LTC3831-1 Datasheet, PDF (1/20 Pages) Linear Technology – High Power Synchronous Switching Regulator Controller for DDR Memory Termination

FEATURES
s _{VOUT as Low as 0.4V}
s _{High Power Switching Regulator Controller}
for DDR Memory Termination
s _{VOUT Tracks 1/2 of VIN or External VREF}
s _{No Current Sense Resistor Required}
s _{Low VCC Supply: 3V to 8V}
s _{Maximum Duty Cycle > 91% Over Temperature}
s _{Drives All N-Channel External MOSFETs}
s _{High Efficiency: Up to 95%}
s _{Programmable Fixed Frequency Operation:}
100kHz to 500kHz
s _{External Clock Synchronization Operation}
s _{Programmable Soft-Start}
s _{Low Shutdown Current: <10µA}
s _{Overtemperature Protection}
s _{Available in 16-PUin Narrow SSOP Package}
APPLICATIO S
s _{DDR SDRAM Termination}
s _{SSTL_2, SSTL_3 Interface}
s _{HSTL Interface}
LTC3831-1
High Power Synchronous
Switching Regulator Controller
for DDR Memory Termination
DESCRIPTIO
The LTC^®3831-1 is a high power, high efficiency switch-
ing regulator controller designed for DDR memory termi-
nation. The LTC3831-1 generates an output voltage equal
to 1/2 of an external supply or reference voltage. The
LTC3831-1 uses a synchronous switching architecture
with N-channel MOSFETs. Additionally, the chip senses
output current through the drain-source resistance of the
upper N-channel FET, providing an adjustable current
limit without a current sense resistor.
The LTC3831-1 operates with input supply voltage as low
as 3V and with a maximum duty cycle of > 91%. It includes
a fixed frequency PWM oscillator for low output ripple
operation. The 300kHz free-running clock frequency can
be externally adjusted or synchronized with an external
signal from 100kHz to above 500kHz. In shutdown mode,
the LTC3831-1 supply current drops to <10µA.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
0.75V DDR Memory Termination Application
V_DDQ
1.5V
12V
3.3V ^4.7µF
2.2µF
0.01µF
PV_CC2
V_CC
PV_CC1
TG
SS
I_MAX
LTC3831-1 I_FB
FREQSET
BG
SHDN
SHDN
PGND
68pF _1k
COMP
GND
R⁺
22nF
R^–
FB
0.1µF
4.7k
1k
+
220µF
1.3µH
+
180µF
V_TT
(V_OUT)
0.75V
±10A
38311 TA01a
Efficiency vs Load Current
100
T_A = 25°C
90
80
70
V_DDQ = 1.8V
V_DDQ = 1.5V
60
50
40
30
20
10
0
0 1 2 3 4 5 6 7 8 9 10
LOAD CURRENT (A)
3831 TAO1b
38311f
1