POWER LOSS (mW)
LTC3891
Low I , 60V Synchronous
Q
Step-Down Controller
FEATURES DESCRIPTION
n
Wide V Range: 4V to 60V (65V Abs Max)
The LTC 3891 is a high performance step-down switching
IN
n
Low Operating I : 50A
regulator DC/DC controller that drives an all N-channel
Q
n
Wide Output Voltage Range: 0.8V V 24V
synchronous power MOSFET stage. A constant fre-
OUT
n
R or DCR Current Sensing
quency current mode architecture allows a phase-lockable
SENSE
n
Phase-Lockable Frequency (75kHz to 750kHz)
frequency of up to 750kHz.
n
Programmable Fixed Frequency (50kHz to 900kHz)
The 50A no-load quiescent current extends operating run
n
Selectable Continuous, Pulse-Skipping or Low Ripple
time in battery-powered systems. OPTI-LOOP compensa-
Burst Mode Operation at Light Load
tion allows the transient response to be optimized over
n
Selectable Current Limit
a wide range of output capacitance and ESR values. The
n
Very Low Dropout Operation: 99% Duty Cycle
LTC3891 features a precision 0.8V reference and power
n
Adjustable Output Voltage Soft-Start or Tracking
good output indicator. A wide 4V to 60V input supply range
n
Power Good Output Voltage Monitor
encompasses a wide range of intermediate bus voltages
n
Output Overvoltage Protection
and battery chemistries. The output voltage of the LTC3891
n
Low Shutdown I : < 14A
Q
can be programmed between 0.8V to 24V.
n
Internal LDO Powers Gate Drive from V or EXTV
IN CC
n
The TRACK/SS pin ramps the output voltages during
No Current Foldback During Start-Up
n
start-up. Current foldback limits MOSFET heat dissipation
Small 20-Pin 3mm 4mm QFN and TSSOP Packages
during short-circuit conditions. The PLLIN/MODE pin se-
lects among Burst Mode operation, pulse-skipping mode,
APPLICATIONS
or continuous conduction mode at light loads.
n L, LT, LTC, LTM, OPTI-LOOP, Burst Mode, Linear Technology and the Linear logo are registered
Automotive Always-On Systems
trademarks of Linear Technology Corporation. All other trademarks are the property of their
n
Battery Powered Digital Devices respective owners. Patents, including 5481178, 5705919, 6611131, 6498466, 6580258,
7230497.
n
Distributed DC Power Systems
TYPICAL APPLICATION
Efficiency and Power Loss vs
High Efficiency 3.3V Step-Down Converter
Output Current
V
IN
100 10000
4V TO 60V
V = 12V
IN
22F V = 3.3V
90 OUT
V INTV
IN CC
LTC3891
1000
80
2.2F
70
TG
100
41.2k 60
FREQ
0.1F
50
BOOST
2200pF
4.7H
10k 8m
V
OUT 10
40
ITH
SW
3.3V
100pF
30
5A
150F
BG
20 1
0.1F
+ 10
TRACK/SS SENSE
0.1
0
0.0001 0.001 0.01 0.1 1 10
100k
SENSE
OUTPUT CURRENT (A)
SGND
V
3891 TA01b
FB
100k
PGOOD INTV
CC 31.6k
3891 TA01a
3891fa
1
EFFICIENCY (%)LTC3891
ABSOLUTE MAXIMUM RATINGS
(Note 1)
ITH, V Voltages ......................................... 0.3V to 6V
Input Supply Voltage (V ) ......................... 0.3V to 65V
IN FB
PGOOD Voltage ............................................ 0.3V to 6V
Topside Driver Voltage (BOOST) .................0.3V to 71V
TRACK/SS Voltage ....................................... 0.3V to 6V
Switch Voltage (SW) ..................................... 5V to 65V
Operating Junction Temperature Range (Notes 2, 3)
(BOOST-SW) ................................................ 0.3V to 6V
LTC3891E, LTC3891I .......................... 40C to 125C
RUN ............................................................. 0.3V to 8V
LTC3891H .......................................... 40C to 150C
Maximum Current Sourced into Pin from
LTC3891MP ....................................... 55C to 150C
Source > 8V ......................................................100A
+
Maximum Junction Temperature (Notes 2, 3)
SENSE , SENSE Voltages ......................... 0.3V to 28V
LTC3891E, LTC3891I ......................................... 125C
PLLIN/MODE, INTV Voltages ................... 0.3V to 6V
CC
LTC3891H, LTC3891MP .................................... 150C
I , FREQ Voltages ..............................0.3V to INTV
LIM CC
Storage Temperature Range .................. 65C to 150C
EXTV ...................................................... 0.3V to 14V
CC
PIN CONFIGURATION
TOP VIEW
TOP VIEW
TRACK/SS 1 20 I
LIM
20 19 18 17 FREQ 2 19 V
IN
PLLIN/MODE 3 18 PGND
PLLIN/MODE 1 16 PGND
SGND 4 17 EXTV
SGND 2 15 EXTV
CC CC
SGND 3 14 INTV SGND 5
21 16 INTV
21 CC CC
SGND SGND
RUN 4 13 BG
RUN 6 15 BG
BOOST
SENSE 5 12
SENSE 7 14 BOOST
+
SENSE 6 11 SW +
SENSE 8 13 SW
7 8 9 10
V 9 TG
12
FB
ITH 10 11 PGOOD
FE PACKAGE
20-LEAD PLASTIC TSSOP
UDC PACKAGE
20-LEAD (3mm 4mm) PLASTIC QFN
T = 150C, = 38C/W
JMAX JA
EXPOSED PAD (PIN 21) IS SGND, MUST BE SOLDERED TO PCB
T = 150C, = 43C/W
JMAX JA
EXPOSED PAD (PIN 21) IS SGND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LTC3891EUDC#PBF LTC3891EUDC#TRPBF LFXV 20-Lead (3mm 4mm) Plastic QFN 40C to 125C
LTC3891IUDC#PBF LTC3891IUDC#TRPBF LFXV 20-Lead (3mm 4mm) Plastic QFN 40C to 125C
LTC3891HUDC#PBF LTC3891HUDC#TRPBF LFXV 20-Lead (3mm 4mm) Plastic QFN 40C to 150C
LTC3891MPUDC#PBF LTC3891MPUDC#TRPBF LFXV 20-Lead (3mm 4mm) Plastic QFN 55C to 150C
3891fa
2
V FREQ
FB
TRACK/SS
ITH
PGOOD I
LIM
TG V
IN