SC4809A_16 Datasheet, PDF (1/16 Pages) Semtech Corporation – High Performance Current Mode PWM Controller

POWER MANAGEMENT
Description
The SC4809A/B/C is a 10 pin BICMOS primary side
current mode controller for use in Isolated DC-DC and
off-line switching power supplies. It is a highly integrated
solution, requiring few external components. It features
a high frequency of operation, accurately programmable
maximum duty cycle, current mode control, line voltage
monitoring, supply UVLO, low start-up current, and
programmable soft start with user accessible reference.
It operates in a fixed frequency, highly desirable for
Telecom applications. Features a separate sync pin which
simplifies synchronization to an external clock. Feeding
the oscillator of one device to the sync of another forces
biphase operation which reduces input ripple and filter
size.
The SC4809A/B/C have different threshold and VREF
to accommodate a wide variety of applications.
These devices are available in the MSOP–10 lead free
package.
SC4809A/B/C
High Performance Current Mode
PWM Controller
Features
‹ Operation to 1MHz
‹ Accurate programmable maximum duty cycle
‹ Line voltage monitoring
‹ External frequency synchronization
‹ Bi-phase mode of operation for low ripple
‹ Under 100µA start-up current
‹ Accessible reference voltage
‹ VDD undervoltage lockout
‹ -40°C to 105°C operating temperature
‹ 10 lead MSOP package. Lead free package available.
Fully WEEE and RoHS compliant
Applications
‹ Telecom equipment and power supplies
‹ Networking power supplies
‹ Power over LAN applications
‹ Industrial power supplies
‹ Isolated power supplies
Typical Application Circuit
+48V
C1
R1
R2
U1
SC4809
C7
1 _VDD
VREF ¹⁰
R3
2 _LUVLO
OUT ⁹
SYNC
3 _SYNC
GND ⁸
4 _RCT
FB ⁷
5 _DMAX
SS ⁶
R4
R5
-- 48V
R6 R7
C3
R8
Q1
C2
C4 C5 C6
DISABLE
T1
D1
U2
SC1301
1 _IN
EN ⁵
Q2
2 _GND
OUT ⁴
3 _VCC
R9
R10
R11
D2
C8
Vout
R12
R13
U3
U4
SC4431
C9
R14
Revision: September 21, 2005
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