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| 型号： | LM4140CCM-1.2/NOPB |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 基准电压源/电流源 |
| 英文描述： | LM4140 High Precision Low Noise Low Dropout Voltage Reference; Package: SOIC NARROW; No of Pins: 8; Qty per Container: 95/Rail |
| 中文描述： | 1-OUTPUT THREE TERM VOLTAGE REFERENCE, 1.25 V, PDSO8 |
| 封装： | SOIC-8 |
| 文件页数： | 2/15页 |
| 文件大小： | 881K |
| 代理商： | LM4140CCM-1.2/NOPB |
Application Hints (Continued)
MULTILAYER CERAMIC CAPACITORS
Surface-mountable multilayer ceramic capacitors may be an
attractive choice because of their relatively small physical
size and excellent RF characteristics.
However, they sometimes have an ESR values lower than
the minimum required by the LM4140, and relatively large
capacitance change with temperature. The manufacturer’s
datasheet for the capacitor should be consulted before se-
lecting a value. Test results of LM4140 stability using multi-
layer ceramic capacitors show that a minimum of 0.2F is
usually needed.
Multilayer ceramic capacitors that have been verified as
suitable for use with the LM4140 are shown in Table 2.
TABLE 2. Surface-Mount Ceramic Capacitors Selection
Guide
2.2F Surface-Mount Ceramic
Manufacturer
Part Number
Tokin
1E225ZY5U-C203
Murata
GRM42-6Y5V225Z16
4.7F Surface-Mount Ceramic
Tokin
1E475ZY5U-C304
REVERSE CURRENT PATH
The P-channel Pass transistor used in the LM4140 has an
inherent diode connected between the V
IN and VREF pins
(see diagram below).
10107903
Forcing the output to voltages higher than the input, or
pulling V
IN below voltage stored on the output capacitor by
more than a V
be, will forward bias this diode and current will
flow from the V
REF terminal to VIN. No damage to the
LM4140 will occur under these conditions as long as the
current flowing into the output pin does not exceed 50mA.
ON/OFF OPERATION
The LM4140 is designed to quickly reduce both V
REF and IQ
to zero when turned-off. V
REF is restored in less than 200s
when turned-on. During the turn-off, the charge across the
output capacitor is discharged to ground through internal
circuitry.
The LM4140 is turned-off by pulling the enable input low, and
turned-on by driving the input high. If this feature is not to be
used, the enable pin should be tied to the V
IN to keep the
reference on at all times (the enable pin must not be left
floating).
To ensure proper operation, the signal source used to drive
the enable pin must be able to swing above and below the
specified high and low voltage thresholds which guarantee
an ON or OFF state (see Electrical Characteristics).
The ON/OFF signal may come from either a totem-pole
output, or an open-collector output with pull-up resistor to the
LM4140 input voltage. This high-level voltage may exceed
the LM4140 input voltage, but must remain within the Abso-
lute Maximum Rating for the enable pin.
OUTPUT ACCURACY
Like all references, either series or shunt, the after assembly
accuracy is made up of primarily three components: initial
accuracy itself, thermal hysteresis and effects of the PCB
assembly stress.
LM4140 provides an excellent output initial accuracy of 0.1%
and temperature coefficient of 6ppm/C (B Grade).
For best accuracy and precision, the LM4140 junction tem-
perature should not exceed 70C.
The thermal hysteresis curve on this datasheet are perfor-
mance characteristics of three typical parts selected at ran-
dom from a sample of 40 parts.
Parts are mounted in a socket to minimize the effect of
PCB’s mechnical expansion and contraction. Readings are
taken at 25C following multiple temperature cycles to 0C
and 70C. The labels on the X axis of the graph indicates the
device temperature cycle prior to measurement at 25C.
The mechanical stress due to the PCB’s mechanical and
thermal stress can cause an output voltage shift more than
the true thermal coefficient of the device. References in
surface mount packages are more susceptible to these
stresses because of the small amount of plastic molding
which support the leads.
Following the recommendations on PCB Layout Consider-
ation section can minimize the mechanical stress on the
device.
PCB LAYOUT CONSIDERATION
The simplest ways to reduce the stress related shifts are:
1.
Mounting the device near the edges or the corners of the
board where mechanical stress is at its minimum. The
center of the board generally has the highest mechani-
cal and thermal expansion stress.
2.
