LTC3876_15 Datasheet, PDF (1/48 Pages) Linear Technology – Dual DC/DC Controller for DDR Power with Differential VDDQ Sensing and 50mA VTT Reference

LTC3876
FEATURES
Dual DC/DC Controller for
DDR Power with Differential VDDQ
Sensing and ±50mA VTT Reference
DESCRIPTION
n _{Complete DDR Power Solution with VTT Reference}
n _{Wide VIN Range: 4.5V to 38V, VDDQ: 1V to 2.5V}
n _{±0.67% VDDQ Output Voltage Accuracy}
n _{VDDQ and VTT Termination Controllers}
n _{±1.2% ±50mA Linear VTTR Reference Output}
n _{Controlled On-Time, Valley Current Mode Control}
n _{Frequency Programmable from 200kHz to 2MHz}
Synchronizable to External Clock
n _{tON(MIN) = 30ns, tOFF(MIN) = 90ns}
n _{RSENSE or Inductor DCR Current Sensing}
n _{Power Good Output Voltage Monitor}
n _{Overvoltage Protection and Current Limit Foldback}
n _{Thermally Enhanced 38-Pin (5mm × 7mm) QFN and}
TSSOP Packages
APPLICATIONS
n _{Motherboard Memory}
n _Servers
The LTC^®3876 is a complete DDR power solution, com-
patible with DDR1, DDR2, DDR3 and future DDRX lower
voltage standards. The LTC3876 includes VDDQ and VTT
DC/DC controllers and a precision linear VTT reference. A
differential output sense amplifier and precision internal
reference combine to offer an accurate VDDQ supply. The
VTT controller tracks the precision VTTR linear reference
with less than 20mV total DC error. The precision VTTR
reference maintains 1.2% regulation accuracy tracking one-
half VDDQ over temperature for a ±50mA reference load.
The LTC3876 allows operation from 4.5V to 38V maximum
at the input. The VDDQ output can range from 1.0V to
2.5V, with a corresponding VTT and VTTR output range
of 0.5V to 1.25V. Voltage tracking soft-start, PGOOD and
fault protection features are provided.
L, LT, LTC, LTM, Linear Technology, OPTI-LOOP, and the Linear logo are registered trademarks
and Hot Swap and No R_SENSE are trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners. Protected by U.S. Patents including
5481178, 5487554, 6580258, 6304066, 6476589, 6774611.
TYPICAL APPLICATION
DDR3 1.5V VDDQ/20A 0.75VTT/±10A 4.5V to 14V Input
V_IN
4.5V TO
14V
C_IN1
180μF
w2
1.5V, 20A
VDDQ
C_OUT1
100μF
0.1μF
15k
L1
0.47μH
3.57k
MT1
C_OUT2
330μF
w2
30.1k _MB1
20k
0.1μF
V_{IN LTC3876}
SENSE1^– SENSE2^–
SENSE1⁺ SENSE2⁺
BOOST1
BOOST2
TG1
TG2
DB1
1μF
4.7μF
SW1
DRV_CC1
INTV_CC
SW2
DRV_CC2
100k
BG1
BG2
PGND
V_OUTSENSE1+
V_{OUTSENSE1–} ^VTTRVCC
PGOOD _PGOOD
VTTSNS
0.1μF
TRACK/SS1
VTTR
15k 1000pF
ITH1
100k
ITH2
RT
SGND
RUN
3876 TA01a
0.1μF
DB2
1μF
1000pF
2.2μF
15k
0.1μF
15k
3.57k
MT2
L2
0.47μH
MB2
VTTR
±50mA
VTT
0.75V
±10A
C_OUT4
330μF
C_OUT3
100μF
Efficiency/Power Loss
VDDR Channel 1
100
4.5
V_IN = 12V
VDDQ = 1.5V
4.0
90
3.5
80 DISCONTINUOUS
3.0
MODE
2.5
70
2.0
60
1.5
50
40
0.1
1.0
FORCED
CONTINUOUS ^0.5
MODE
0
1
10
LOAD CURRENT (A)
3876 TA01b
3876f
1