參數(shù)資料
型號: AS1977-T
廠商: ams
文件頁數(shù): 5/18頁
文件大?。?/td> 0K
描述: IC COMPARATOR OPEN SOT23-5
標(biāo)準(zhǔn)包裝: 1
類型: 通用
元件數(shù): 1
輸出類型: CMOS,開路漏極,滿擺幅
電壓 - 電源,單路/雙路(±): 1.8 V ~ 5.5 V
電壓 - 輸入偏移(最小值): 5mV @ 5V
電流 - 輸入偏壓(最小值): 0.001µA @ 5V
電流 - 輸出(標(biāo)準(zhǔn)): 50mA
電流 - 靜態(tài)(最大值): 500nA
CMRR, PSRR(標(biāo)準(zhǔn)): 74dB CMRR,86.02dB PSRR
傳輸延遲(最大): 18ns
磁滯: 3mV
工作溫度: -40°C ~ 85°C
封裝/外殼: SC-74A,SOT-753
安裝類型: 表面貼裝
包裝: 標(biāo)準(zhǔn)包裝
其它名稱: AS1977-TDKR
www.austriamicrosystems.com
Revision 1.01
12 - 17
AS1976/AS1977
Data Sheet - A p p l i c a t i o n I n f o r m a t i o n
Additional Hysteresis (AS1976)
Additional hysteresis can be added to the AS1976 and AS1978 with three resistors and positive feedback (see Figure
27), however, this positive feedback method slows hysteresis response time.
Figure 27. AS1976 Additional Hysteresis
Resistor Selection Example
For the circuit shown in Figure 27, use the following steps to calculate values for R1, R2, and R3.
1. First select the value for R3. Leakage current at IN is less than 2nA, thus the current through R3 should be at least
0.2A to minimize errors due to leakage current. The current through R3 at the trip point is:
(VREF - VOUT)/R3
(EQ 1)
Taking into consideration the two possible output states, solving for R3 yields two formulas:
R3 = VREF/IR3
(EQ 2)
R3 = (VCC - VREF)/IR3
(EQ 3)
Use the smaller of the two resulting values for R3. For example, for VREF = 1.245V, VCC = 3.3V, and IR3 = 1A, the
two resistor values are 1.2M
Ω and 2.0MΩ, therefore choose a 1.2MΩ standard resistor for R3.
2. Choose the required hysteresis band (VHB). For this example, choose 33mV.
3. Calculate R1 as:
R1 = R3(VHB/VCC)(EQ 4)
Substituting the R1 and VHB example values gives:
R1 = 1.2M
Ω(50mV/3.3V) = 12kΩ
4. Choose the trip point for VIN rising (VTHR) such that VTHR > VREF(R1 + R3)/R3. For this example, choose 3V.
5. Calculate R2 as:
R2 = 1/[VTHR/(VREF x R1) - (1/R1) - (1/R3)]
(EQ 5)
Substituting the R1 and R3 example values gives:
R2 = 1/[3.0V/(1.2V x 12k
Ω) - (1/12kΩ) - (1/1.2MΩ)] = 8.05kΩ
In this example, a standard 8.2k
Ω resistor should be used for R2.
6. Verify the trip voltages and hysteresis as:
VTHR = VREF x R1[(1/R1) + (1/R2) + (1/R3)]
(EQ 6)
VTHF = VTHR - (R1 x VCC/R3)(EQ 7)
Hysteresis = VTHR - VTHF
(EQ 8)
OUT
R1
R3
VCC
VIN
VREF
R2
+
VEE
VCC
ams
AG
Technical
content
still
valid
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