LMX339 Maxim Integrated Products, Inc., LMX339 Datasheet - Page 8

• Manufacturer Part Number: LMX339
• Description: General-purpose, Low-voltage, Single/dual/quad, Tinypack Comparators
• Manufacturer: Maxim Integrated Products, Inc.

1) Find output voltage when output is high:
2) Find the trip points of the comparator using these
where V
parator switches its output from high to low as V
above the trip point, and V
which the comparator switches its output from low to
high as V
3) The hysteresis band will be:
In this example, let V
50nA, R
Select R2. In this example, we will choose 1kΩ.
Select V
Solve for R1:
General-Purpose, Low-Voltage,
Single/Dual/Quad, Tiny-Pack Comparators
Figure 2. Adding Hysteresis with External Resistors
8
V
V
V
REF
formulas:
V
V
V
0.050V = 5(1000 / (R1 + 1000)) V
OUT(HIGH)
IN
_______________________________________________________________________________________
TH
TL
HYST
V
= V
= V
L
HYST
TH
HYST
IN
R2
= 5.1kΩ:
= V
V
REF
REF
is the threshold voltage at which the com-
drops below the trip point.
V
TH
V
. In this example, we will choose 50mV.
OUT(HIGH)
TL
OUT(HIGH)
= V
= 5.0V - (50
(1 - (R2 / (R1 + R2)))
= 2.5V + 2.5V(R2 / (R1 + R2))
+ ((V
= 2.5V(1 - (R2 / (R1 + R2)))
TH
IN+
IN-
OUT(HIGH)
- V
R1
DD
TL
(R2 / (R1 + R2)) V
= V
= 5V, V
= V
TL
✕
DD
10
is the threshold voltage at
DD
V
V
V
-9
- I
- V
DD
DD
SS
(R2 / (R1 + R2))
LOAD
✕
REF
REF
5.1
)R2) / (R1 + R2)
LMX331
= 2.5V, I
✕
✕
R
L
10
R
OUT
L
3
Ω) ≈ 5.0V
LOAD
IN
V
OUT
rises
=
where R1 ≈ 100kΩ, V
Choose R1 and R2 to be large enough as not to exceed
the amount of current the reference can supply.
Choose R
current, yet small enough to supply the necessary cur-
rent to drive the load. R
10kΩ.
Use 0.1µF bypass capacitors from V
imize performance, minimize stray inductance by
putting this capacitor close to the V
ing trace lengths. For slow-moving input signals (rise
time > 1ms), use a 1nF capacitor between IN+ and IN-
to reduce high-frequency noise.
LMX331/LMX331H TRANSISTOR COUNT: 112
LMX393/LMX393H TRANSISTOR COUNT: 211
LMX339/LMX339H TRANSISTOR COUNT: 411
The source current required is V
The sink current is (V
L
to be large enough to avoid drawing excess
Board Layout and Bypassing
TH
= 2.525V, and V
OUT(HIGH)
L
should be between 1kΩ and
Chip Information
- V
REF
DD
DD
REF
/ (R1 + R2).
to V
TL
pin and reduc-
)
✕
= 2.475V.
SS
(R1 + R2).
. To max-