N2905 2N2905 +10V GND IN IN LT1236 10V AT 100mA OUT GND + COM LT1236 10V AT 100mA OUT 2µF SOLID TANT GND + LT1236-10 VOUT V IN 2µF SOLID TANT GND –10V LT1236 TA05 *GLOWS IN CURRENT LIMIT, DO NOT OMIT –15V –10V R1 = ILOAD + 1.
PAGE 10
LT1236 U TYPICAL APPLICATIONS Negative Shunt Reference Driven by Current Source Strain Gauge Conditioner for 350Ω Bridge R1 357Ω 1/2W LT1236-10 28mA LT1236-10 15V IN OUT 28.5mA GND OUT 5V 350Ω STRAIN GAUGE BRIDGE** GND + 6 – 100pF 2 R4 20k LM301A† 1 2.
PAGE 11
LT1236 U TYPICAL APPLICATIONS Ultra-Linear Platinum Temperature Sensor* LT1236-10 IN OUT 20V GND R2* 5k R10 182k 1% R14 5k R1** 253k R9 100k R11 6.65M 1% R8 10M R15 10k Rf** 654k R12 1k R13 24.3k 20V R4 4.75k 1% R3** 5k RS† 100Ω AT 0°C 2 R5 200k 1% LT1001 3 R6 619k 1% R7 392k 1% –15V 7 – + 6 VOUT =100mV/°C –50°C ≤ T ≤ 150°C 4 –15V † STANDARD INDUSTRIAL 100Ω PLATINUM 4-WIRE SENSOR, ROSEMOUNT 78S OR EQUIVALENT. α = 0.
PAGE 12
LT1236 U PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. N8 Package 8-Lead Plastic DIP 0.300 – 0.325 (7.620 – 8.255) 0.045 – 0.065 (1.143 – 1.651) ( 0.130 ± 0.005 (3.302 ± 0.127) 0.065 (1.651) TYP 0.009 – 0.015 (0.229 – 0.381) +0.025 0.325 –0.015 +0.635 8.255 –0.381 0.400* (10.160) MAX 7 6 5 1 2 3 4 0.255 ± 0.015* (6.477 ± 0.381) 0.125 (3.175) MIN 0.045 ± 0.015 (1.143 ± 0.381) ) 8 0.015 (0.380) MIN 0.018 ± 0.003 (0.457 ± 0.076) 0.100 ± 0.010 (2.540 ± 0.