NSC LMV7235M7 45 nsec, ultra low power, low voltage, rail-to-rail input comparator with open-drain/push-pull output Datasheet

LMV7235/LMV7239
45 nsec, Ultra Low Power, Low Voltage, Rail-to-Rail Input
Comparator with Open-Drain/Push-Pull Output
General Description
Features
The LMV7235/LMV7239 are ultra low power, low voltage, 45
nsec comparators. They are guaranteed to operate over the
full supply voltage range of 2.7V to 5V. These devices
achieve a 45 nsec propagation delay while consuming only
65µA of supply current at 5V.
The LMV7235/LMV7239 have a greater than rail-to-rail common mode voltage range. The input common mode voltage
range extends 200mV below ground and 200mV above
supply, allowing both ground and supply sensing.
The LMV7235 features an open drain output. By connecting
an external resistor, the output of the comparator can be
used as a level shifter.
(VS = 5V, TA = 25˚C, Typical values unless otherwise specified)
n Propagation delay
45 nsec
n Low supply current
65µA
n Rail-to-Rail input
n Open drain and push-pull output
n Ideal for 2.7V and 5V single supply applications
n Available in space saving packages
— 5-pin SOT23
— 5-pin SC70
The LMV7239 features a push-pull output stage. This feature
allows operation without the need of an external pull-up
resistor.
The LMV7235/LMV7239 are available in the 5-Pin SC70 and
5-Pin SOT23 packages, which are ideal for systems where
small size and low power is critical.
Applications
n
n
n
n
n
n
n
Portable and battery powered systems
Scanners
Set top boxes
High speed differential line receiver
Window comparators
Zero-crossing detectors
High speed sampling circuits
Typical Application
10135902
Crystal Oscillator
© 2006 National Semiconductor Corporation
DS101359
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LMV7235/LMV7239 45 nsec, Ultra Low Power, Low Voltage, Rail-to-Rail Input Comparator with
Open-Drain/Push-Pull Output
August 2006
LMV7235/LMV7239
Connection Diagram
5-Pin SC70/SOT23
10135903
Top View
Ordering Information
Package
Part Number
LMV7235M7
5-pin SC70
LMV7235M7X
LMV7239M7
LMV7239M7X
LMV7235M5
5-pin SOT23
LMV7235M5X
LMV7239M5
LMV7239M5X
Marking
C21
C20
C21A
C20A
Supplied as
NSC Drawing
1k Units Tape and Reel
3k Units Tape and Reel
1k Units Tape and Reel
MAA05A
3k Units Tape and Reel
1k Units Tape and Reel
3k Units Tape and Reel
1k Units Tape and Reel
MF05A
3k Units Tape and Reel
Simplified Schematic
10135901
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2
Wave Soldering (10 sec)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
ESD Tolerance (Note 2)
Human Model Body
(V ) +0.3V, (V−) −0.3V
Current at Input Pin (Note 9)
± 10mA
Supply Voltages (V+ - V−)
100V
Differential Input Voltage
Voltage at Input/Output Pins
Operating Ratings
1000V
Machine Body
260˚C (lead temp)
+
2.7V to 5V
± Supply Voltage
Temperature Range (Note 4)
−40˚C to +85˚C
(Note 3)
Storage Temperature Range
−65˚C to +150˚C
Output Short Circuit Duration
Supply Voltage (V+ - V−)
Package Thermal Resistance
5.5V
Soldering Information
Infrared or Convection (20 sec)
235˚C
5-Pin SC70
478˚C/W
5-Pin SOT23
265˚C/W
2.7V Electrical Characteristics
Unless otherwise specified, all limits guaranteed for TA = 25˚C, VCM = V+/2, V+ = 2.7V, V− = 0V−. Boldface limits apply at the
temperature extremes.
