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LTC3879IMSE#PBF

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P27P28-P28
LTC3879
1
3879f
TYPICAL APPLICATION
FEATURES
APPLICATIONS
DESCRIPTION
Fast, Wide Operating
Range No R
SENSE
Step-Down Controller
n
Distributed Power Systems
n
Embedded Computing
n
Communications Infrastructure
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
No R
SENSE
is a trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Protected by U.S. Patents, including 5481178, 6100678, 6580258, 5847554, 6304066.
n
Wide V
IN
Range: 4V to 38V
n
±1% 0.6V Voltage Reference
n
Extremely Fast Transient Response
n
t
ON(MIN)
: 43ns
n
No R
SENSE
™ Valley Current Mode Control
n
Stable with Low ESR Ceramic C
OUT
n
Supports Smooth Start-Up in Pre-Biased Output
n
Optimized for High Step-Down Ratios
n
Adjustable Output Voltage Soft-Start or Tracking
n
Power Good Output Voltage Monitor
n
Dual N-Channel MOSFET Synchronous Drive
n
Adjustable Switching Frequency
n
Programmable Current Limit with Foldback
n
Output Overvoltage Protection
n
16-Pin MSOP and 3mm × 3mm QFN Packages
The LTC
®
3879 is a synchronous step-down switching
regulator controller optimized for high switching frequency
and fast transient response. The constant on-time valley
current mode architecture allows for a wide input range,
including very low duty factor operation. No external sense
resistor or slope compensation is required. System fl ex-
ibility is offered through a user-programmable soft-start pin
and independent RUN pin. The voltage ramping soft-start
function can be programmed with a capacitor or made to
track an external reference source.
Operating frequency is set by an external resistor and
compensated for variations in V
IN
to offer excellent line
stability. Discontinuous mode operation provides high
effi ciency during light load conditions. A forced continu-
ous control pin allows the user to reduce noise and RF
interference. Safety features include output overvoltage
protection and programmable current limit with foldback.
The current limit is user programmable.
The LTC3879 allows operation from 4V to 38V at the input
and from 0.6V to 90% V
IN
at the output. The LTC3879 is
available in a small 16-pin thermally enhanced MSOP or
3mm × 3mm QFN packages.
High Effi ciency Step-Down Converter Effi ciency vs Load Current
I
ON
V
IN
TRACK/SS
RUN
I
TH
V
RNG
SGND
PGOOD
TG
BG
PGND
V
FB
SW
BOOST
MODE
INTV
CC
0.22μF
0.1μF
220pF
RJK0305
RJK0330
0.56μH
432k
27k
LTC3879
3879 TA01a
10k
10k
V
OUT
1.2V
15A
V
IN
4.5V TO 28V
4.7μF
330μF
s2
10μF
LOAD CURRENT (A)
30
EFFICIENCY (%)
90
100
20
10
80
50
70
60
40
0.01 1 10 100
3879 TA01b
0
0.1
CONTINUOUS
MODE
DISCONTINUOUS
MODE
V
IN
= 12V
V
OUT
= 1.2V
SW FREQ = 400kHz
FIGURE 10 CIRCUIT
LTC3879
2
3879f
ABSOLUTE MAXIMUM RATINGS
Input Supply Voltage (V
IN
) ......................... –0.3V to 40V
I
ON
Voltage ................................................. –0.3V to 40V
BOOST Voltage .......................................... –0.3V to 46V
