Datasheet

ManualsBrandsTEXAS INSTRUMENTS ManualsLinear ICsLinear IC - Comparator Multi-purpose Complementary, Differential, LVDS SOT 6

Sensor

LVDS input port

on receiver

100:

Ref

LMH7220

100:



Transmission Line

LMH7220

www.ti.com

SNOSAL3E –SEPTEMBER 2006–REVISED MAY 2013

LMH7220 High Speed Comparator with LVDS Output

Check for Samples: LMH7220

FEATURES

DESCRIPTION

The LMH7220 is a high speed, low power comparator

• (V

= 5V T

= 25°C, Typical Values unless

with an operating supply voltage range of 2.7V to

Otherwise Specified)

12V. The LMH7220 has a differential, LVDS output,

• Propagation Delay @ 100 mV Overdrive 2.9 ns

driving 325 mV into a 100Ω symmetrical transmission

• Rise and Fall Times 0.6 ns

line. The LMH7220 has a 2.9 ns propagation delay

and 0.6 ns rise and fall times while the supply current

• Supply Voltage 2.7V to 12V

is only 6.8 mA at 5V (load current excluded).

• Supply Current 6.8 mA

The LMH7220 inputs have a voltage range that

• Temperature Range −40°C to 125°C

extends 200 mV below ground, allowing ground

• LVDS Output

sensing applications. The LMH7220 is available in the

6-Pin SOT package. This package is ideal where

APPLICATIONS

space is a critical item.

• Acquisition Trigger

• Fast Differential Line Receiver

• Pulse Height Analyzer

• Peak Detector

• Pulse Width Modulator

• Remote Threshold Detection

• Oscilloscope Triggering

Figure 1. Typical Schematic

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of

Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

2All trademarks are the property of their respective owners.

PRODUCTION DATA information is current as of publication date.

Products conform to specifications per the terms of the Texas

Instruments standard warranty. Production processing does not

necessarily include testing of all parameters.

Summary of content (33 pages)

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LMH7220 www.ti.com SNOSAL3E – SEPTEMBER 2006 – REVISED MAY 2013 LMH7220 High Speed Comparator with LVDS Output Check for Samples: LMH7220 FEATURES DESCRIPTION • The LMH7220 is a high speed, low power comparator with an operating supply voltage range of 2.7V to 12V. The LMH7220 has a differential, LVDS output, driving 325 mV into a 100Ω symmetrical transmission line. The LMH7220 has a 2.9 ns propagation delay and 0.6 ns rise and fall times while the supply current is only 6.
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LMH7220 SNOSAL3E – SEPTEMBER 2006 – REVISED MAY 2013 www.ti.com These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates.
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LMH7220 www.ti.com SNOSAL3E – SEPTEMBER 2006 – REVISED MAY 2013 +12V DC ELECTRICAL CHARACTERISTICS Unless otherwise specified, all limits are specified for TJ = 25°C, VCM = 300 mV, −50 mV < VID < +50 mV and RL = 100Ω. Boldface limits apply at the temperature extremes. (1) (2) Symbol Parameter Conditions Min (1) Typ (3) Max (1) −2.1 −0.
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LMH7220 SNOSAL3E – SEPTEMBER 2006 – REVISED MAY 2013 www.ti.com +12V AC ELECTRICAL CHARACTERISTICS Unless otherwise specified, all limits specified for TJ = 25°C, VCM = 300 mV, −50 mV < VID < +50 mV and RL = 100Ω. Boldface limits apply at the temperature extremes.
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LMH7220 www.ti.com SNOSAL3E – SEPTEMBER 2006 – REVISED MAY 2013 +5V DC ELECTRICAL CHARACTERISTICS Unless otherwise specified, all limits specified for TJ = 25°C, VCM = 300 mV, −50 mV < VID < +50 mV and RL = 100Ω. Boldface limits apply at the temperature extremes. (1) (2) Symbol Parameter Conditions Min (1) Typ (3) Max (1) −1.5 −0.
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LMH7220 SNOSAL3E – SEPTEMBER 2006 – REVISED MAY 2013 www.ti.com +5V AC ELECTRICAL CHARACTERISTICS Unless otherwise specified, all limits specified for TJ = 25°C, VCM = 300 mV, −50 mV < VID < +50 mV and RL = 100Ω. Boldface limits apply at the temperature extremes.
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LMH7220 www.ti.com SNOSAL3E – SEPTEMBER 2006 – REVISED MAY 2013 +2.7V DC ELECTRICAL CHARACTERISTICS Unless otherwise specified, all limits specified for TJ = 25°C, VCM = 300 mV, −50 mV < VID < +50 mV and RL = 100Ω. Boldface limits apply at the temperature extremes. (1) Symbol Parameter Conditions Min (1) Typ (2) Max (1) −1.3 −0.
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LMH7220 SNOSAL3E – SEPTEMBER 2006 – REVISED MAY 2013 www.ti.com +2.7V AC ELECTRICAL CHARACTERISTICS Unless otherwise specified, all limits specified for TJ = 25°C, VCM = 300 mV, −50 mV < VID < +50 mV and RL = 100Ω. Boldface limits apply at the temperature extremes.
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LMH7220 www.ti.com SNOSAL3E – SEPTEMBER 2006 – REVISED MAY 2013 Connection Diagram 6 5 4 IN+ VCC OUT Q IN- GND OUT Q 1 2 3 Figure 3.
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LMH7220 SNOSAL3E – SEPTEMBER 2006 – REVISED MAY 2013 www.ti.com TYPICAL PERFORMANCE CHARACTERISTICS At TJ = 25°C; unless otherwise specified: VCM = 0.3V, VOVERDRIVE = 100 mV, RL = 100Ω. Input Current vs. Differential Input Voltage Bias Current vs. Supply Voltage 10 0.0 VCM = 300V 5 IIN+ IIN0 -5 VCM = 2.5V VS = 5V -10 IBIAS = (IIN+ + IIN-)/2 BIAS CURRENT (PA) INPUT CURRENT (PA) VIN_DIFF = 0 -0.5 -1.0 -1.5 -2.0 -2.5 VIN+ SWEEP = 1.6 to 3.4V VIN- SWEEP = 3.4V to 1.6V -15 -2 -1.5 -1 -0.
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LMH7220 www.ti.com SNOSAL3E – SEPTEMBER 2006 – REVISED MAY 2013 TYPICAL PERFORMANCE CHARACTERISTICS (continued) At TJ = 25°C; unless otherwise specified: VCM = 0.3V, VOVERDRIVE = 100 mV, RL = 100Ω. Differential Output Voltage vs. Temperature 14 VCM = 300 mV VIN_DIFF = 50 mV 12 0.36 SUPPLY CURRENT (mA) DIFFERENTIAL OUTPUT VOLTAGE (V) 0.38 Supply Current vs. Supply Voltage VS = 12V 0.34 0.32 VS = 5V VS = 2.7V 0.30 125°C 8 6 25°C LOAD CURRENT EXCLUDED Figure 11. Supply Current vs.
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LMH7220 SNOSAL3E – SEPTEMBER 2006 – REVISED MAY 2013 www.ti.com TYPICAL PERFORMANCE CHARACTERISTICS (continued) At TJ = 25°C; unless otherwise specified: VCM = 0.3V, VOVERDRIVE = 100 mV, RL = 100Ω. Propagation Delay vs. Common Mode Voltage Propagation Delay vs. Slew Rate 5.0 6.0 VIN- = VCM VIN+ = VCM - 50 mV to VCM + 50 mV PROPAGATION DELAY (ns) PROPAGATION DELAY (ns) 4.5 4.0 3.5 VS = 2.7V VS = 5V 3.0 VS = 12V 2.5 2.0 1.5 VCM = 0.3V 5.5 VIN- = VCM VIN+ = VCM - 100 mV to VCM + 100 mV 5.0 4.5 4.
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LMH7220 www.ti.com SNOSAL3E – SEPTEMBER 2006 – REVISED MAY 2013 APPLICATION INFORMATION INTRODUCTION The LMH7220 is a high speed comparator with LVDS outputs. The LVDS (Low Voltage Differential Signaling) standard uses differential outputs with a voltage swing of approximately 325 mV on each output. The most widely used setup for LVDS outputs consists of a switched current source of 3.25 mA.
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LMH7220 SNOSAL3E – SEPTEMBER 2006 – REVISED MAY 2013 www.ti.com The output can be seen as a bridge configuration in which switches are crosswise closed, producing the differential LVDS logic high and low levels (see Figure 20). The output switches are fed at top and bottom by two current sources. The top one is fixed and determines the differential voltage across the external load resistor. The other one is regulated and determines the common-mode voltage on the outputs.
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LMH7220 www.ti.
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LMH7220 SNOSAL3E – SEPTEMBER 2006 – REVISED MAY 2013 www.ti.
