參數(shù)資料
型號(hào): REF2912AIDBZRG4
英文描述: 100ppm/∑C, 50レA in SOT23-3 CMOS VOLTAGE REFERENCE
中文描述: 100ppm/ΣC,50レ的SOT23阿- 3 CMOS電壓基準(zhǔn)
文件頁(yè)數(shù): 8/16頁(yè)
文件大?。?/td> 412K
代理商: REF2912AIDBZRG4
REF2912, 2920, 2925, 2930, 2933, 2940
8
SBVS033A
www.ti.com
THEORY OF OPERATION
The REF29xx is a series, CMOS, precision bandgap voltage
reference. It
s basic topology is shown in Figure 1. The
transistors Q
1
, and Q
2
, are biased such that the current
density of Q
1
is greater than that of Q
2
. The difference of the
two base-emiter voltages, Vbe
1
Vbe
2
, has a positive
temperature coefficient and is forced across resistor R
1
. This
voltage is gained up and added to the base-emitter voltage
of Q
2
, which has a negative coefficient. The resulting output
voltage is virtually independent of temperature. The curvature
of the bandgap voltage, as seen in the typical curve,
Output
Voltage vs Temperature
, is due to the slightly nonlinear
temperature coefficient of the base-emitter voltage of Q
2
.
The REF29xx features a low quiescent current, which is
extremely stable over changes in both temperature and
supply. The typical room temperature quiescent current is
42
μ
A, and the maximum quiescent current over temperature
is just 59
μ
A. Additionally, the quiescent current typically
changes less than 2.5
μ
A over the entire supply range, as
shown in Figure 3.
1
3
REF29xx
2
0.47
μ
F
V
IN
V
OUT
FIGURE 1. Simplified Schematic of Bandgap Reference.
FIGURE 2. Typical Connections for Operating REF29xx.
42.5
42.0
41.5
41.0
40.5
40.0
I
Q
μ
A
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
6
V
IN
(V)
FIGURE 3. Supply Current vs Supply Voltage.
R
1
Q
2
Q
1
+
Vbe
1
+
Vbe
2
APPLICATION INFORMATION
The REF29xx does not require a load capacitor, and is stable
with any capacitive load. Figure 2 shows typical connections
required for operation of the REF29xx. A supply bypass
capacitor of 0.47
μ
F is recommended.
SUPPLY VOLTAGE
The REF29xx family of references features an extremely low
dropout voltage. With the exception of the REF2912, which
has a minimum supply requirement of 1.8V, the REF29xx
can be operated with a supply of only 1mV above the output
voltage in an unloaded condition. For loaded conditions, a
typical dropout voltage versus load is shown on the cover
page.
Supply voltages below the specified levels can cause the
REF29xx to momentarily draw currents greater than the
typical quiescent current. Using a power supply with a fast
rising edge and low output impedance easily prevents this.
THERMAL HYSTERESIS
Thermal hysteresis for the REF29xx is defined as the change
in output voltage after operating the device at 25
°
C, cycling
the device through the specified temperature range, and
returning to 25
°
C, and can be expressed as:
V
absV
V
V
ppm
(
HYST
PRE
POST
NOM
=
)
10
6
Where: V
HYST
=
Calculated hysteresis
V
PRE
= Output voltage measured at 25
°
C pre-
temperature cycling
V
POST
= Output voltage measured when device has
been operated at 25
°
C, cycled through specified
range
40
°
C to +125
°
C and returned to operation at
25
°
C
TEMPERATURE DRIFT
The REF29xx is designed to exhibit minimal drift error, defined
as the change in output voltage over varying temperature.
Using the
box
method of drift measurement, the REF29xx
features a typical drift coefficient of 20ppm from 0
°
C to 70
°
C
the primary temperature range of use for many applications.
For industrial temperature ranges of
40
°
C to 125
°
C, the
REF29xx family drift increases to a typical value of 50ppm.
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