LMH7322 www.ti.com SNOSAU8I – MARCH 2007 – REVISED MARCH 2013 LMH7322 Dual 700 ps High Speed Comparator with RSPECL Outputs Check for Samples: LMH7322 FEATURES DESCRIPTION • • • • • • The LMH7322 is a dual comparator with 700 ps propagation delay, low dispersion of 75 ps and an input voltage range that extends from VCC-1.5V to VEE. The devices can be operated from a wide supply voltage range of 2.7V to 12V. The adjustable hysteresis adds flexibility and prevents oscillations.
LMH7322 SNOSAU8I – MARCH 2007 – REVISED MARCH 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. Absolute Maximum Ratings ESD Tolerance (1) (2) (3) Human Body Model 2.5 kV Machine Model 250V Output Short Circuit Duration See (4) (5) (6) Supply Voltages (VCCx–VEE) 13.
LMH7322 www.ti.com SNOSAU8I – MARCH 2007 – REVISED MARCH 2013 12V DC Electrical Characteristics Unless otherwise specified, all limits are specified for TJ = 25°C, VCCI = VCCO = 12V, VEE = 0V, RL = 50Ω to VCCO-2V, VCM = 300 mV, RHYS = 1 kΩ. Boldface limits apply at temperature extremes. Symbol Parameter Conditions Min Typ −5 −2.
LMH7322 SNOSAU8I – MARCH 2007 – REVISED MARCH 2013 www.ti.com 12 AC Electrical Characteristics (continued) Unless otherwise specified, all limits are specified for TJ = 25°C, VCCI = VCCO = 12V, VEE = 0V, RL = 50Ω to VCCO-2V, VCM = 300 mV, RHYS = none.Boldface limits apply at temperature extremes. Symbol Parameter Min Conditions (1) Typ (2) tjitter-RMS RMS Random Jitter Overdrive = ±100 mV; CL = 2 pF Center Frequency = 140 MHz Bandwidth = 10 Hz–20 MHz 702 tPDH Propagation Delay.
LMH7322 www.ti.com SNOSAU8I – MARCH 2007 – REVISED MARCH 2013 5V DC Electrical Characteristics (continued) Unless otherwise specified, all limits are specified for TJ = 25°C, VCCI = VCCO = 5V, VEE = 0V, RL = 50Ω to VCCO-2V, VCM = 300 mV, RHYS = 1 kΩ.Boldface limits apply at temperature extremes. Symbol VRID-LE Parameter Conditions Min Typ (1) Max (2) Latch Enable Differential Voltage Range (1) Units ±0.4 V OUTPUT CHARACTERISTICS VOH Output Voltage High VCCO−1.
LMH7322 SNOSAU8I – MARCH 2007 – REVISED MARCH 2013 www.ti.com 2.7V DC Electrical Characteristics Unless otherwise specified, all limits are specified for TJ = 25°C, VCCI = VCCO = 2.7V, VEE = 0V, RL = 50Ω to VCCO-2V, VCM = 300 mV, RHYS = 1 kΩ. Boldface limits apply at temperature extremes. Symbol Parameter Conditions Min Typ −5 −2.
LMH7322 www.ti.com SNOSAU8I – MARCH 2007 – REVISED MARCH 2013 2.7V AC Electrical Characteristics (continued) Unless otherwise specified, all limits are specified for TJ = 25°C, VCCI = VCCO = 2.7V, VEE = 0V, RL = 50Ω to VCCO-2V, VCM = 300 mV, RHYS = none. Boldface limits apply at temperature extremes. Symbol Parameter tjitter_RMS tPDH tOD-disp Min Conditions (1) Typ (2) RMS Random Jitter Overdrive = ±50 mV; CL = 2 pF Center Frequency = 140 MHz Bandwidth = 10 Hz–20 MHz 551 Propagation Delay.
LMH7322 SNOSAU8I – MARCH 2007 – REVISED MARCH 2013 www.ti.com Typical Performance Characteristics At TJ = 25°C; VCCI = +5V; VCCO = +3.3V; VEE = −5V; unless otherwise specified. Propagation Delay vs. Temperature 1100 1050 1050 1000 PROPAGATION DELAY (ps) PROPAGATION DELAY (ps) Propagation Delay vs. Supply Voltage 1100 125°C 950 900 850 800 85°C 750 25°C 700 650 -40°C 600 2 3 4 VS = 12V 1000 950 900 850 VS = 2.
LMH7322 www.ti.com SNOSAU8I – MARCH 2007 – REVISED MARCH 2013 Typical Performance Characteristics (continued) At TJ = 25°C; VCCI = +5V; VCCO = +3.3V; VEE = −5V; unless otherwise specified. TPD Dispersion vs. Supply Voltage Slew Rate Dispersion vs. Voltage Supply 110 90 75 DISPERSION (ps) 80 70 60 VCM = 0.3V 50 VIN_DIFF = VCM - 100 mV 40 to VCM + VOVERDIVE 30 20 VOD = 50 mV - 1V 10 0 -10 2 4 5 6 7 8 9 VCM = 300 mV 65 SR = 0.
