MAX972MJA

更新时间： 2024-02-29 12:34:16

品牌	Logo	应用领域
美信 - MAXIM		比较器
页数	文件大小	规格书
16页	111K
描述
Ultra-Low-Power, Open-Drain, Single/Dual-Supply Comparators

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数据手册

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MAX972MJA 数据手册

Ult ra -Lo w -P o w e r, Op e n -Dra in ,

S in g le /Du a l-S u p p ly Co m p a ra t o rs

__________Ap p lic a t io n s In fo rm a t io n

V+

Hys t e re s is

Hysteresis increases the comparators’ noise margin by

increasing the upper threshold and decreasing the

lower threshold (Figure 2).

PULL-UP

Hysteresis (MAX9_1/MAX982/MAX9_3)

To add hysteresis to the MAX9_1, MAX982, or MAX9_3,

c onne c t re s is tor R1 b e twe e n REF a nd HYST, a nd

connect resistor R2 between HYST and V- (Figure 3). If

no hysteresis is required, connect HYST to REF. When

hysteresis is added, the upper threshold increases by

the same amount that the lower threshold decreases.

The hysteresis band (the difference between the upper

V+ OUT

V-

MAX9_4

GND

REF

and lower thresholds, V ) is approximately equal to

twice the voltage between REF and HYST. The HYST

input can be adjusted to a maximum voltage of REF

a nd to a minimum volta g e of (REF - 50mV). The

maximum difference between REF and HYST (50mV)

will therefore produce a 100mV max hysteresis band.

Use the following equations to determine R1 and R2:

Figure 4. External Hysteresis

Bo a rd La yo u t a n d Byp a s s in g

Power-supply bypass capacitors are not needed if the

supply impedance is low, but 100nF bypass capacitors

should be used when the supply impedance is high or

when the supply leads are long. Minimize signal lead

lengths to reduce stray capacitance between the input

and output that might cause instability. Do not bypass

the reference output.

R1 =

2 × I

(

)

REF

1.182 –

R2 =

REF

Win d o w De t e c t o r

The MAX9_3 is id e a l for ma king wind ow d e te c tors

(undervoltage/overvoltage detectors). The schematic is

shown in Figure 5, with component values selected for a

4.5V undervoltage threshold and a 5.5V overvoltage

threshold. Choose different thresholds by changing the

values of R1, R2, and R3. To prevent chatter at the

output when the supply voltage is close to a threshold,

hysteresis has been added using R4 and R5. Taken

alone, OUTA would provide an active-low undervoltage

ind ic a tion, a nd OUTB would g ive a n a c tive -low

overvoltage indication. Wired-ORing the two outputs

provides an active-high, power-good signal.

whe re I

(the c urre nt s ourc e d b y the re fe re nc e )

REF

s hould not e xc e e d the REF s ourc e c a p a b ility, a nd

s hould b e s ig nific a ntly la rg e r tha n the HYST inp ut

c urre nt.

usually appropriate. If 2.4MΩ is chosen for R2 (I

0.5µA), the e q ua tion for R1 a nd

approximated as:

va lue s b e twe e n 0.1µA a nd 4µA a re

REF

7/1–MAX984

c a n b e

R1 (kΩ) = V (mV)

Whe n hyste re sis is obta ine d in this ma nne r for the

MAX982/MAX9_3, the same hysteresis applies to both

comparators.

Hysteresis (MAX972/MAX9_4)

Hysteresis can be implemented with any comparator

using positive feedback, as shown in Figure 4. This

approach generally draws more current than circuits

using the HYST pin on the MAX9_1/MAX982/MAX9_3,

and the high feedback impedance slows hysteresis. In

addition, because the output does not source current,

any increase in the upper threshold is dependent on

the load or pull-up resistor on the output.

The design procedure is as follows:

1) Choose the required hysteresis level and calculate

values for R4 and R5 according to the formulas in

the Hysteresis (MAX9_1/MAX982/MAX9_3) section.

In this example, ±5mV of hysteresis has been added

at the comparator input (V = V / 2). This means

that the hysteresis apparent at V will be larger

because of the input resistor divider.

10 ______________________________________________________________________________________

1...7 8 91011 12 13...16

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与MAX972MJA相关器件

型号	品牌	获取价格	描述	数据表
MAX973	MAXIM	获取价格	Ultra-Low-Power.Open-Drain.Single/Dual-Supply Comparators
MAX973	ADI	获取价格	超低功耗、漏极开路输出、单/双电源比较器
MAX9730	MAXIM	获取价格	2.4W, Single-Supply, Class G Power Amplifier
MAX9730	ADI	获取价格	2.4W、单电源供电、G类功率放大器
MAX9730_07	MAXIM	获取价格	2.4W, Single-Supply, Class G Power Amplifier
MAX9730_10	MAXIM	获取价格	2.4W, Single-Supply, Class G Power Amplifier
MAX9730EBP+	MAXIM	获取价格	Audio Amplifier, 2.4W, 1 Channel(s), 1 Func, BICMOS, PBGA20, 2 X 2.50 MM, ROHS COMPLIANT,
MAX9730EBP+T	MAXIM	获取价格	2.4W, Single-Supply, Class G Power Amplifier
MAX9730EBPT	MAXIM	获取价格	2.4W, Single-Supply, Class G Power Amplifier
MAX9730ETI	MAXIM	获取价格	2.4W, Single-Supply, Class G Power Amplifier

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