參數(shù)資料
型號(hào): MCP1700T-5002ETT
廠商: Microchip Technology Inc.
元件分類(lèi): 基準(zhǔn)電壓源/電流源
英文描述: Low Quiescent Current LDO
中文描述: 低靜態(tài)電流低壓降穩(wěn)壓器
文件頁(yè)數(shù): 14/24頁(yè)
文件大?。?/td> 638K
代理商: MCP1700T-5002ETT
MCP1700
DS21826B-page 14
2007 Microchip Technology Inc.
6.3
Voltage Regulator
Internal power dissipation, junction temperature rise,
junction temperature and maximum power dissipation
are calculated in the following example. The power
dissipation, as a result of ground current, is small
enough to be neglected.
6.3.1
POWER DISSIPATION EXAMPLE
Device Junction Temperature Rise
The internal junction temperature rise is a function of
internal power dissipation and the thermal resistance
from junction to ambient for the application. The thermal
resistance from junction to ambient (R
θ
JA
) is derived
from an EIA/JEDEC standard for measuring thermal
resistance for small surface mount packages. The EIA/
JEDEC specification is JESD51-7, “High Effective
Thermal Conductivity Test Board for Leaded Surface
Mount Packages”. The standard describes the test
method and board specifications for measuring the
thermal resistance from junction to ambient. The actual
thermal resistance for a particular application can vary
depending on many factors, such as copper area and
thickness. Refer to AN792, “A Method to Determine
How Much Power a SOT-23 Can Dissipate in an
Application”, (DS00792), for more information regarding
this subject.
Junction Temperature Estimate
To estimate the internal junction temperature, the
calculated temperature rise is added to the ambient or
offset temperature. For this example, the worst-case
junction temperature is estimated below.
Maximum Package Power Dissipation at +40°C
Ambient Temperature
6.4
Voltage Reference
The MCP1700 can be used not only as a regulator, but
also as a low quiescent current voltage reference. In
many microcontroller applications, the initial accuracy
of the reference can be calibrated using production test
equipment or by using a ratio measurement. When the
initial accuracy is calibrated, the thermal stability and
line regulation tolerance are the only errors introduced
by the MCP1700 LDO. The low cost, low quiescent
current and small ceramic output capacitor are all
advantages when using the MCP1700 as a voltage
reference.
FIGURE 6-2:
voltage reference.
Using the MCP1700 as a
6.5
Pulsed Load Applications
For some applications, there are pulsed load current
events that may exceed the specified 250 mA
maximum specification of the MCP1700. The internal
current limit of the MCP1700 will prevent high peak
load demands from causing non-recoverable damage.
The 250 mA rating is a maximum average continuous
rating. As long as the average current does not exceed
250 mA, pulsed higher load currents can be applied to
the MCP1700
.
The typical current limit for the
MCP1700 is 550 mA (T
A
+25°C).
Package
Package Type = SOT-23
Input Voltage
V
IN
= 2.3V to 3.2V
LDO Output Voltages and Currents
V
OUT
= 1.8V
I
OUT
= 150 mA
Maximum Ambient Temperature
T
A(MAX)
= +40°C
Internal Power Dissipation
Internal Power dissipation is the product of the LDO
output current times the voltage across the LDO
(V
IN
to V
OUT
).
P
LDO(MAX)
= (V
IN(MAX)
- V
OUT(MIN)
) x I
OUT(MAX)
P
LDO
= (3.2V - (0.97 x 1.8V)) x 150 mA
P
LDO
= 218.1 milli-Watts
T
J(RISE)
= P
TOTAL
x Rq
JA
T
JRISE
= 218.1 milli-Watts x 230.0
°
C/Watt
T
JRISE
= 50.2
°
C
T
J
= T
JRISE
+ T
A(MAX)
T
J
= 90.2°C
SOT-23 (230.0°C/Watt = R
θ
JA
)
P
D(MAX)
= (125°C - 40°C) / 230°C/W
P
D(MAX)
= 369.6 milli-Watts
SOT-89 (52°C/Watt = R
θ
JA
)
P
D(MAX)
= (125°C - 40°C) / 52°C/W
P
D(MAX)
= 1.635 Watts
TO-92 (131.9°C/Watt = R
θ
JA
)
P
D(MAX)
= (125°C - 40°C) / 131.9°C/W
P
D(MAX)
= 644 milli-Watts
PIC
MCP1700
V
IN
V
OUT
GND
C
IN
1 μF
C
OUT
1 μF
Bridge Sensor
V
REF
ADO
AD1
Ratio Metric Reference
1 μA Bias
Microcontroller
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