BIPHASE CURRENT MODE
CONTROLLER
SC2422A
PRELIMINARY - August 7, 2000
TEL:805-498-2111 FAX:805-498-3804 WEB:http://www.semtech.com
DESCRIPTION
FEATURES
The SC2422A biphase, current mode controller is de-
signed to work with Semtech smart synchronous
drivers, such as the SC1205, SC1305 or the SC1405 to
provide the DC/DC converter solution for the most
demanding Micro-processor applications. Input current
rather than output current sensing is used to guarantee
precision phase to phase current matching using a
single sense resistor on the input power line. Accurate
current sharing and pulse by pulse current limit are
implemented without the power loss and transient re-
sponse degradation associated with output current
sense methods. Two phase operation allows significant
reduction in input/output ripple while enhancing tran-
sient response.
•
Precision, pulse by pulse phase current match-
ing
•
•
•
Active drooping allows for best transient response
Input Sensing Current mode control
Programmable DAC step size/offset allows
Compliance with VRM9.0, VRM8.3 or VRM8.4
Externally programmable soft-start
5V or 12V input for next generation processors
0% minimum duty cycle improves transient re-
sponse
Externally Programmable UVLO with hysteresis
Cycle by cycle current limiting
Programmable Internal Oscillator to 1 MHz
VID IIIII Inhibit (No CPU)
•
•
•
•
•
•
•
The DAC step size and range are programmable with
external components thus allowing compliance with
new and emerging VID ranges.
APPLICATIONS
•
•
•
Intel Advanced Microprocessors
AMD AthlonTM power supplies
A novel approach implements active droop, minimizing
output capacitor requirements during load transients.
This avoids the pitfalls of the passive droop implemen-
tation. This feature also allows easy implementation of
N+1 redundancy and current sharing among modules.
Servers/Workstations, high density power supplies
ORDERING INFORMATION
DEVICE(1)
SC2422ACS.TR
SC2422A.EVB
PACKAGE
TEMP. RANGE (TJ)
Programmable Under Voltage Lockout assures proper
start-up and shutdown by synchronizing the controller
to the driver supply. Wide PWM frequency range allows
use of low profile, surface mount components.
SO-16
0 - 125°C
Evaluation Board
Note:
(1) Only available in tape and reel packaging. A reel con-
tains 1000 devices.
TYPICAL APPLICATION SCHEMATIC
INPUT
Rsens
VIN
1
3
4
7
6
5
IN
DRVH
PHASE
DRVL
1
16
15
14
13
12
11
10
9
VID4
VID3
VID2
VID1
VID0
ERROUT
FB
VCC
BGOUT
OC+
VCC
VDD
2
3
4
5
6
7
8
SC1305
OUT1
OUT2
OC-
VIN
1
3
4
7
6
5
IN
DRVH
PHASE
DRVL
UVLO
GND
VCC
VDD
Rf
RREF
Rref
SC2422A
SC1305
Ri
Vout
1
© 2000 SEMTECH CORP.
652 MITCHELL ROAD NEWBURY PARK CA 91320