Datasheet

ManualsBrandsLINEAR TECHNOLOGY ManualsLinear ICsLinear IC - Comparator + lock CMOS, Complementary, TTL SOIC 8

LT1394

7ns, Low Power,

Single Supply, Ground-Sensing

Comparator

■

High Speed A/D Converters

■

Zero-Crossing Detectors

■

Current Sense for Switching Regulators

■

Extended Range V/F Coverters

■

Fast Pulse Height/Width Discriminators

■

High Speed Triggers

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Line Receivers

■

High Speed Sampling Circuits

Propagation Delay vs

Input Overdrive

OVERDRIVE (mV)

TIME (ns)

10 20 30 40

1394 TA02

PDLH

PDHL

= 25°C

STEP

= 100mV

= ±5V

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

UltraFast is a trademark of Linear Technology Corporation.

■

UltraFast

: 7ns

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Low Power: 6mA

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Low Offset Voltage: 0.8mV

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Operates Off Single 5V or Dual ±5V Supplies

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Input Common Mode Extends to Negative Supply

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No Minimum Input Slew Rate Requirement

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Complementary TTL Outputs

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Inputs Can Exceed Supplies without Phase Reversal

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Pin Compatible with LT1016, LT1116 and LT1671

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Output Latch Capability

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Available in 8-Lead MSOP and SO Packages

The LT

1394 is an UltraFast

(7ns) comparator with comple-

mentary outputs and latch. The input common mode range

extends from 1.5V below the positive supply down to the

negative supply rail. Like the LT1016, LT1116 and LT1671,

this comparator has complementary outputs designed to

interface directly to TTL or CMOS logic. The LT1394 may

operate from either a single 5V supply or dual ±5V supplies.

Low offset voltage specifications and high gain allow the

LT1394 to be used in precision applications.

The LT1394 is designed for improved speed and stability for

a wide range of operating conditions. The output stage

provides active drive in both directions for maximum speed

into TTL, CMOS or passive loads with minimal cross-conduc-

tion current. Unlike other fast comparators, the LT1394

remains stable even for slow transitions through the active

region, which eliminates the need to specify a minimum input

slew rate.

The LT1394 has an internal, TTL/CMOS compatible latch for

retaining data at the outputs. The latch holds data as long as

the LATCH pin is held high. Device parameters such as gain,

offset and negative power supply current are not significantly

affected by variations in negative supply voltage.

45MHz Single Supply Adaptive Trigger

–

LT1227

–

LT1006

INPUT

TRIGGER

OUT

1394 F18

500pF

0.1µF

510Ω

470Ω

750Ω

36Ω

10µF

0.1µF

0.005µF

100µF

Q1, Q2, Q3, Q4 = CA3096 ARRAY:

TIE SUBSTRATE (PIN 16) TO GROUND

= 1N4148

–

LT1394

Q1 Q2

FEATURES

DESCRIPTIO

APPLICATIO S

TYPICAL APPLICATIO

Summary of content (16 pages)