Mechanical isolation of the device by creating an island
by cutting a U shape slot on the PCB for mounting the
device. This approach would also provide some thermal
isolation from the rest of the circuit.
Figure 5 is a recommended printed board layout with a slot
cut on three sides of the circuit layout to serve as a strain
relief.
10107933
FIGURE 4. Typical Thermal Hysteresis
LM4140
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相关PDF资料 |
PDF描述 |
|---|---|
| LM4140CCM-2.0/NOPB | LM4140 High Precision Low Noise Low Dropout Voltage Reference; Package: SOIC NARROW; No of Pins: 8; Qty per Container: 95/Rail |
| LM4140CCM-2.5/NOPB | LM4140 High Precision Low Noise Low Dropout Voltage Reference; Package: SOIC NARROW; No of Pins: 8; Qty per Container: 95/Rail |
| LM4140CCM-4.1/NOPB | LM4140 High Precision Low Noise Low Dropout Voltage Reference; Package: SOIC NARROW; No of Pins: 8; Qty per Container: 95/Rail |
| LM4140CCMX-1.0/NOPB | LM4140 High Precision Low Noise Low Dropout Voltage Reference; Package: SOIC NARROW; No of Pins: 8; Qty per Container: 2500/Reel |
| LM4140CCMX-1.2/NOPB | LM4140 High Precision Low Noise Low Dropout Voltage Reference; Package: SOIC NARROW; No of Pins: 8; Qty per Container: 2500/Reel |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LM4140CCM-2.0 | 功能描述:基准电压& 基准电流 RoHS:否 制造商:STMicroelectronics 产品:Voltage References 拓扑结构:Shunt References 参考类型:Programmable 输出电压:1.24 V to 18 V 初始准确度:0.25 % 平均温度系数（典型值）:100 PPM / C 串联 VREF - 输入电压（最大值）: 串联 VREF - 输入电压（最小值）: 分流电流（最大值）:60 mA 最大工作温度:+ 125 C 封装 / 箱体:SOT-23-3L 封装:Reel |
| LM4140CCM-2.0/NOPB | 功能描述:基准电压& 基准电流 RoHS:否 制造商:STMicroelectronics 产品:Voltage References 拓扑结构:Shunt References 参考类型:Programmable 输出电压:1.24 V to 18 V 初始准确度:0.25 % 平均温度系数（典型值）:100 PPM / C 串联 VREF - 输入电压（最大值）: 串联 VREF - 输入电压（最小值）: 分流电流（最大值）:60 mA 最大工作温度:+ 125 C 封装 / 箱体:SOT-23-3L 封装:Reel |
| LM4140CCM-2.5 | 功能描述:基准电压& 基准电流 RoHS:否 制造商:STMicroelectronics 产品:Voltage References 拓扑结构:Shunt References 参考类型:Programmable 输出电压:1.24 V to 18 V 初始准确度:0.25 % 平均温度系数（典型值）:100 PPM / C 串联 VREF - 输入电压（最大值）: 串联 VREF - 输入电压（最小值）: 分流电流（最大值）:60 mA 最大工作温度:+ 125 C 封装 / 箱体:SOT-23-3L 封装:Reel |
| LM4140CCM-2.5/NOPB | 功能描述:基准电压& 基准电流 PREC MICROPWR LDO VLTG REF RoHS:否 制造商:STMicroelectronics 产品:Voltage References 拓扑结构:Shunt References 参考类型:Programmable 输出电压:1.24 V to 18 V 初始准确度:0.25 % 平均温度系数（典型值）:100 PPM / C 串联 VREF - 输入电压（最大值）: 串联 VREF - 输入电压（最小值）: 分流电流（最大值）:60 mA 最大工作温度:+ 125 C 封装 / 箱体:SOT-23-3L 封装:Reel |
| LM4140CCM-4.1 | 功能描述:基准电压& 基准电流 RoHS:否 制造商:STMicroelectronics 产品:Voltage References 拓扑结构:Shunt References 参考类型:Programmable 输出电压:1.24 V to 18 V 初始准确度:0.25 % 平均温度系数（典型值）:100 PPM / C 串联 VREF - 输入电压（最大值）: 串联 VREF - 输入电压（最小值）: 分流电流（最大值）:60 mA 最大工作温度:+ 125 C 封装 / 箱体:SOT-23-3L 封装:Reel |
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