- 您現(xiàn)在的位置：買賣IC網 > PDF目錄375321 > AN734 (Vishay Intertechnology,Inc.) Design Guidelines for the Low-Noise Low-Dropout Regulator Si9181 PDF資料下載
參數資料
| 型號： | AN734 |
| 廠商： | Vishay Intertechnology,Inc. |
| 英文描述： | Design Guidelines for the Low-Noise Low-Dropout Regulator Si9181 |
| 中文描述： | 為設計準則低噪聲低壓差穩(wěn)壓器Si9181 |
| 文件頁數： | 4/5頁 |
| 文件大?。?/td> | 47K |
| 代理商： | AN734 |
AN734
Vishay Siliconix
www.vishay.com
4
Document Number: 71337
31-Oct-00
–
60
–
40
–
20
0
20
40
60
100
1000
10000
100000
1000000
–
180
–
120
–
60
0
60
120
180
FIGURE 4.
Closed Loop Bandwidth
Frequency (Hz)
G
Phase
P
Gain
FIGURE 5.
Programmed Delay for Error
Signal
CH1
–
V
(Pin 5)
CH2
–
Error (Pin 7)
CH3
–
V
IN
(Pin 4)
CH4
–
C
(Pin 2)
C
DELAY
= 0.1 F
C
IN
= 2.2 F, C
OUT
= 2.2 F, I
LOAD
= 150 mA
2V/div
2V/div
2V/div
2V/div
ERROR SIGNAL WITH PROGRAMMABLE DELAY
The Si9181 is provided with an ERROR pin which can be used
as a high-going enable or power-good signal to activate the
electronic equipment once the output is within 5% of the set
value. When output voltage drops below 95% of its set level,
the ERROR pin can positively disable the electronics before
the low-going supply cripples the circuit. The ERROR signal
required to wake up the electronics can also be delayed with
respect to the output by adding a small capacitor at C
DELAY
(pin 2). The ERROR output is a high slew
–
rate open drain and
needs an external pull-up resistor.
The C
DELAY
capacitor is fully discharged through U2 when the
circuit is OFF or when the output is below the set power-good
threshold (0.95 V
OUT
). (See Figure 1.) Once the output goes
above the power-good trip threshold, the U2 output switches to
a high impedance state and C
DELAY
charges with a 2.2- A
(typ) constant current. U3 switches Q2 off at 1.215 V across
the C
DELAY
capacitor and the ERROR output is pulled high by
R
EXT
(Figure 5).
C
DELAY
1.81
10
6
t
DELAY
(7)
SHUTDOWN
The Si9181 is provided with an ON/OFF control pin (named
SD) that opens and closes the internal power MOSFET switch
and controls the total current drawn by the entire circuit. The
current is less than 1 A, reducing the drain on the battery in
standby mode and increasing standby time. While a low at the
SD pin opens the switch, a high at the SD pin enables the regu-
lator operation. This allows the Si9181 to be used as a high-
current simple disconnect switch that works in conjunction with
the regulated output. It is recommended that the user connect
the SD to the input V
IN
when not in use.
INPUT/OUTPUT CAPACITOR SELECTION
The circuit stability and output voltage during line and load step
changes dominate the selection criteria of input and output ca-
pacitors. A higher step load current at the output demands
higher capacitance with a lower ESR value at the output. An
input bypass capacitor is required in applications involving
long traces between the source and LDO. The input capacitor
should be at least equal to or greater than the output capacitor
for proper operation. A 2.2- F to 10- F ceramic capacitor with
a Y5V dielectric is recommended, and an X5R dielectric is rec-
ommended for better temperature characteristics. The Si9181
requires only a small output capacitor because of the high
closed loop bandwidth of 100 kHz or more. Also, the freedom
to use a very low
–
ESR ceramic capacitor reduces the form
factor further for greater performance.
V
I
STEP
t
RESPONSE
C
OUT
I
STEP
ESR
(8)
where:
I
STEP
= Output load step (A)
ESR = ESR of Output capacitor (W)
t
RESPONSE
= Response time of the regulator (s)
t
RESPONSE depends on the unity gain bandwidth and the phase
margin of the closed loop.
相關PDF資料 |
PDF描述 |
|---|---|
| AN7352 | Playback Pre-amplifier for Stereo Cassette Deck |
| AN7352S | Playback Pre-amplifier for Stereo Cassette Deck |
| AN7354 | WIRE, 18 GA, WHT, STRD, UL1015, 105C |
| AN7354SC | CABLE ASSEMBLY; SMA MALE TO SMA MALE RIGHT ANGLE; 50 OHM, RG401/U (.250" BARE COPPER); 6" CABLE LENGTH; ; **SEMI-RIGID CABLE, PLEASE LIMIT CUSTOM LENGTHS TO 60 INCHES OR LESS!! ** |
| AN7356NSC | Recording and playback equalizer amp. IC for Hi-Fi cassette deck |
相關代理商/技術參數 |
參數描述 |
|---|---|
| AN7345K | 制造商:Panasonic Industrial Company 功能描述:IC |
| AN7348K | 制造商:Panasonic Industrial Company 功能描述:IC |
| AN735014 | 制造商: 功能描述: 制造商:undefined 功能描述: |
| AN735-12 | 制造商:AN# - MILITARY 功能描述: |
| AN735-14 | 制造商:AN# - MILITARY 功能描述: |
發(fā)布緊急采購，3分鐘左右您將得到回復。