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參數(shù)資料
| 型號： | REF195FSZ-REEL |
| 廠商： | ANALOG DEVICES INC |
| 元件分類： | 基準電壓源/電流源 |
| 英文描述： | Precision Micropower, Low Dropout Voltage References |
| 中文描述： | 1-OUTPUT THREE TERM VOLTAGE REFERENCE, 5 V, PDSO8 |
| 封裝： | ROHS COMPLIANT, MS-012AA, SOIC-8 |
| 文件頁數(shù)： | 22/28頁 |
| 文件大?。?/td> | 407K |
| 代理商： | REF195FSZ-REEL |
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REF19x Series
Rev. I | Page 22 of 28
I
SY
ADJUST
R1
R
SET
P1
R
L
I
OUT
E.G., REF195: V
OUT
= 5V
I
= 5mA
R1 = 953
P1 = 100
, 10-TURN
V
IN
1μF
REF19x
2
3
4
6
V
IN
≥
I
OUT
× R
L
(MAX) + V
SY
(MIN)
I
OUT
=V
OUT
+ I
SY
(REF19x)
R
SET
V
OUT
>> I
SY
R
SET
V
IN
GND
V
REF
SLEEP
0
Figure 27. A Low Dropout, Precision Current Source
The governing equations for the circuit are
(
R
I
V
L
OUT
IN
)
(
)
19x
REF
Min
V
Max
SY
,
+
×
=
(
)
19x
REF
I
R
V
I
SY
SET
OUT
OUT
+
=
(
)
19x
REF
I
R
V
SY
SET
OUT
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 28 illustrates 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 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 is the same as the output voltage for the on
device. The off state device draws a small standby current of
15 μA (max), 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.
U3B
74HC04
U3A
74HC04
V
C
V
OUT
(V)
5.0
3.3
4.5
5.0
V
C
*
HI
LO
HI
LO
U1/U2
REF195/
REF196
REF194/
REF195
*CMOS LOGIC LEVELS
+V
S
= 6V
V
IN
COMMON
V
COMMON
C1
0.1μF
+V
OUT
C2
1μF
U1
(SEE TABLE)
2
3
4
U2
REF19x
(SEE TABLE)
2
3
4
+
6
6
1
3
2
4
OUTPUT TABLE
0
Figure 28. Switched Output Reference
Using dissimilar REF19x series devices with this configuration
allows logic selection between the U1/U2-specified terminal
voltages. For example, with U1 (a REF195) and U2 (a REF196),
as noted in the table in Figure 28, changing the CMOS-
compatible V
C
logic control voltage from HI to LO selects
between a nominal output of 5 V and 3.3 V, and vice versa.
Other REF19x family units can also be used for U1/U2, with
similar operation in a logic sense, but with outputs as per the
individual paired devices (see the table in Figure 28). Of course,
the exact output voltage tolerance, drift, and overall quality of
the reference voltage is consistent with the grade of individual
U1 and U2 devices.
Due to the nature of the wire-OR, one application caveat should
be understood about this circuit. Since U1 and U2 can only
source current effectively, negative going output voltage
changes, which require the sinking of current, necessarily takes
longer than positive going changes. In practice, this means that
the circuit is quite fast when undergoing a transition from 3.3 V
to 5 V, but the transition from 5 V to 3.3 V takes longer. Exactly
how much longer is a function of the load resistance, R
L
, seen at
the output and the typical 1 μF value of C2. In general, a
conservative transition time is approximately several milliseconds
for load resistances in the range of 100 Ω to 1 kΩ. Note that for
highest accuracy at the new output voltage, several time
constants should be allowed (>7.6 time constants for <1/2 LSB
error @ 10 bits, for example).
KELVIN CONNECTIONS
In many portable applications where the PC board cost and area
go hand-in-hand, circuit interconnects are very often narrow.
These narrow lines can cause large voltage drops if the voltage
reference is required to provide load currents to various
functions. The interconnections of a circuit can exhibit a typical
line resistance of 0.45 mΩ/square (1 oz. Cu, for example).
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| REF195G | 制造商:Analog Devices 功能描述: 制造商:Analog Devices 功能描述:Electronic Component |
| REF195GBC | 制造商:AD 制造商全稱:Analog Devices 功能描述:Precision Micropower, Low Dropout, Voltage References |
| REF195GP | 制造商:Analog Devices 功能描述:MICRO POWER 5 VOLT REF IC 制造商:Rochester Electronics LLC 功能描述:MICRO POWER 5VOLT REF IC - Bulk 制造商:Analog Devices 功能描述:Voltage Regulator IC Package/Case:8-SOIC |
| REF195GPZ | 功能描述:IC VREF SERIES PREC 5V 8-PDIP RoHS:是 類別:集成電路 (IC) >> PMIC - 電壓基準 系列:REF19 標準包裝:1,000 系列:- 基準類型:旁路，可調節(jié)，精度 輸出電壓:2.495 V ~ 36 V 容差:±0.5% 溫度系數(shù):標準值 34ppm/°C 輸入電壓:2.495 V ~ 36 V 通道數(shù):1 電流 - 陰極:1mA 電流 - 靜態(tài):- 電流 - 輸出:100mA 工作溫度:0°C ~ 70°C 安裝類型:表面貼裝 封裝/外殼:TO-243AA 供應商設備封裝:SOT-89-3 包裝:帶卷 (TR) |
| REF195GPZ | 制造商:Analog Devices 功能描述:Voltage Reference |
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