參數(shù)資料
型號: MAX923CPA+
廠商: Maxim Integrated Products
文件頁數(shù): 3/17頁
文件大?。?/td> 0K
描述: IC COMPARATOR W/REF 8-DIP
產品培訓模塊: Lead (SnPb) Finish for COTS
Obsolescence Mitigation Program
標準包裝: 50
類型: 帶電壓基準
元件數(shù): 2
輸出類型: CMOS,TTL
電壓 - 電源,單路/雙路(±): 2.5 V ~ 11 V,±1.25 V ~ 5.5 V
電壓 - 輸入偏移(最小值): 10mV @ 5V
電流 - 輸出(標準): 50mA
電流 - 靜態(tài)(最大值): 7.5µA
CMRR, PSRR(標準): 80dB CMRR,80dB PSRR
傳輸延遲(最大): 12µs
磁滯: 50mV
工作溫度: 0°C ~ 70°C
封裝/外殼: 8-DIP(0.300",7.62mm)
安裝類型: 通孔
包裝: 管件
產品目錄頁面: 1386 (CN2011-ZH PDF)
6. Verify the threshold voltages with these formulas:
Board Layout and Bypassing
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.
_______________Typical Applications
Auto-Off Power Source
Figure 5 shows the schematic for a 40mA power supply
that has a timed auto power-off function.
The
comparator output is the switched power-supply
output. With a 10mA load, it typically provides a
voltage of (VBATT – 0.12V), but draws only 3.5A
quiescent current. This circuit takes advantage of the
four key features of the MAX921: 2.5A supply current,
an internal reference, hysteresis, and high current
output. Using the component values shown, the three-
resistor voltage divider programs the maximum ±50mV
of hysteresis and sets the IN- voltage at 100mV. This
gives an IN+ trip threshold of approximately 50mV for
IN+ falling.
The RC time constant determines the maximum power-
on time of the OUT pin before power-down occurs.
This period can be approximated by:
R x C x 4.6sec
For example: 2M
Ω x 10F x 4.6 = 92sec. The actual
time will vary with both the leakage current of the
capacitor and the voltage applied to the circuit.
Window Detector
The MAX923 is ideal for making window detectors
(undervoltage/overvoltage detectors). The schematic
is shown in Figure 6, with component values selected
for an 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. OUTA provides an active-low undervoltage
indication, and OUTB gives an active-low overvoltage
indication. ANDing the two outputs provides an active-
high, power-good signal.
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 (MAX921/MAX923) section. In this
example, ±5mV of hysteresis has been added at the
comparator input (VH = VHB/2). This means that the
hysteresis apparent at VIN will be larger because of
the input resistor divider.
V
rising :
V
R1
1
R1
1
R2
1
R3
V
falling :
V
R1
V
R3
IN
THR
REF
IN
THF
THR
×
+
=
×+
()
MAX921–MAX924
Ultra Low-Power,
Single/Dual-Supply Comparators
______________________________________________________________________________________
11
MAX921
OUT
IN-
HYST
REF
V-
GND
IN+
V+
VBATT -0.15V
10mA
21
4
5
6
8
3
100k
1.1M
47k
4.5V TO 6.0V
MOMENTARY
SWITCH
7
R
C
Figure 5. Auto-off power switch operates on 2.5A quiescent
current.
相關PDF資料
PDF描述
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MAX923CSA+ 功能描述:校驗器 IC Dual Comparator w/1% Precision Ref RoHS:否 制造商:STMicroelectronics 產品: 比較器類型: 通道數(shù)量: 輸出類型:Push-Pull 電源電壓-最大:5.5 V 電源電壓-最小:1.1 V 補償電壓(最大值):6 mV 電源電流(最大值):1350 nA 響應時間: 最大工作溫度:+ 125 C 安裝風格:SMD/SMT 封裝 / 箱體:SC-70-5 封裝:Reel
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