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| 型号： | REF194GSZ |
| 厂商： | Analog Devices Inc |
| 文件页数： | 23/28页 |
| 文件大小： | 0K |
| 描述： | IC VREF SERIES PREC 4.5V 8-SOIC |
| 标准包装： | 98 |
| 系列： | REF19 |
| 基准类型： | 串联，精度 |
| 输出电压： | 4.5V |
| 容差： | ±10mV |
| 温度系数： | 25ppm/°C |
| 输入电压： | 4.6 V ~ 15 V |
| 通道数： | 1 |
| 电流 - 静态： | 15µA |
| 电流 - 输出： | 30mA |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 8-SOIC（0.154"，3.90mm 宽） |
| 供应商设备封装： | 8-SO |
| 包装： | 管件 |
| 产品目录页面： | 797 (CN2011-ZH PDF) |
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Data Sheet
Although this concept is simple, some cautions are needed. Because
the lower reference circuit must sink a small bias current from U2
(50 μA to 100 μA), plus the base current from the series PNP output
transistor in U2, either the external load of U1 or R1 must provide
a path for this current. If the U1 minimum load is not well defined,
V S
2
V S
REF19x
REF19x Series
Resistor R1 should be used, set to a value that conservatively passes
3
SLEEP
OUTPUT 6
R1
GND
I SY
ADJUST
V IN ≥ I OUT × R L (MAX) + V SY (MIN)
I OUT = + I SY (REF19x)
>> I SY
R SET
600 μA of current with the applicable V OUT1 across it. Note that the
two U1 and U2 reference circuits are locally treated as macrocells,
each having its own bypasses at input and output for best stability.
Both U1 and U2 in this circuit can source dc currents up to
their full rating. The minimum input voltage, V S , is determined by
the sum of the outputs, V OUT2 , plus the dropout voltage of U2.
A related variation on stacking two 3-terminal references is shown
in Figure 28, where U1, a REF192, is stacked with a 2-terminal
reference diode, such as the AD589. Like the 3-terminal stacked
reference shown in Figure 27, this circuit provides two outputs,
V OUT1 and V OUT2 , which are the individual terminal voltages of D1
and U1, respectively. Here this is 1.235 V and 2.5 V, which provides a
V OUT2 of 3.735 V. When using 2-terminal reference diodes, such as
D1, the rated minimum and maximum device currents must be
observed, and the maximum load current from V OUT1 can be no
greater than the current setup by R1 and V O (U1). When V O
(U1) is equal to 2.5 V, R1 provides a 500 μA bias to D1, so the
maximum load current available at V OUT1 is 450 μA or less.
+V S
V S > V OUT2 + 0.15V
2
1μF
4 R SET
P1
I OUT
V OUT R L
R SET
V OUT FOR EXAMPLE, REF195: V OUT = 5V
I OUT = 5mA
R1 = 953 ?
P1 = 100 ? , 10-TURN
Figure 29. A Low Dropout, Precision Current Source
SWITCHED OUTPUT 5 V/3.3 V REFERENCE
Applications often require digital control of reference voltages,
selecting between one stable voltage and a second. With the
sleep feature inherent to the REF19x series, switched output
reference configurations are easily implemented with little
additional hardware.
The circuit in Figure 30 shows the general technique, which takes
advantage of the output wire-OR capability of the REF19x device
family. When off, a REF19x device is effectively an open circuit
at the output node with respect to the power supply. When on, a
REF19x device can source current up to its current rating, but
C1
0.1 μ F
3
U1
REF192
4
6
V O (U1)
+
C2
1 μ F
R1
4.99k Ω
(SEE TEXT)
+V OUT2
3.735V
sink only a few μA (essentially, just the relatively low current of the
internal output scaling divider). Consequently, when two devices
are wired together at their common outputs, the output voltage
+ C3
D1
V O (D1)
+V OUT1
1.235V
AD589 1 μ F
V IN
COMMON
V OUT
COMMON
Figure 28. Stacking Voltage References with the REF192
PRECISION CURRENT SOURCE
is the same as the output voltage for the on device. The off state
device draws a small standby current of 15 μA (maximum), but
otherwise does not interfere with operation of the on device, which
can operate to its full current rating. Note that the two devices in
the circuit conveniently share both input and output capacitors,
and with CMOS logic drive, it is power efficient.
OUTPUT TABLE
In low power applications, the need often arises for a precision
U1/U2
V C *
V OUT (V)
current source that can operate on low supply voltages. As
shown in Figure 29, any one of the devices in the REF19x family
of references can be configured as a precision current source.
The circuit configuration illustrated is a floating current source
with a grounded load. The output voltage of the reference is
bootstrapped across R SET , which sets the output current into the
+V S = 6V
V C
1 2 3 4
U3A U3B
74HC04 74HC04
3
2
U1
REF19x
(SEE TABLE)
4
6
REF195/ HIGH 5.0
REF196 LOW 3.3
REF194/ HIGH 4.5
REF195 LOW 5.0
*CMOS LOGIC LEVELS
load. With this configuration, circuit precision is maintained for
load currents in the range from the reference’s supply current
+V OUT
(typically 30 μA) to approximately 30 mA. The low dropout
voltage of these devices maximizes the current source’s output
voltage compliance without excess headroom.
C1
0.1μF
3
2
U2
REF19x
(SEE TABLE)
4
6
+ C2
1μF
V IN
COMMON
Rev. L | Page 23 of 28
Figure 30. Switched Output Reference
V OUT
COMMON
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相关代理商/技术参数 |
参数描述 |
|---|---|
| REF194GSZ-REEL | 功能描述:IC VREF SERIES PREC 4.5V 8-SOIC RoHS:是 类别:集成电路 (IC) >> PMIC - 电压基准 系列:REF19 产品培训模块:Voltage Reference Basics 标准包装:100 系列:- 基准类型:旁路，精度 输出电压:4.096V 容差:±0.075% 温度系数:50ppm/°C 输入电压:- 通道数:1 电流 - 阴极:1µA 电流 - 静态:- 电流 - 输出:10mA 工作温度:0°C ~ 70°C 安装类型:表面贴装 封装/外壳:8-SOIC（0.154"，3.90mm 宽） 供应商设备封装:8-SOIC 包装:管件 |
| REF194GSZ-REEL7 | 功能描述:IC VREF SERIES PREC 4.5V 8SOIC RoHS:是 类别:集成电路 (IC) >> PMIC - 电压基准 系列:REF19 标准包装:3,000 系列:- 基准类型:旁路，精度 输出电压:3V 容差:±0.5% 温度系数:100ppm/°C 输入电压:- 通道数:1 电流 - 阴极:82µA 电流 - 静态:- 电流 - 输出:15mA 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:6-TSSOP（5 引线），SC-88A，SOT-353 供应商设备封装:SC-70-5 包装:带卷 (TR) 其它名称:296-20888-2 |
| REF195 | 制造商:AD 制造商全称:Analog Devices 功能描述:Precision Micropower, Low Dropout, Voltage References |
| REF1950008S | 制造商:Analog Devices 功能描述: |
| REF1950009S | 制造商:Analog Devices 功能描述: |
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