LMH7322 SNOSAU8I – MARCH 2007 – REVISED MARCH 2013 www.ti.com Typical Performance Characteristics (continued) At TJ = 25°C; VCCI = +5V; VCCO = +3.3V; VEE = −5V; unless otherwise specified. Output Voltage vs. Input Voltage Hysteresis Voltage vs. Hysteresis Resistor 70 0.3 VCM = 300 mV TEMP = 25°C 0.2 VS = 5V 0.1 HYSTERESIS VOLTAGE (mV) DIFFERENTIAL OUTPUT VOLTAGE (V) 0.4 = VHYS+ = VHYS- 0 RHYS = 32 k: -0.1 -0.2 RHYS = 0 -0.3 -0.4 -0.05 VS = 2.
LMH7322 www.ti.com SNOSAU8I – MARCH 2007 – REVISED MARCH 2013 APPLICATION INFORMATION Introduction The LMH7322 is a high speed comparator with RS(P)ECL (Reduced Swing Positive Emitter Coupled Logic) outputs, and is compatible with LVDS (Low Voltage Differential Signaling) if VCCO is set to 2.5V. The use of complementary outputs gives a high level of suppression for common mode noise. The very fast rise and fall times of the LMH7322 enable data transmission rates up to several Gigabits per second (Gbps).
LMH7322 SNOSAU8I – MARCH 2007 – REVISED MARCH 2013 www.ti.com The output stage of the LMH7322 is built using two emitter followers, which are referenced to the VCCO (see Figure 18.) Each of the output transistors is active when a current is flowing through any external output resistor connected to a lower supply rail. The output structure is actually the same as for all other ECL devices. Activating the outputs is done by connecting the emitters to a termination voltage which lies 2V below the VCCO.
LMH7322 www.ti.com SNOSAU8I – MARCH 2007 – REVISED MARCH 2013 Table 1. Definitions (continued) Symbol Text Description Hyst Hysteresis Difference between the switching point ‘0’ to ‘1’ and vice versa. IB-LE Latch Enable Bias Current Current flowing in or out of the input pins, when both are biased at normal PECL levels. IOS-LE Latch Enable Offset Current Difference between the input bias current of the LE and LE pin.
LMH7322 SNOSAU8I – MARCH 2007 – REVISED MARCH 2013 www.ti.com Table 1. Definitions (continued) Symbol Text Description thLE Latch Hold Time Time the input signal has to remain stable after enabling the latch functionality. tPD-LE Latch to Output Delay Time Delay time between the moment the latch input crosses the switching level H to L and the moment the differential output signal crosses the 50% level. Note: input signal is opposite to output signal when latch becomes enabled.
LMH7322 www.ti.com SNOSAU8I – MARCH 2007 – REVISED MARCH 2013 Table 2. PIN DESCRIPTIONS (continued) Pin Name Description Comment 8. INA+ Positive Input part A Input for analog voltages between 200 mV below VEEA and 2V below VCCIA. 9. RHREFA Reference Voltage Hysteresis Resistor part A The hysteresis voltage is determined by connecting a resistor from this pin to RHYSA. 10.
LMH7322 SNOSAU8I – MARCH 2007 – REVISED MARCH 2013 www.ti.com The DAP and the VEE Pins To ensure that both VEE pins are operating at the same voltage, both pins are connected to the DAP, and thus to each other, through bond wires. As a consequence, the DAP is at the same potential as the VEE pins and can be used to connect the device to the minimum supply voltage.
LMH7322 www.ti.com SNOSAU8I – MARCH 2007 – REVISED MARCH 2013 Interface from PECL to (RS)ECL The conversion from PECL to RS-ECL is possible when connecting the VCCI pin to +5V, which allows the input stage to handle these positive levels. The VCCO pin must be connected to the ground level in order to create the RSECL levels. The high level of the output of the LMH7322 is normally 1.1V below the VCCO supply voltage, and the low level is 1.5V below this supply.
LMH7322 SNOSAU8I – MARCH 2007 – REVISED MARCH 2013 www.ti.com 5V VCCO 2k5 Vin VCCO VCCI + IN+ Q IN- 1/2 LMH 7322 Q 10k 10k Levels: VOH = 3.9V VOL = 3.5V RHYS 10k VEE + LE LE RHREF VREF 1k 5k 5k Figure 25. Standard Setup Delay and Dispersion Comparators are widely used to connect the analog world to the digital one. The accuracy of a comparator is dictated by its DC properties, such as offset voltage and hysteresis, and by its timing aspects, such as rise and fall times and delay.
