MAX9092 Просмотр технического описания (PDF) - Maxim Integrated

Номер в каталоге

Компоненты Описание

производитель

MAX9092

General-Purpose, Low-Voltage, Dual/Quad, Tiny Pack Comparators

Maxim Integrated 

MAX9092/MAX9093/MAX9094/MAX9095

General-Purpose, Low-Voltage,

Dual/Quad, Tiny Pack Comparators

Detailed Description

The MAX9092/MAX9093/MAX9094/MAX9095 are low-

cost, general-purpose comparators that have a single-

supply +1.8V to +5V operating voltage range. The

common-mode input range extends from -0.1V below the

negative supply to within +0.8V of the positive supply.

They require approximately 65FA per comparator with a

5V supply and 50FA with a 2.7V supply.

The MAX9093/MAX9095 have 2mV of hysteresis for noise

immunity. This significantly reduces the chance of output

oscillations even with slow moving input signals. The ICs

are ideal for automotive applications because they oper-

ate from -40NC to +125NC. See the Typical Operating

Characteristics.

Applications Information

Hysteresis

Many comparators oscillate in the linear region of opera-

tion because of noise or undesired parasitic feedback.

This tends to occur when the voltage on one input is

equal or very close to the voltage on the other input. The

MAX9093/MAX9095 have internal hysteresis to counter

parasitic effects and noise.

The hysteresis in a comparator creates two trip points:

one for the rising input voltage and one for the falling

input voltage (Figure 1). The difference between the trip

points is the hysteresis. When the comparator’s input

voltages are equal, the hysteresis effectively causes

one comparator input to move quickly past the other,

thus taking the input out of the region where oscillation

occurs. This provides clean output transitions for noisy,

slow-moving input signals.

Additional hysteresis can be generated with two resis-

tors using positive feedback (Figure 2). Use the following

procedure to calculate resistor values:

1) Find output voltage when output is high:

VOUT(HIGH) = VDD - ILOAD x RL

2) Find the trip points of the comparator using these

formulas:

VTH = VREF + ((VOUT(HIGH) - VREF)R2)/(R1 + R2)

VTL = VREF(1 - (R2/(R1 + R2)))

where VTH is the threshold voltage at which the compara-

tor switches its output from high to low as VIN rises above

the trip point, and VTL is the threshold voltage at which

the comparator switches its output from low to high as

VIN drops below the trip point.

3) The hysteresis band is:

VHYST = VTH - VTL = VDD(R2/(R1 + R2))

In this example, let VDD = 5V, VREF = 2.5V, ILOAD =

50nA, and RL = 5.1kI.

VOUT(HIGH) = 5.0V - (50 x 10-9 x 5.1 x 103I) ≈ 5.0V

VTH = 2.5 + 2.5(R2/(R1 + R2))

VTL = 2.5(1 - (R2/(R1 + R2)))

Select R2. In this example, choose 1kI.

Select VHYST. In this example, choose 50mV.

Solve for R1.

VHYST = VOUT(HIGH)(R2/(R1 + R2))V

0.050V = 5(1000/(R1 + 1000))V

where R1 ≈ 100kI, VTH = 2.525V, and VTL = 2.475V

IN+

THRESHOLDS

VDD

RL

R1

HYSTERESIS

VTH

IN-

VHYST

BAND

VTL

OUT

R2

IN+

VREF

IN-

VIN

VDD

OUT VOUT

MAX9093/MAX9095

VSS

Figure 1. Threshold Hysteresis Band (Not to Scale)

Figure 2. Adding Hysteresis with External Resistors

  9

Share Link: