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Número de pieza | SC4910B | |
Descripción | High Performance Secondary Side Controller | |
Fabricantes | Semtech Corporation | |
Logotipo | ||
Hay una vista previa y un enlace de descarga de SC4910B (archivo pdf) en la parte inferior de esta página. Total 19 Páginas | ||
No Preview Available ! SC4910A/B
High Performance Secondary Side
Controller with Synchronous Rectifier
POWER MANAGEMENT
Description
Features
The SC4910A/B is an integrated, full featured, second-
ary side controller designed for use in single ended and
isolated switch mode power supplies with synchronous
rectification where efficiency and fast transient response
are of primary concern. The SC4910A/B has outputs for
both primary FET and secondary synchronous rectifica-
tion. The primary drive output is designed to drive a small
and low cost pulse transformer to isolate the primary
FET driver. The secondary control makes it much easier
www.DatatSohemeto4Un.ictoomr and control the system load with tight control
loops and implement load current sharing and synchro-
nous rectification.
The SC4910A/B features synchronous rectification, multi-
phase link capability, programmable secondary side
delay, programmable switching frequency and program-
mable maximum duty cycle. It is designed for either
current mode or voltage mode operation.
Synchronous rectification with adaptive control
Programmable secondary side delay
Programmable switching frequency
Programmable max. duty cycle
Remote voltage sense capability
Close-loop soft start with active low shutdown
0.75V precision reference for low output applications
Oscillator sychronization
Undervoltage Lockout
Operation to 1MHz
Current-mode or voltage-mode operation
Single stage power conversion with multiphase link
capability (with SC4201)
Monotonic start-up with pre-biased output
Active current sharing capability
20 pin TSSOP package
Applications
The SC4910A has a typical turn-on threshold of 9V and
the SC4910B has a threshold of 4.5V.
Typical Application Circuit
Telecom isolated DC to DC converters
Isolated VRMS
Networking power supplies
Industrial power supplies
Distributed power architectures
High density power modules
+Vin
R2
C3
C1
D1
T1
M1
M2
L1
R1
C2
LOAD
SC1301
SC1301
SC1301
M3
T2
D2
R3
C9
D3
T3 C10
+12V
C4
SC4910
12 13 14
4
PVCC
CS
PVCC
AVCC 16
ISHARE
10
OUTA
PHASE 6
R4 20 RT1
OUTB 11
R5 19 RT2
COMP 17
3 SS
15 DELAY
5
VREF
AGND PGND
FB 18
2
SYNC/EN
-SENSE 1
PGND
C8 R9
7
89
C5
C6 R6
R7
R8
Revision: June 1, 2005
1
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1 page POWER MANAGEMENT
Pin Configurations
TOP VIEW
-SENSE
1
20 RT1
SYNC/EN
2
19 RT2
SS 3
18 FB
CS 4
17 COMP
VREF
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PHASE
5
6
16 ISHARE
15 DELAY
AGND
7
14 AVCC
PGND
8
13 PVCC
PGND
9
12 PVCC
OUTA
10
11
OUTB
(20 Pin TSSOP)
Marking Information
SC4910A/B
Ordering Information
Part Number
Package
SC4910AITSTRT(2)
SC4910BITSTRT(2)
TSSOP-20(1)
Notes:
(1) Only available in tape and reel packaging. A reel
contains 2500 devices.
(2) Lead free product. This product is fully WEEE and
RoHS compliant.
Part Number (Example: 1471)
yyww = Date Code (Example: 0012)
xxxxx = Semtech Lot No. (Example: P94A01)
Part Number (Example: 1471)
yyww = Date Code (Example: 0012)
xxxxx = Semtech Lot No. (Example: P94A01)
2005 Semtech Corp.
5
www.semtech.com
5 Page SC4910A/B
POWER MANAGEMENT
Applications Information (Cont.)
Type 2 compensator (Figure 3) is needed for the above
current mode control. The compensation network gives
the following characteristics:
1+ s
GCOMP
=
ω1
s
1+
ωz
s
ωp
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C3
R2 C1
R1
V ref
The goal of the compensation design is to shape the loop
with high DC gain, high bandwidth, enough phase margin,
and high attenuation for high frequency noises. Figure 4
gives the asymptotic diagrams of the power stage with
current loop closed and its loop gain.
One integrator is added to increase the DC gain. Wzc is
used
gain
htoasca–n2c0edl Btherapteowwehresntaitgerepaoclheewsp
so that the loop
0 dB line. wpc is
placed at output capacitor ESR or half switching frequency,
whichever is lower.
Arbitrarily choose R2, then
where
Figure 3
C1
=
1
R2ωP
,C3
=
C1
ωPC −
,R1
1
=
1
ωI(C1 + C3 )
ωZC
1
ω1 = R1(C1 + C3 )
1
ωZC = R2C1
1
ωPC
=
R2
C1C3
C1+C3
ωI is adjusted for satisfactory phase margin and
crossover frequency.
Synchronization
Synchronization of oscillators in multiphase operation
allows for reduced size of filtering components and
improved dynamic response.
The loop gain will be given by:
T = GvgGCOMPKFB
1+ s
=
Gvgo
1+
ωz
s
1+ s
•
ω1
s
1+
ωZC
s
•
Vref
VO
ωp ωPC
SC4910 provides single stage conversion where SC4201
provides the multiphase function. SC4910 and SC4201
are placed on the secondary side, outputs A and C of the
SC4201 are fed into the Sync pins of 2 separate
SC4910’s. Both power supplies operate 180 degrees
apart. SC4201 can be configured up to 4 phase
operation.
Loop gain T(s)
ωzc Power stage
Compensator
ωpc
ωP ωC
ωZ
Figure 4
fs
2005 Semtech Corp.
11
www.semtech.com
11 Page |
Páginas | Total 19 Páginas | |
PDF Descargar | [ Datasheet SC4910B.PDF ] |
Número de pieza | Descripción | Fabricantes |
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SC4910B | High Performance Secondary Side Controller | Semtech Corporation |
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