Symbol
Parameter
Conditions
Min
(Note 6)
Typ
(Note 5)
Max
(Note 6)
Units
VOS
Input Offset Voltage
0.8
6
8
mV
IB
Input Bias Current
30
400
600
nA
IOS
Input Offset Current
5
200
400
nA
CMRR
Common Mode Rejection Ratio
0V < VCM < 2.7V
(Note 7)
PSRR
Power Supply Rejection Ratio
V+ = 2.7V to 5V
VCM
Input Common-Mode Voltage Range CMRR > 50dB
V −0.1
V−
−0.2 to
2.9
VO
Output Swing High
(LMV7239 only)
V+ −0.35
V+ −0.26
V
IL = 0.4mA,
VID = 500mV
V+ −0.02
V
IL = −4mA,
VID = −500mV
230
IL = −0.4mA,
VID = −500mV
15
mV
Sourcing, VO = 0V
(LMV7239 only)
(Note 3)
15
mA
Sinking, VO = 2.7V
(LMV7235 RL = 10k) (Note 3)
20
mA
Output Swing Low
(LMV7239/LMV7235)
ISC
Output Short Circuit Current
IL = 4mA,
VID = 500mV
52
62
65
85
−
dB
dB
+
V +0.1
V+
350
450
V
mV
IS
Supply Current
No load
52
tPD
Propagation Delay
Overdrive = 20mV
(Note 10)
68
ns
Overdrive = 50mV
(Note 10)
63
ns
Overdrive = 100mV
(Note 10)
50
ns
(Note 8)
5
ns
tSKEW
Propagation Delay Skew
(LMV7239 only)
3
85
100
µA
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LMV7235/LMV7239
Absolute Maximum Ratings (Note 1)
LMV7235/LMV7239
2.7V Electrical Characteristics
(Continued)
Unless otherwise specified, all limits guaranteed for TA = 25˚C, VCM = V+/2, V+ = 2.7V, V− = 0V−. Boldface limits apply at the
temperature extremes.
Symbol
Parameter
Output Rise Time
tr
Output Fall Time
tf
Conditions
Min
(Note 6)
Typ
(Note 5)
Max
(Note 6)
Units
LMV7239
10% to 90%
1.7
ns
LMV7235
10% to 90%
(Note 10)
112
ns
90% to 10%
1.7
ns
3
nA
ILEAKAGE Output Leakage Current
(LMV7235 only)
5V Electrical Characteristics
Unless otherwise specified, all limits guaranteed for TA = 25˚C, VCM = V+/2, V+ = 5V, V− = 0V. Boldface limits apply at the
temperature extremes.
Symbol
Parameter
Conditions
Min
(Note 6)
Typ
(Note 5)
Limits
(Note 6)
Units
VOS
Input Offset Voltage
1
6
8
mV
IB
Input Bias Current
30
400
600
nA
IOS
Input Offset Current
5
200
400
nA
CMRR
Common Mode Rejection Ratio
0V < VCM < 5V
52
67
dB
PSRR
Power Supply Rejection Ratio
V+ = 2.7V to 5V
65
85
dB
VCM
Input Common-Mode Voltage Range
CMRR > 50dB
V− −0.1
V−
−0.2 to
5.2
VO
Output Swing High
(LMV7239 only)
IL = 4mA,
VID = 500mV
V+ −0.25
V+ −0.15
V
IL = 0.4mA,
VID = 500mV
V+ −0.01
V
IL = −4mA,
VID = −500mV
230
IL = −0.4mA,
VID = −500mV
10
Output Swing Low
(LMV7239/LMV7235)
ISC
Output Short Circuit Current
Sourcing, VO = 0V
(LMV7239 only)
(Note 3)
25
15
55
Sinking, VO = 5V
(LMV7235 RL = 10k)
(Note 3)
30
20
60
V+ +0.1
V+
350
450
V
mV
mV
mA
mA
IS
Supply Current
No load
65
tPD
Propagation Delay
Overdrive = 20mV
(Note 10)
62
ns
Overdrive = 50mV
(Note 10)
57
ns
Overdrive = 100mV
(Note 10)
45
ns
(Note 8)
5
ns
tSKEW
Propagation Delay Skew
(LMV7239 only)
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4
95
110
µA
(Continued)
Unless otherwise specified, all limits guaranteed for TA = 25˚C, VCM = V+/2, V+ = 5V, V− = 0V. Boldface limits apply at the
temperature extremes.
Symbol
tr
tf
Parameter
Output Rise Time
Output Fall Time
Conditions
Min
(Note 6)
Typ
(Note 5)
Limits
(Note 6)
Units
LMV7239
10% to 90%
1.2
ns
LMV7235
10% to 90%
(Note 10)
100
ns
90% to 10%
1.2
ns
3
nA
ILEAKAGE Output Leakeage Current
(LMV7235 only)
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is
intended to be functional, but specific performance is not guaranteed. For guaranteed specifications and the test conditions, see the Electrical characteristics.
Note 2: Human Body Model, applicable std. MIL-STD-883, Method 3015.7. Machine Model, applicable std. JESD22-A115-A (ESD MM std. of JEDEC)
Field-Induced Charge-Device Model, applicable std. JESD22-C101-C (ESD FICDM std. of JEDEC).
