Sink and Source DC/DC Controller for
Termination Power Supply Applications
POWER MANAGEMENT
Description
The SC1110 is a low-cost, full featured, synchronous
voltage-mode controller designed to generate
termination voltage in double data rate (DDR) memory
systems and other applications where wide data bus
need to be actively terminated. Synchronous control of
the MOSFET half bridge allows power flowing
bi-directionally. The termination voltage can be tightly
regulated to track the chipset voltage, i.e. to be exactly
50% of that at all times.
The SC1110 is ideal for low cost implementation of
termination voltage supplies. SC1110 features include
temperature compensated voltage reference, triangle
wave oscillator and current sense comparator circuitry,
and allows the use of inexpensive N-channel power
MOSFETs.
The SC1110 operates at a fixed 250kHz, providing an
optimum compromise between efficiency, transient
performance, external component size, and cost.
SC1110
Features
Generates termination voltages for active termina-
tion schemes
1% set point accuracy
For ±7A output current, transient regulation is
better than ±80mV
V
REFIN
pin available for external 50% resistive divider
to allow termination voltage track of the chip set
voltage
Buffered V
REFOUT
for system usage
R
DSON
sensing for over current protection in hiccup
mode
Soft start and logic input enabling
250kHz switching for best transient and efficiency
performance
Gate drive capable for 0.5A sourcing and sinking
Applications
For DDR memory systems
For active termination schemes in high speed logic
systems
Typical Application Circuit
REFOUT
+5Vcc
+
R1
5k
C1
0.01
R2
1.24k
C2
0.1
R3
10
1
U1
SC1110
VCC
REFOUT
14
R4
1k
C4
0.022
C7
1.0
C8,9
2 x 10uF
C10,11
2 x 560uF
Vin 2.5V
_
SS/ENBL
2
C3
0.1
PWRGD
4
C25
0.1
PWRGD
COMP
11
SS/ENBL
REFIN
13
R5
1k
3
OCSET
SENSE
12
R6
4.7k
C5
0.047
5
GND
BSTL
10
D1
MBRM120
R7
2.2
R8
2.2
Q1
Si9426DY
Q2
Si9426DY
C6
1.0
6
PHASE
BSTH
9
7
DL
DH
8
L1
800 nH
+
C12-14
3 x 560uF
C15-24
10 x 10uF
Vout = 1.25V @ 7A
_
C10-14: Sanyo, 4SP560M
C8,9,15-24: TDK, CC3216AX5R0J106K
L1: Panasonic, ETQP6F0R8L or Falco, QPIP1205-809-3
Q1,Q2 options: Si9426DY, FDS6890A, IRF7401
D1: ON Semi (Motorola)
Revision: July 20, 2004
1
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