参数资料
型号: LM4041DYM3-1.2
厂商: MICREL INC
元件分类: 基准电压源/电流源
英文描述: 1-OUTPUT TWO TERM VOLTAGE REFERENCE, 1.225 V, PDSO3
封装: LEAD FREE, SOT-23, 3 PIN
文件页数: 5/16页
文件大小: 812K
代理商: LM4041DYM3-1.2
March 2005
13
M9999-031805
LM4040/4041
Micrel, Inc.
Applications Information
The stable operation of the LM4040 and LM4041 references
requires an external capacitor greater than 10nF connected
between the (+) and (–) pins. Bypass capacitors with values
between 100pF and 10nF have been found to cause the
devices to exhibit instabilities.
Schottky Diode
LM4040-x.x and LM4041-1.2 in the SOT-23 package have
a parasitic Schottky diode between pin 2 (–) and pin 3 (die
attach interface connect). Pin 3 of the SOT-23 package must
oat or be connected to pin 2. LM4041-ADJs use pin 3 as
the (–) output.
Conventional Shunt Regulator
In a conventional shunt regulator application (see Figure 1),
an external series resistor (RS) is connected between the
supply voltage and the LM4040-x.x or LM4041-1.2 reference.
RS determines the current that ows through the load (IL)
and the reference (IQ). Since load current and supply volt-
age may vary, RS should be small enough to supply at least
the minimum acceptable IQ to the reference even when the
supply voltage is at its minimum and the load current is at
its maximum value. When the supply voltage is at its maxi-
mum and IL is at its minimum, RS should be large enough so
that the current owing through the LM4040-x.x is less than
15mA, and the current owing through the LM4041-1.2 or
LM4041-ADJ is less than 12mA.
RS is determined by the supply voltage (VS), the load and
operating current, (IL and IQ), and the reference’s reverse
breakdown voltage (VR):
Rs = (Vs – VR) / (IL + IQ)
Adjustable Regulator
The LM4041-ADJ’s output voltage can be adjusted to any
value in the range of 1.24V through 10V. It is a function of
the internal reference voltage (VREF) and the ratio of the ex-
ternal feedback resistors as shown in Figure 2. The output
is found using the equation:
(1)
VO = VREF [ (R2/R1) + 1 ]
where VO is the desired output voltage. The actual value of
the internal VREF is a function of VO. The “corrected” VREF
is determined by:
(2)
VREF = VO (ΔVREF / ΔVO) + VY
where VO is the desired output voltage. ΔVREF /ΔVO is found
inthe“ElectricalCharacteristics”andistypically–1.3mV/Vand
VY is equal to 1.233V. Replace the value of VREF in equation
(1) with the value VREF found using equation (2).
Note that actual output voltage can deviate from that pre-
dicted using the typical ΔVREF / ΔVO in equation (2); for C-
grade parts, the worst-case ΔVREF / ΔVO is –2.5mV/V and
VY = 1.248V.
The following example shows the difference in output volt-
age resulting from the typical and worst case values of
ΔVREF / ΔVO.
Let VO = +9V. Using the typical values ofΔVREF /ΔVO , VREF
is 1.223V. Choosing a value of R1 = 10kΩ, R2 = 63.272kΩ.
Using the worst case ΔVREF / ΔVO for the C-grade and D-
grade parts, the output voltage is actually 8.965V and 8.946V
respectively. This results in possible errors as large as
0.39% for the C-grade parts and 0.59% for the D-grade parts.
Once again, resistor values found using the typical value of
ΔVREF / ΔVO will work in most cases, requiring no further
adjustment.
Figure 4. Voltage Level Detector
Figure 3. Voltage Level Detector
Typical Application Circuits
R1
120k
R2
1M
FB
+
LM4041-ADJ
D1
λ
< –12V
LED ON
R3
200
–5V
D1
λ
LM4041-
ADJ
R1
120k
R2
1M
FB
+
R3
330
> –12V
LED ON
–5V
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