PAGE 1
LT1394 7ns, Low Power, Single Supply, Ground-Sensing Comparator DESCRIPTIO U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ UltraFastTM: 7ns Low Power: 6mA Low Offset Voltage: 0.
PAGE 2
LT1394 U W W W ABSOLUTE MAXIMUM RATINGS (Note 1) Total Supply Voltage (V+ to V–) ............................... 12V Positive Supply Voltage ............................................. 7V Negative Supply Voltage .......................................... – 7V Differential Input Voltage ....................................... ±12V Input and Latch Current (Note 2) ........................ ±10mA Output Current (Continuous)(Note 2) ................. ±20mA Operating Temperature Range ................
PAGE 3
LT1394 ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C. V + = 5V, V – = – 5V, VOUT(Q) = 1.4V, VLATCH = VCM = 0V unless otherwise noted. SYMBOL PARAMETER CONDITIONS VOL Output Voltage Swing Low IOUT = – 4mA IOUT = – 10mA I+ Positive Supply Current MIN ● TYP MAX UNITS 0.3 0.4 0.5 V V 6 8.5 10.0 mA mA 1.2 2.2 2.
PAGE 4
LT1394 U W TYPICAL PERFORMANCE CHARACTERISTICS Propagation Delay vs Load Capacitance Gain Characteristics 12 12 5.0 VS = ±5V IOUT = 0 4.5 TA = 125°C 4.0 10 10 tPDLH TA = 25°C 3.5 tPDHL 3.0 2.5 TA = –55°C 2.0 TIME (ns) 8 TIME (ns) OUTPUT VOLTAGE (V) Propagation Delay vs Positive Supply Voltage 6 4 1.5 1.0 0.5 0 0 –3 –2 0 1 2 –1 DIFFERENTIAL INPUT VOLTAGE (mV) 3 6 tPDLH 0 0 V – = –5V TA = 25°C VSTEP = 100mV OVERDRIVE = 5mV 2 10 20 30 40 OUTPUT LOAD CAPACITANCE (pF) 50 4.4 4.
PAGE 5
LT1394 U W TYPICAL PERFORMANCE CHARACTERISTICS Negative Common Mode Limit vs Temperature 1 0.8 0 5.0 VS = ±5V ∆VIN = 30mV 0.7 VS = SINGLE 5V –3 –4 VS = ±5V –5 0.5 TA = 125°C 0.4 50 25 75 0 TEMPERATURE (°C) 100 TA = –55°C 0.
PAGE 6
LT1394 U W TYPICAL PERFORMANCE CHARACTERISTICS tPD– Response Time to 5mV Overdrive tPD+ Response Time to 5mV Overdrive 1.4V 5mV + IN –95mV 1.4V Q OUT 5mV + IN Q OUT –95mV 0V VS = ±5V fIN = 2MHz VOD = 5mV VS = ±5V fIN = 2MHz VOD = 5mV 2ns/DIV 1394 G17 0V 2ns/DIV 1394 G18 U U U PIN FUNCTIONS V + (Pin 1): Positive Supply Voltage. Normally 5V. GND (Pin 6): Ground. +IN (Pin 2): Noninverting Input. Q OUT (Pin 7): Noninverting Logic Output.
PAGE 7
LT1394 U U W U APPLICATIONS INFORMATION Common Mode Considerations Input Bias Current The LT1394 is specified for a common mode range of – 5V to 3.5V on a ±5V supply or a common mode range of 0V to 3.5V on a single 5V supply. A more general consideration is that the common mode range is 0V below the negative supply and 1.5V below the positive supply, independent of the actual supply voltage.
PAGE 8
LT1394 U U W U APPLICATIONS INFORMATION 5V 0.01µF* 0V 25Ω –100mV 25Ω 0.1µF + 2N3866 10k V1** – Q 0.01µF 50Ω 0V –3V FET PROBE LT1394 130Ω PULSE IN Q FET PROBE * TOTAL LEAD LENGTH INCLUDING DEVICE PIN. SOCKET AND CAPACITOR LEADS SHOULD BE LESS THAN 0.5 IN. USE GROUND PLANE ** (VOS + OVERDRIVE)/200 50Ω 400Ω 750Ω –5V 1394 F02 –5V Figure 2. Response Time Test Circuit circuit is the lack of feedthrough from the generator to the comparator input.
PAGE 9
LT1394 U U W U APPLICATIONS INFORMATION Temperature-Compensated Crystal Oscillator (TXCO) 5V 1MHz TO 10MHz CRYSTAL (AT-CUT) 2k Figure 5 is a temperature-compensated crystal oscillator (TXCO). This circuit reduces oscillator temperature drift by inserting a temperature-dependent compensatory correction into the crystal’s frequency trimming network. This open-loop correction technique relies on cancellation of the temperature characteristics of the oscillator, which are quite repeatable.