Note 3: Applies to both single-supply and split-supply operation. Continuous short circuit operation at elevated ambient temperature can result in exceeding the
maximum allowed junction temperature of 150˚C. Output currents in excess of ± 30mA over long term may adversely affect reliability.
Note 4: The maximum power dissipation is a function of TJ(MAX), θJA. The maximum allowable power dissipation at any ambient temperature is
PD = (TJ(MAX) – TA)/ θJA. All numbers apply for packages soldered directly onto a PC Board.
Note 5: Typical values represent the most likely parametric norm as determined at the time of characterization. Actual typical values may vary over time and will
also depend on the application and configuration. The typical values are not tested and are not guaranteed on shipped production material.
Note 6: All limits are guaranteed by testing or statistical analysis.
Note 7: CMRR is not linear over the common mode range. Limits are guaranteed over the worst case from 0 to VCC/2 or VCC/2 to VCC.
Note 8: Propagation Delay Skew is defined as the absolute value of the difference between tPDLH and tPDHL.
Note 9: Limiting input pin current is only necessary for input voltages that exceed absolute maximum input voltage ratings.
Note 10: A 10k pull-up resistor was used when measuring the LMV7235. The rise time of the LMV7235 is a function of the R-C time constant.
5
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LMV7235/LMV7239
5V Electrical Characteristics
LMV7235/LMV7239
Typical Performance Characteristics
(Unless otherwise specified, VS = 5V, CL = 10pF, TA = 25˚C).
Supply Current vs. Supply Voltage
Sourcing Current vs. Output Voltage
10135904
10135905
Sourcing Current vs. Output Voltage
Sinking Current vs. Output Voltage
10135906
10135907
Sinking Current vs. Output Voltage
Input Bias Current vs. Input Voltage
10135909
10135908
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Input Bias Current vs. Input Voltage
Propagation Delay vs. Temperature
10135911
10135910
Propagation Delay vs. Capacitive Load
Propagation Delay vs. Capacitive Load
10135912
10135913
Propagation Delay vs. Input Overdrive
Propagation Delay vs. Input Overdrive
10135914
10135915
7
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LMV7235/LMV7239
Typical Performance Characteristics (Unless otherwise specified, VS = 5V, CL = 10pF, TA =
25˚C). (Continued)
LMV7235/LMV7239
Typical Performance Characteristics (Unless otherwise specified, VS = 5V, CL = 10pF, TA =
25˚C). (Continued)
Propagation Delay vs. Common Mode Voltage
Propagation Delay vs. Common Mode Voltage
10135916
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10135917
8
The LMV7235/LMV7239 are single supply comparators with
45ns of propagation delay and only 65µA of supply current.
COMPARATOR WITH HYSTERESIS
The basic comparator configuration may oscillate or produce
a noisy output if the applied differential input voltage is near
the comparator’s offset voltage. This usually happens when
the input signal is moving very slowly across the comparator’s switching threshold. This problem can be prevented by
the addition of hysteresis or positive feedback.
The LMV7235/LMV7239 are rail-to-rail input and output. The
typical input common mode voltage range of −0.2V below
the ground to 0.2V above the supply. The LMV7235/
LMV7239 use a complimentary PNP and NPN input stage in
which the PNP stage senses common mode voltage near V−
and the NPN stage senses common mode voltage near V+.
If either of the input signals falls below the negative common
mode limit, the parasitic PN junction formed by the substrate
and the base of the PNP will turn on resulting in an increase
of input bias current.
If one of the input goes above the positive common mode
limit, the output will still maintain the correct logic level as
long as the other input stays within the common mode range.
However, the propagation delay will increase. When both
inputs are outside the common mode voltage range, current
saturation occurs in the input stage, and the output becomes
unpredictable.
The propagation delay does not increase significantly with
large differential input voltages. However, large differential
voltages greater than the supply voltage should be avoided
to prevent damage to the input stage.
INVERTING COMPARATOR WITH HYSTERESIS
The inverting comparator with hysteresis requires a three
resistor network that is referenced to the supply voltage VCC
of the comparator, as shown in Figure 1. When VIN at the
inverting input is less than VA, the voltage at the noninverting node of the comparator (VIN < VA), the output
voltage is high (for simplicity assume VO switches as high as
VCC). The three network resistors can be represented as
R1||R3 in series with R2. The lower input trip voltage VA1 is
defined as
VA1 = VCCR2 / ((R1||R3) + R2)
When VIN is greater than VA (VIN > VA), the output voltage is
low, very close to ground. In this case the three network
resistors can be presented as R2||R3 in series with R1. The
upper trip voltage VA2 is defined as
VA2 = VCC (R2||R3) / ((R1+ (R2||R3)
The LMV7239 has a push-pull output. When the output
switches, there is a direct path between VCC and ground,
causing high output sinking or sourcing current during the
transition. After the transition, the output current decreases
and the supply current settles back to about 65µA at 5V, thus
conserving power consumption.
