參數(shù)資料
型號: MC33263NW-30R2
廠商: ON SEMICONDUCTOR
元件分類: 基準(zhǔn)電壓源/電流源
英文描述: Ultra Low Noise 150 mA Low Dropout Voltage Regulator with ON/OFF Control
中文描述: 3 V FIXED POSITIVE LDO REGULATOR, 0.26 V DROPOUT, PDSO6
封裝: SOT-23L, 6 PIN
文件頁數(shù): 6/12頁
文件大?。?/td> 269K
代理商: MC33263NW-30R2
MC33263
http://onsemi.com
6
MC33263 Wake–up Improvement
– In portable
applications, an immediate response to an enable signal is
vital. If noise is not of concern, the MC33263 without a
bypass capacitor settles in nearly 20 s and typically delivers
65 VRMS between 100 Hz and 100 kHz.
In ultra low–noise systems, the designer needs a 10 nF
bypass capacitor to decrease the noise down to 25 VRMS
between 100 Hz and 100 kHz. With the adjunction of the
10 nF capacitor, the wake–up time expands up to 1 ms as
shown on the data–sheet curves. If an immediate response
is wanted, following figure’s circuit gives a solution to
charge the bypass capacitor with the enable signal without
degrading the noise response of the MC33263.
At power–on, C4 is discharged. When the control logic
sends its wake–up signal by going to a high level, the PNP
base is momentarily tight to ground. The PNP switch closes
and immediately charges the bypass capacitor C1 toward its
operating value. After a few s, the PNP opens and becomes
totally transparent to the regulator.
This circuit improves the response time of the regulator
which drops from 1 ms down to 30 s. The value of C4 needs
to be tweaked in order to avoid any bypass capacitor
overload during the wake–up transient.
Figure 4. A PNP Transistor Drives the
Bypass Pin when Enable Goes High
6
5
4
1
2
3
MC33263
+
+
C2
1.0 F
C3
1.0 F
Input
Output
C4
470 pF
C1
10 nF
R2
220 k
MMBT2902LT1
Q1
On/Off
Figure 5. MC33263 Wake–up Improvement with Small PNP Transistor
MC33263 Without
Wake–up Improvement
(Typical Response)
MC33263 With
Wake–up Improvement
(Typical Response)
1 ms
30 s
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