參數(shù)資料
型號(hào): MIC5190BMM TR
廠商: Micrel Inc
文件頁數(shù): 8/13頁
文件大?。?/td> 463K
描述: IC REG CTRLR SGL POS ADJ 10-MSOP
標(biāo)準(zhǔn)包裝: 2,500
類型: 正,可調(diào)式
輸出數(shù): 1
輸出電壓: 可調(diào)
電流 - 電源: 15mA
輸入電壓: 0.9 V ~ 5.5 V
工作溫度: -40°C ~ 125°C
封裝/外殼: 10-TFSOP,10-MSOP(0.118",3.00mm 寬)
供應(yīng)商設(shè)備封裝: 10-MSOP
包裝: 帶卷 (TR)
其它名稱: MIC5190BMMTR
MIC5190BMMTR-ND
MIC5190
Micrel
This places a pole at 2.3 kHz at 80dB and calculates as
follows.
F
M
pF
F
kHz
P
P
=
?/DIV>
?/DIV>
=
1
2    3 42
20
2 32
?nbsp   .
.
&
-20
0
20
40
60
80
100
0.01
0.1
1
10
100
1000   10000  100000
Frequency (KHz)
-45
0
45
90
135
180
225
Figure 4. Internal Compensation
Frequency Response
 There is single pole roll off. For most applications, an output
capacitor is required. The output capacitor and load resis-
tance create another pole. This causes a two-pole system
and can potentially cause design instability with inadequate
phase margin. External compensation is required. By provid-
ing a dominant pole and zeroallowing the output capacitor
and load to provide the final polea net single pole roll off is
created, with the zero canceling the dominant pole. Figure 5
demonstrates placing an external capacitor (C
COMP
) and
resistor (R
COMP
) for the external pole-zero combination.
Where the dominant pole can be calculated as follows:
Error Amplifier
Driver
3.42M&
20pF
Internal
External
Comp
R
COMP
C
COMP
Figure 5. External Compensation
F
M    C
P
COMP
=
?/DIV>
?/DIV>
1
2    3 42
?nbsp   .
&
And the zero can be calculated as follows:
F
R
C
Z
COMP
COMP
=
?/DIV>
?/DIV>
1
2?/DIV>
This allows for high DC gain, and high bandwidth with the
output capacitor and the load providing the final pole.
Figure 6. External Compensation
Frequency Response
It is recommended that the gain bandwidth should be de-
signed to be less than 1 MHz. This is because most capaci-
tors lose capacitance at high frequency and becoming resis-
tive or inductive. This can be difficult to compensate for and
can create high frequency ringing or worse, oscillations.
By increasing the amount of output capacitance, transient
response can be improved in multiple ways. First, the rate of
voltage drop vs. time is decreased. Also, by increasing the
output capacitor, the pole formed by the load and the output
capacitor decreases in frequency. This allows for the increas-
ing of the compensation resistor, creating a higher mid-band
gain.
Figure 7. Increasing Output Capacitance
This will have the effect of both decreasing the voltage drop
as well as returning closer and faster to the regulated voltage
during the recovery time.
MOSFET Selection
The typical pass element for the MIC5190 is an N-Channel
MOSFET. There are multiple considerations when choosing
a MOSFET. These include:
"  V
IN
 to V
OUT
 differential
"  Output current
"  Case size/thermal characteristics
"  Gate capacitance (C
ISS
<10nF)
"  Gate to source threshold
-20
0
20
40
60
80
100
0.01
0.1
1
10
100
1000   10000  100000
Frequency (KHz)
-45
0
45
90
135
180
225
The Dominant Pole
External Zero
R
LOAD
 ?/SPAN> C
OUT
Pole
C
comp
M
Fp
?
 
?
=
42
.
3
2
1
 
C
comp
R
comp
Fz
 ?/DIV>
?
=
 
2
1
-20
0
20
40
60
80
100
0.01
0.1
1
10
100
1000   10000  100000
Frequency (KHz)
-45
0
45
90
135
180
225
Increasing C
OUT 
reduces
the load resistance and
output capacitor pole
allowing for an increase
in mid-band gain.
December 2005
8
M9999-120105
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