Datasheet LTC3877 (Analog Devices)

LTC3877 Dual Phase Step-Down Synchronous Controller with VID Output Voltage Programming and Low Value DCR Sensing
FeaTures DescripTion
n
6-Bit Parallel VID (Voltage Identification) Inputs Set
The LTC®3877 is a VID-programmable, constant frequency
Output Voltage from 0.6V to 1.23V in 10mV Steps
current mode step-down controller using an advanced and n
Output Voltage Range: 0.6V to 5V (Without VID)
proprietary architecture. This new architecture enhances n
Ultra Low Value DCR/R
the signal-to-noise ratio of the current sense signal, al-
SENSE Current Sensing
n
±1% Maximum Total Regulation Voltage Accuracy
lowing the use of very low DC resistance power inductors
Over Temperature
to maximize efficiency in high current applications. This n
Dual Differential Remote Sensing Amplifiers
feature also dramatically reduces the current sensing error, n
t
so that current sharing is greatly improved in multi-phase
ON(MIN) = 40ns, Capable of Very Low Duty Cycles at
low DCR applications. In addition, the controller achieves a
High Frequency
n minimum on-time of just 40ns, permitting the use of high
Phase-Lockable Frequency from 250kHz to 1MHz
n switching frequency at high step-down ratios.
Current Mismatch Between Channels: 5% Max
n Adjustable Soft-Start Current Ramping or Tracking The LTC3877 features dual high speed remote sense dif- n Multi-IC Operation Up To 12 Phases ferential amplifiers, programmable current sense limits n Wide VIN Range: 4.5V to 38V and DCR temperature compensation to limit the maximum n Dual Power Good Output Voltage Monitors output current precisely over temperature. The LTC3877 n Output Overvoltage Protection also features a precise 0.6V reference with guaranteed n Foldback Output Current Limiting and Soft Recovery accuracy of ±0.5%. The LTC3877 is available in a low profile 44-lead 7mm × 7mm QFN package.
applicaTions
L, LT, LTC, LTM, Burst Mode, OPTI-LOOP, PolyPhase, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the n FPGAs and Processor Power property of their respective owners. Protected by U.S. Patents including 5481178, 5705919, 5929620, 6100678, 6144194, 6177787, 6304066, 6580258. n Servers and Computing
Typical applicaTion High Efficiency Dual Phase Single Output, 400kHz, 0.9V/60A Step-Down Converter Efficiency and Power Loss
VIN
vs Load Current
6V TO 20V + 10µF INTVCC 270µF ×4 V FROM IN INTVCC CHL_SEL 4.7µF 34.8k µP 100 10 PINS NOT SHOWN 12V VIN IN THIS CIRCUIT: RUN VID_EN 400kHz 9 CLKOUT 95 CCM 10k VID1,2,3,4 8 EXTVCC I EFFICIENCY PGOOD1 LIM MODE/PLLIN 7 PGOOD2 90 TG1 TG2 PHASMD 0.1µF LTC3877 0.1µF 6 ITEMP 0.25µH 0.25µH BOOST1 BOOST2 85 5 (0.32mΩ DCR) (0.32mΩ DCR) SW1 SW2 4 EFFICIENCY (%) POWER LOSS 80 BG1 BG2 3 VOUT = 1.2V GND 75 2 VOUT = 0.9V 715Ω 715Ω VOUT = 1.2V 1 SNSA1+ SNSA2+ V 220nF 220nF OUT = 0.9V 70 0 SNS1– SNS2– 0 10 20 30 40 50 60 3.57k 220nF 220nF 3.57k LOAD CURRENT (A) SNSD1+ SNSD2+ VOUT VOUT V + 0.9V 3877 TA01b FB2 V + 60A 100µF FB1 VOSNS1 100µF 10k – ×2 DIFFOUT VOSNS1 ×2 + V – I FB2 TH1 + 330µF 330µF 20k FREQ ITH2 ×3 ×3 TK/SS1 TK/SS2 VID 1.5nF 0,5 86.6k 8.45k 0.1µF 3877 TA01 3877f For more information www.linear.com/LTC3877 1