參數(shù)資料
型號(hào): LT1578IS8-2.5
廠商: LINEAR TECHNOLOGY CORP
元件分類: 穩(wěn)壓器
英文描述: RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS
中文描述: SWITCHING REGULATOR, 240 kHz SWITCHING FREQ-MAX, PDSO8
封裝: 0.150 INCH, PLASTIC, SO-8
文件頁(yè)數(shù): 20/28頁(yè)
文件大?。?/td> 286K
代理商: LT1578IS8-2.5
20
LT1578/LT1578-2.5
APPLICATIO
S I
FOR
ATIO
U
the output. Gain is set by the 1.5A/V transconductance of
the LT1578 power section and the effective complex
impedance from output to ground. Gain rolls off smoothly
above the 160Hz pole frequency set by the 100
μ
F output
capacitor. Phase drop is limited to about 85
°
. Phase
recovers and gain levels off at the zero frequency (
16kHz)
set by capacitor ESR (0.1
).
Error amplifier transconductance phase and gain are shown
in Figure 11. The error amplifier can be modeled as a
transconductance of 1000
μ
Mho, with an output imped-
ance of 570k
in parallel with 2.4pF. In all practical
applications, the compensation network from the V
C
pin to
ground has a much lower impedance than the output
impedance of the amplifier at frequencies above 200Hz.
W
U
U
This means that the error amplifier characteristics them-
selves do not contribute excess phase shift to the loop, and
the phase/gain characteristics of the error amplifier sec-
tion are completely controlled by the external compensa-
tion network.
In Figure 12, full loop phase/gain characteristics are
shown with a compensation capacitor of 100pF, giving the
error amplifier a pole at 2.8kHz, with phase rolling off to
90
°
and staying there. The overall loop has a gain of 66dB
at low frequency, rolling off to unity-gain at 58kHz. The
phase plot shows a two-pole characteristic until the ESR
of the output capacitor brings it back to single pole above
16kHz. Phase margin is about 77
°
at unity-gain.
FREQUENCY (Hz)
G
μ
M
P
2000
1500
1000
500
0
–500
200
150
100
50
0
–50
10
1k
10k
1M
1578 F11
100
100k
GAIN
PHASE
R
570k
C
2.4pF
V
C
ERROR AMPLIFIER EQUIVALENT CIRCUIT
R
LOAD
= 50
V
FB
1
×
10
–3
)
(
+
1.21V
V
SW
V
C
LT1578
GND
1578 F09
R1
OUTPUT
ESR
C
F
C
C
R
C
ERROR
AMPLIFIER
FB
R2
C1
CURRENT MODE
POWER STAGE
g
m
= 1.5A/V
+
Figure 10. Response from V
C
Pin to Output
FREQUENCY (Hz)
10
G
P
40
20
0
–20
–40
40
0
–40
–80
–120
100
1k
1578 F07
10k
100k
GAIN
PHASE
V
IN
= 10V
V
OUT
= 5V
I
OUT
= 500mA
Figure 12. Overall Loop Characteristics
FREQUENCY (Hz)
L
L
80
60
40
20
0
–20
180
135
90
45
0
–45
10
1k
10k
1M
1578 F12
100
100k
V
IN
= 10V
V
OUT
= 5V
I
OUT
= 500mA
C
= 100
μ
F
10V, AVX TPS
C
= 100pF
L = 30
μ
H
PHASE
GAIN
Figure 9. Model for Loop Response
Figure 11. Error Amplifier Gain and Phase
相關(guān)PDF資料
PDF描述
LT1578C CAP 22UF 50V ELECT TG SMD
LT1578CS8 CAP 47UF 50V ELECT TG SMD
LT1578CS8-2.5 CAP 10UF 63V ELECT TG SMD
LT1578I CAP 22UF 63V ELECT TG SMD
LT1578 1.5A, 200kHz Step-Down Switching Regulator(1.5A, 200kHz,步降開(kāi)關(guān)穩(wěn)壓器)
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