LMH7322 www.ti.com SNOSAU8I – MARCH 2007 – REVISED MARCH 2013 Input Signal If ΔtPD is not 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 will produce a symmetrical square wave at the output with a duty cycle of 50%. When tPDH and tPDL are different, the duty cycle of the output signal will not remain at 50%, but will be increased or decreased.
LMH7322 SNOSAU8I – MARCH 2007 – REVISED MARCH 2013 www.ti.com Overdrive 100 mV Input Differential Signal + Overdrive 10 mV 0 - Output Differential Signal time -100 mV Overdrive Dispersion + Dispersion 0 time - Figure 28. Overdrive Dispersion The overdrive dispersion is caused by the switching currents in the input stage which is dependent on the level of the differential input signal.
LMH7322 www.ti.com SNOSAU8I – MARCH 2007 – REVISED MARCH 2013 Input Differential Signal Vin cm + 0 Output Differential Signal - Vin cm time Common Mode Dispersion + Dispersion 0 time - Figure 30. Common Mode Dispersion All of the dispersion effects described previously influence the propagation delay. In practice the dispersion is often caused by a combination of more than one varied parameter.
LMH7322 SNOSAU8I – MARCH 2007 – REVISED MARCH 2013 www.ti.com Input Signal mV Vref fast output time 1 time slow output 0 1 time 0 t=0 t=1 Oscillations & Noise Figure 31. Oscillations on Output Signal In most circumstances this is not an option because the slew rate of the input signal will vary. Using Hysteresis Hysteresis can be introduced to avoid oscillations, e.g. due to noise on the input signal, especially for slow edges.
LMH7322 www.ti.com SNOSAU8I – MARCH 2007 – REVISED MARCH 2013 Configuring Hysteresis for the LMH7322 The LMH7322 offers the possibility to introduce hysteresis by connecting a resistor between the RHYS pin and the RHREF pin. This hysteresis setting resistor may vary between zero ohm and infinite. The current drawn from the RHYS pin determines the setting of the internal reference voltage.
LMH7322 SNOSAU8I – MARCH 2007 – REVISED MARCH 2013 www.ti.com Output Q VOH VOD VO VOL Output Q Figure 34. Output Swing Loading the Output Both outputs are activated when current is flowing through a resistor that is externally connected to VT. The termination voltage should be set 2V below the VCCO. This makes it possible to terminate each of the outputs directly with 50Ω, and if needed to connect through a transmission line with the same impedance (see Figure 35).
LMH7322 www.ti.com SNOSAU8I – MARCH 2007 – REVISED MARCH 2013 Transmission Lines & Termination Technologies The LMH7322 uses complementary RSPECL outputs and emitter followers, which means high output current capability and low sensitivity to parasitic capacitance. The use of Reduced Swing Positive Emitter Coupled Logic reduces the supply voltage to 2.7V, being the lowest possible value, and raises the maximum frequency response. Data rates are growing, which requires increasing speed.
LMH7322 SNOSAU8I – MARCH 2007 – REVISED MARCH 2013 www.ti.com These cables have a characteristic impedance determined by their geometric parameters. Widely used impedances for the coaxial cable are 50Ω and 75Ω. Twisted pair cables have impedances of about 120Ω to 150Ω. Other types of transmission lines are the strip line and the micro strip line. These last types are used on PCB boards.
LMH7322 www.ti.com SNOSAU8I – MARCH 2007 – REVISED MARCH 2013 PCB Layout Considerations and Component Value Selection High frequency designs require that both active and passive components be selected from those that are specially designed for this purpose. The LMH7322 is fabricated in a 24-pin WQFN package intended for surface mount design.
LMH7322 SNOSAU8I – MARCH 2007 – REVISED MARCH 2013 www.ti.com REVISION HISTORY Changes from Revision H (March 2013) to Revision I • 28 Page Changed layout of National Data Sheet to TI format ..........................................................................................................
PACKAGE OPTION ADDENDUM www.ti.
PACKAGE MATERIALS INFORMATION www.ti.com 26-Mar-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing LMH7322SQ/NOPB WQFN RTW 24 LMH7322SQE/NOPB WQFN RTW LMH7322SQX/NOPB WQFN RTW SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant 1000 178.0 12.4 4.3 4.3 1.3 8.0 12.0 Q1 24 250 178.0 12.4 4.3 4.3 1.3 8.0 12.0 Q1 24 4500 330.0 12.4 4.3 4.3 1.3 8.0 12.
PACKAGE MATERIALS INFORMATION www.ti.com 26-Mar-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LMH7322SQ/NOPB WQFN RTW 24 1000 213.0 191.0 55.0 LMH7322SQE/NOPB WQFN RTW 24 250 213.0 191.0 55.0 LMH7322SQX/NOPB WQFN RTW 24 4500 367.0 367.0 35.
MECHANICAL DATA RTW0024A SQA24A (Rev B) www.ti.
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