The LMV7235 has an open drain that requires a pull-up
resistor to a positive supply voltage for the output to switch
properly. When the internal output transistor is off, the output
voltage will be pulled up to the external positive voltage.
The total hysteresis provided by the network is defined as
Delta VA = VA1- VA2
To assure that the comparator will always switch fully to VCC
and not be pulled down by the load the resistors, values
should be chosen as follow:
RPULL-UP << RLOAD
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LMV7235/LMV7239
Application Information
LMV7235/LMV7239
Application Information
(Continued)
10135919
FIGURE 1. Inverting Comparator with Hysteresis
NON-INVERTING COMPARATOR WITH HYSTERESIS
A non inverting comparator with hysteresis requires a two
resistor network, and a voltage reference (VREF) at the inverting input. When VIN is low, the output is also low. For the
output to switch from low to high, VIN must rise up to VIN1
where VIN1 is calculated by.
VIN1 = R1*(VREF/R2) + VREF
When VIN is high, the output is also high, to make the
comparator switch back to it’s low state, VIN must equal VREF
before VA will again equal VREF. VIN can be calculated by
VIN2 = (VREF (R1+ R2) - VCCR1)/R2
The hysteresis of this circuit is the difference between VIN1
and VIN2.
Delta VIN = VCCR1/R2
10135924
10135920
FIGURE 2. Non-Inverting Comparator with Hysteresis
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(Continued)
CRYSTAL OSCILLATOR
CIRCUIT LAYOUT AND BYPASSING
A simple crystal oscillator using the LMV7239 is shown
below. Resistors R1 and R2 set the bias point at the comparator’s non-inverting input. Resistors R3, R4 and C1 sets
the inverting input node at an appropriate DC average level
based on the output. The crystal’s path provides resonant
positive feedback and stable oscillation occurs. The output
duty cycle for this circuit is roughly 50%, but it is affected by
resistor tolerances and to a lesser extent by the comparator
offset.
The LMV7235/LMV7239 require high speed layout. Follow
these layout guidelines:
1. Use printed circuit board with a good, unbroken lowinductance ground plane.
2. Place a decoupling capacitor (0.1µF ceramic surface
mount capacitor) as close as possible to VCC pin.
3. On the inputs and the output, keep lead lengths as short
as possible to avoid unwanted parasitic feedback around the
comparator. Keep inputs away from output.
4. Solder the device directly to the printed circuit board rather
than using a socket.
5. For slow moving input signals, take care to prevent parasitic feedback. A small capacitor (1000pF or less) placed
between the inputs can help eliminate oscillations in the
transition region. This capacitor causes some degradation to
tPD when the source impedance is low.
6. The topside ground plane runs between the output and
inputs.
7. Ground trace from the ground pin runs under the device
up to the bypass capacitor, shielding the inputs from the
outputs.
10135922
FIGURE 5. Crystal Oscillator
ZERO-CROSSING DETECTOR
The inverting input is connected to ground and the noninverting input is connected to 100mVp-p signal. As the
signal at the non-inverting input crosses 0V, the comparator’s output changes state.
IR RECEIVER
The LMV7239 is an ideal candidate to be used as an infrared
receiver. The infrared photo diode creates a current relative
to the amount of infrared light present. The current creates a
voltage across RD. When this voltage level cross the voltage
applied by the voltage divider to the inverting input, the
output transitions.
10135918
FIGURE 3. Zero-Crossing Detector
THRESHOLD DETECTOR
Instead of tying the inverting input to 0V, the inverting input
can be tied to a reference voltage. The non-inverting input is
connected to the input. As the input passes the VREF threshold, the comparator’s output changes state.
10135923
FIGURE 6. IR Receiver
10135921
FIGURE 4. Threshold Detector
11
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LMV7235/LMV7239
Application Information
LMV7235/LMV7239
Physical Dimensions
inches (millimeters) unless otherwise noted
5-Pin SC70
NS Package Number MAA05A
5-Pin SOT23
NS Package Number MF05A
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12
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LMV7235/LMV7239 45 nsec, Ultra Low Power, Low Voltage, Rail-to-Rail Input Comparator with
Open-Drain/Push-Pull Output
Notes
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