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LMH7220 www.ti.com SNOSAL3E – SEPTEMBER 2006 – REVISED MAY 2013 PW 80% 80% 50% 50% VIN 20% 20% tPDH tPDL 80% 80% Output Q 50% 50% 20% 20% tr tf Figure 22. Pulse Parameter Input Signal If ΔtPD isn’t zero, duty cycle distortion will occur. For example when applying a symmetrical waveform (e.g. a sinewave) at the input, it is expected that the comparator produces a symmetrical square wave at the output with a duty cycle of 50%.
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LMH7220 SNOSAL3E – SEPTEMBER 2006 – REVISED MAY 2013 www.ti.com Amplitude Overdrive Dispersion One of the parameters that causes dispersion is the amplitude variation of the input signal. Figure 24 shows the dispersion due to a variation of the input overdrive voltage. The overdrive is defined as the ‘goto’ differential voltage applied to the inputs. Figure 24 shows the impact it has on the propagation delay time if overdrive is varied from 10 millivolts to 100 millivolts.
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LMH7220 www.ti.com SNOSAL3E – SEPTEMBER 2006 – REVISED MAY 2013 A combination of overdrive- and slew rate dispersion occurs when applying signals with different amplitude at constant frequency. A small amplitude will produce a small voltage change per time unit (dV/dt) but also a small maximum switching current (overdrive) in the input transistors. High amplitudes produce a high dV/dt and a bigger overdrive.
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LMH7220 SNOSAL3E – SEPTEMBER 2006 – REVISED MAY 2013 www.ti.com slow output fast output Input Signal mV Vref time 1 time 0 1 time 0 t=0 t=1 Oscillations & Noise Figure 27. Oscillations & Noise In most circumstances this is not an option because the slew rate of the input signal will vary. Using Hysteresis A good way to avoid oscillations and noise during slow slopes is the use of hysteresis.
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LMH7220 www.ti.com SNOSAL3E – SEPTEMBER 2006 – REVISED MAY 2013 The divider RF-RP feeds back a portion of the output voltage to the positive input. Only a small part of the output voltage is needed, just enough to avoid the area at which the input is in an undefined state. Assuming this is only a few millivolts, it is sufficient to add (plus or minus) 10 mV to the positive input to prevent the circuit from oscillations.
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LMH7220 SNOSAL3E – SEPTEMBER 2006 – REVISED MAY 2013 • • www.ti.com Place a capacitor CC of 1 pF and accept a big overshoot at the positive input being sure that the input stage is in a secure new position Place an extra CP of such a value that CC has a realistic value of say 1 pF (extra CP = ±500 pF). Position of Feedback Resistors Another important issue while using positive feedback is the placement of the resistors RP and RF.
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LMH7220 www.ti.com SNOSAL3E – SEPTEMBER 2006 – REVISED MAY 2013 LOADING THE OUTPUT The output structure creates a current (ILOOP see Figure 32) through an external differential load resistor of 100Ω nominal. This results in a differential output voltage of 325 mV. The outputs of the comparator are connected to tracks on a PCB. These tracks can be seen as a differential transmission line. The differential load resistor acts as a high frequency termination at the end of the transmission line.
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LMH7220 SNOSAL3E – SEPTEMBER 2006 – REVISED MAY 2013 www.ti.com Maximum Bitrates A very important specification in high speed circuits are the rise and fall times. In fact these determine the maximum toggle rate (TR) of the part. The LVDS standard specifies them at 0.26 ns to 1.5 ns. Rise and fall times are normally specified at 20% and 80% of the signal amplitude (60% difference). TR is defined as the bitrate at which the differential output voltage drops to 50% of its nominal value.
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LMH7220 www.ti.com xxxx xx xxxx xx xxxx xx xxxx SNOSAL3E – SEPTEMBER 2006 – REVISED MAY 2013 top copper signal line PCB FR4 bottom copper stripline signal line Top Copper PCB FR4 bottom copper Microstrip signal lines Top Copper x PCB FR4 bottom copper differential microstrip Figure 35. PCB Transmission Lines Differential Microstrip Line The transmission line which is ideally suited for LVDS signals is the differential micro strip line.
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LMH7220 SNOSAL3E – SEPTEMBER 2006 – REVISED MAY 2013 www.ti.com PCB LAYOUT CONSIDERATIONS AND COMPONENT VALUES SELECTION High frequency designs require that both active- and passive components are selected that are specially designed for this purpose. For reliable high speed design it is highly recommended also to use small surface mount passive components because these packages have low parasitic capacitance and low inductance simply because they have no leads to connect them to the PCB.
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LMH7220 www.ti.com SNOSAL3E – SEPTEMBER 2006 – REVISED MAY 2013 REVISION HISTORY Changes from Revision D (April 2013) to Revision E • Page Changed layout of National Data Sheet to TI format ..........................................................................................................
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PACKAGE OPTION ADDENDUM www.ti.
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PACKAGE MATERIALS INFORMATION www.ti.com 23-Sep-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant LMH7220MK/NOPB SOT DDC 6 1000 178.0 8.4 3.2 3.2 1.4 4.0 8.0 Q3 LMH7220MKX/NOPB SOT DDC 6 3000 178.0 8.4 3.2 3.2 1.4 4.0 8.
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PACKAGE MATERIALS INFORMATION www.ti.com 23-Sep-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LMH7220MK/NOPB SOT DDC 6 1000 210.0 185.0 35.0 LMH7220MKX/NOPB SOT DDC 6 3000 210.0 185.0 35.
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