LT1576CS8-SYNC#TRPBF Linear Technology, LT1576CS8-SYNC#TRPBF Datasheet - Page 20
![IC SW REG STEP-DOWN 200KHZ 8SOIC](/photos/7/57/75766/lt1576cs8_sml.jpg)
LT1576CS8-SYNC#TRPBF
Manufacturer Part Number
LT1576CS8-SYNC#TRPBF
Description
IC SW REG STEP-DOWN 200KHZ 8SOIC
Manufacturer
Linear Technology
Type
Step-Down (Buck)r
Datasheet
1.LT1576CS8PBF.pdf
(28 pages)
Specifications of LT1576CS8-SYNC#TRPBF
Internal Switch(s)
Yes
Synchronous Rectifier
No
Number Of Outputs
1
Voltage - Output
Adj to 1.2V
Current - Output
1.5A
Frequency - Switching
200kHz
Voltage - Input
5 ~ 25 V
Operating Temperature
0°C ~ 125°C
Mounting Type
Surface Mount
Package / Case
8-SOIC (3.9mm Width)
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Power - Output
-
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Part Number:
LT1576CS8-SYNC#TRPBFLT1576CS8-SYNC#PBF
Manufacturer:
LINEAR/凌特
Quantity:
20 000
LT1576/LT1576-5
APPLICATIONS
the output. Gain is set by the 1.5A/V transconductance of
the LT1576 power section and the effective complex
impedance from output to ground. Gain rolls off smoothly
above the 160Hz pole frequency set by the 100 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 Mho, with an output imped-
ance of 570k
applications, the compensation network from V
ground has a much lower impedance than the output
impedance of the amplifier at frequencies above 200Hz.
20
LT1576
GND
CURRENT MODE
POWER STAGE
C
Figure 10. Response from V
g
–20
–40
F
m
40
20
0
= 1.5A/V
Figure 9. Model for Loop Response
10
V
R
C
C
C
C
in parallel with 2.4pF. In all practical
U
100
PHASE
AMPLIFIER
FREQUENCY (Hz)
ERROR
–
+
INFORMATION
U
GAIN
1k
1.21V
V
SW
FB
V
V
I
OUT
C
IN
OUT
10k
W
Pin to Output
= 10V
= 500mA
= 5V
1576 F07
100k
R1
R2
40
0
–40
–80
–120
+
U
ESR
C
C1
pin to
OUTPUT
1576 F09
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. Phase
shows a two-pole characteristic until the ESR of the output
capacitor brings it back above 16kHz. Phase margin is
about 77 at unity-gain.
–500
2000
1500
1000
Figure 11. Error Amplifier Gain and Phase
500
–20
80
60
40
20
Figure 12. Overall Loop Characteristics
0
0
10
10
V
R
V
V
I
C
10V, AVX TPS
C
L = 30 H
ERROR AMPLIFIER EQUIVALENT CIRCUIT
OUT
FB 1 10
IN
OUT
OUT
C
LOAD
= 100pF
= 10V
= 500mA
100
= 5V
= 100 F
100
= 50
–3
FREQUENCY (Hz)
FREQUENCY (Hz)
PHASE
GAIN
1k
1k
R
570k
OUT
10k
10k
PHASE
GAIN
100k
100k
C
2.4pF
OUT
V
C
1576 F11
1576 F12
1M
1M
200
150
100
50
0
–50
180
135
90
45
0
–45