PAGE 10
LT1394 U U W U APPLICATIONS INFORMATION 5.8M* LM134 A1 LT1077 2M 226Ω* 1M* + MV-209 VARACTOR DIODE 1M* – 2M 1µF 5V 10mV/°C 10k* 470k* 10M 0.01µF 10MHz 2k 10MHz 0.05ppm/°C + 5V 390Ω LT1394 0.01µF BAT-85 50k – 100k 2k 1µF 4.7k LT1004-1.2 + 0.068µF 1M FREQ SET 1394 F05 XTAL AT-CUT, 35° 25′ ANGLE * 1% FILM RESISTOR Figure 5. Temperature-Compensated 10MHz Crystal Oscillator.
PAGE 11
LT1394 U W U U APPLICATIONS INFORMATION Figure 8 shows waveforms for the high gain comparator. Trace A is a 500µV overdrive on a 1mV step applied to the circuit’s positive input (negative input grounded). Trace B shows the resulting amplified step at A1’s positive output. Trace C is A2’s band limited output. A1’s wideband output combines with A2’s DC corrected information to yield the correct, amplified composite signal at the LT1394’s positive input in Trace D. The LT1394’s output is Trace E.
PAGE 12
LT1394 U U W U APPLICATIONS INFORMATION 5V DELAY PROGRAMMING VOLTAGE INPUT 0V TO 3V = 0 TO 300ns DELAY A = 5V/DIV 0.1µF LT1634 100Ω B = 2V/DIV 1k 100Ω (DELAY CALIB) C = 5V/DIV 51pF 0.1µF D = 5V/DIV 330Ω Q2 Q4 Q1 100ns/DIV – LT1394 + 1000pF Q OUTPUT Q OUTPUT 330Ω Q3 220Ω TRIGGER INPUT 200ns MINIMUM Figure 12. Voltage-Controlled Delay’s Waveforms. Programming Voltage Determines Delay Between Input (Trace A) Falling Edge and Output (Trace D) Rising Edge.
PAGE 13
LT1394 U U W U APPLICATIONS INFORMATION Fast, High Impedance, Variable Threshold Trigger A frequent requirement in instrumentation is a fast trigger with a variable threshold. Often, a high impedance input is also required. Figure 15 meets these requirements. Comparator C1 is the basic trigger, with threshold voltage set at its negative input. Source follower Q1 provides high impedance with about 2pF input capacitance and 50pA bias current.
PAGE 14
LT1394 U U W U APPLICATIONS INFORMATION High Speed Adaptive Trigger Circuit Line and fibre-optic receivers often require an adaptive trigger to compensate for variations in signal amplitude and DC offsets. The circuit in Figure 18 triggers on 2mV to 175mV signals from 100Hz to 45MHz while operating from a single 5V rail. A1, operating at a gain of 15, provides wideband AC gain. The output of this stage biases a 2-way peak detector (Q1 through Q4).
PAGE 15
LT1394 U PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. MS8 Package 8-Lead Plastic MSOP (LTC DWG # 05-08-1660) 0.118 ± 0.004* (3.00 ± 0.102) 8 7 6 5 0.118 ± 0.004** (3.00 ± 0.102) 0.192 ± 0.004 (4.88 ± 0.10) 1 2 3 4 0.040 ± 0.006 (1.02 ± 0.15) 0.007 (0.18) 0.034 ± 0.004 (0.86 ± 0.102) 0° – 6° TYP 0.021 ± 0.006 (0.53 ± 0.015) SEATING PLANE 0.012 (0.30) 0.0256 REF (0.65) TYP 0.006 ± 0.004 (0.15 ± 0.
PAGE 16
LT1394 U TYPICAL APPLICATION 9 Voltage-Controlled Crystal Oscillator (VCXO) 14.3217MHz 8 FREQUENCY DEVIATION (kHz) Figure 20, a variant of the basic crystal oscillator, permits voltage tuning the output frequency. Such voltage-controlled crystal oscillators (VCXO) are often employed where slight variation of a stable carrier is required. This example is specifically intended to provide a 4 × NTSC sub-carrier tunable oscillator suitable for phase locking.