參數(shù)資料
型號(hào): MAX9918ASA+T
廠商: Maxim Integrated Products
文件頁數(shù): 7/18頁
文件大小: 0K
描述: IC AMP CURRENT SENSE 8SOIC
標(biāo)準(zhǔn)包裝: 2,500
放大器類型: 電流檢測
電路數(shù): 1
輸出類型: 滿擺幅
轉(zhuǎn)換速率: 0.6 V/µs
-3db帶寬: 75kHz
電流 - 輸入偏壓: 175µA
電壓 - 輸入偏移: 400µV
電流 - 電源: 1mA
電壓 - 電源,單路/雙路(±): 4.5 V ~ 5.5 V
工作溫度: -40°C ~ 125°C
安裝類型: 表面貼裝
封裝/外殼: 8-SOIC(0.154",3.90mm Width)裸露焊盤
供應(yīng)商設(shè)備封裝: 8-SOICN 裸露焊盤
包裝: 帶卷 (TR)
MAX9918/MAX9919/MAX9920
-20V to +75V Input Range, Precision
Uni-/Bidirectional, Current-Sense Amplifiers
15
Maxim Integrated
Shutdown Mode
Drive SHDN high to enter low-power shutdown mode.
In shutdown mode, the MAX9918/MAX9919/MAX9920
draw 0.5μA (typ) of quiescent current.
Adjustable Gain (MAX9918/MAX9920)
The MAX9918/MAX9920 feature externally adjustable
gain set by a resistive-divider network circuit using
resistors R1 and R2 (see the
Functional Diagram). The
gain frequency compensation is set for a minimum gain
of 30V/V for the MAX9918 and 7.5V/V for the MAX9920.
The gain G for the MAX9918/MAX9920 is given by the
following equation:
Applications Information
Component Selection
Ideally, the maximum load current develops the full-
scale sense voltage across the current-sense resistor.
Choose the gain needed to yield the maximum output
voltage required for the application:
VOUT = VSENSE x G
where VSENSE is the full-scale sense voltage, 50mV for
the MAX9918/MAX9919, or 200mV for the MAX9920
and G is the gain of the device. G is externally
adjustable for the MAX9918/MAX9920. The MAX9919
has a fixed gain version of 45V/V (MAX9919F) or 90V/V
(MAX9919N).
In unidirectional applications (VREFIN = 0V), select the
gain of the MAX9918/MAX9920 to utilize the full output
range between GND and VCC. In bidirectional applica-
tions (VREFIN = VCC/2), select the gain to allow an output
voltage range of ±VCC/2. VOUT must be at least 100mV
from either rail to achieve the rated gain accuracy.
Sense Resistor, RSENSE
Choose RSENSE based on the following criteria:
Accuracy: A high RSENSE value allows lower currents
to be measured more accurately. This is because off-
sets become less significant when the sense voltage is
larger. In the linear region (100mV < VOUT < VCC
- 100mV), there are two components to accuracy: input
offset voltage (VOS) and gain error (GE). Use the linear
equation to calculate total error:
VOUT = (G ± GE) x (VSENSE ±VOS)
For best performance, select RSENSE to provide
approximately 50mV (MAX9918/MAX9919) or 200mV
(MAX9920) of sense voltage for the full-scale current in
each application. Sense resistors of 5m
Ω to 100mΩ are
available with 1% accuracy or better.
Efficiency and Power Dissipation
At high current levels, the I2R losses in RSENSE can be
significant. Take this into consideration when choosing
the resistor value and its power dissipation (wattage)
rating. Also, the sense resistor’s value might drift if it is
allowed to heat up excessively. The precision VOS of
the MAX9918/MAX9919/MAX9920 allows the use of
small sense resistors to reduce power dissipation and
reduce hot spots.
Inductance: Keep inductance low if ISENSE has a large
high-frequency component by using resistors with low
inductance value.
Power-Supply Bypassing and Grounding
Bypass the MAX9918/MAX9919/MAX9920’s VCC to
ground with a 0.1μF capacitor. Grounding these
devices requires no special precautions; follow the
same cautionary steps that apply to the rest of the sys-
tem. High-current systems can experience large volt-
age drops across a ground plane, and this drop may
add to or subtract from VOUT. Using a differential mea-
surement between OUT and REFIN prevents this prob-
lem. For highest current-measurement accuracy, use a
single-point star ground. Connect the exposed pad to a
solid ground to ensure optimal thermal performance.
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