SW Voltage ................................................... –5V to 40V
INTV
CC
, (BOOST-SW), TRACK/SS, RUN,
PGOOD Voltages .......................................... –0.3V to 6V
MODE, V
RNG
Voltages ................–0.3V to INTV
CC
+ 0.3V
(Note 1)
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LTC3879EMSE#PBF LTC3879EMSE#TRPBF 3879 16-Lead Plastic MSOP –40°C to 85°C (Note 4)
LTC3879IMSE#PBF LTC3879IMSE#TRPBF 3879 16-Lead Plastic MSOP –40°C to 85°C (Note 4)
LTC3879EUD#PBF LTC3879EUD#TRPBF LDTM
16-Lead (3mm × 3mm) Plastic QFN
–40°C to 85°C (Note 4)
LTC3879IUD#PBF LTC3879IUD#TRPBF LDTM
16-Lead (3mm × 3mm) Plastic QFN
–40°C to 85°C (Note 4)
Consult LTC Marketing for parts specifi ed with wider operating temperature ranges. *The temperature grade is identifi ed by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based fi nish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifi cations, go to: http://www.linear.com/tapeandreel/
V
FB
, I
TH
Voltages ....................................... –0.3V to 2.7V
Operating Temperature Range (Note 4)....–40°C to 85°C
Junction Temperature (Note 2) ............................. 125°C
Storage Temperature Range ...................–65°C to 150°C
Lead Temperature (Soldering, 10 sec)
MSOP Only ....................................................... 300°C
PIN CONFIGURATION
1
2
3
4
5
6
7
8
TRACK/SS
PGOOD
V
RNG
MODE
I
TH
SGND
I
ON
V
FB
16
15
14
13
12
11
10
9
BOOST
TG
SW
PGND
BG
INTV
CC
V
IN
RUN
TOP VIEW
17
MSE PACKAGE
16-LEAD PLASTIC MSOP
T
JMAX
= 125°C, θ
JA
= 40°C/W
EXPOSED PAD (PIN 17) IS SGND, MUST BE SOLDERED TO PCB
16 15 14 13
5 6 7 8
TOP VIEW
UD PACKAGE
16-LEAD (3mm s 3mm) PLASTIC QFN
9
10
11
12
4
3
2
1TRACK/SS
PGOOD
V
RNG
MODE
BG
INTV
CC
V
IN
RUN
BOOST
TG
SW
PGND
I
TH
SGND
I
ON
V
FB
17
T
JMAX
= 125°C, θ
JA
= 68°C/W, θ
JC
= 4.2°C/W
EXPOSED PAD (PIN 17) IS SGND, MUST BE SOLDERED TO PCB
LTC3879
3
3879f
ELECTRICAL CHARACTERISTICS
The l denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at T
A
= 25°C. V
IN
= 15V, unless otherwise noted.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Main Control Loop
Input Operating Voltage Range 4 38 V
I
Q
Input DC Supply Current
Normal
Shutdown Supply Current
1350
18
2000
35
μA
μA
V
FBREF
Feedback Reference Voltage I
TH
= 1.2V (Note 3)
l
0.594 0.6 0.606 V
Feedback Voltage Line Regulation V
IN
= 4V to 30V, I
TH
= 1.2V (Note 3) 0.005 %/V
Feedback Voltage Load Regulation I
TH
= 0.5V to 1.9V (Note 3)
l
–0.05 –0.3 %
I
FB
Feedback Input Current V
FB
= 0.6V –5 ±50 nA
g
m(EA)
Error Amplifi er Transconductance I
TH
= 1.2V (Note 3) 1.4 1.7 2 mS
V
MODE
MODE Threshold 0.76 0.8 0.84 V
MODE Pin Current V
MODE
= 0.8V 0 ±1 μA
t
ON
On-Time I
ON
= 30μA
I
ON
= 15μA
198
370
233
440
268
510
ns
ns
t
ON(MIN)
Minimum On-Time I
ON
= 180μA 43 75 ns
t
OFF(MIN)
Minimum Off-Time I
ON
= 30μA 220 300 ns
V
SENSE(MAX)
Valley Current Sense Threshold
V
PGND
– V
SW
Peak Current = Valley + Ripple
V
RNG
= 1V, V
FB
= 0.56V
V
RNG
= 0V, V
FB
= 0.56V
V
RNG
= INTV
CC
, V
FB
= 0.56V
l
l
l
108
22
62
133
30
75
165
48
98
mV
mV
mV
V
SENSE(MIN)
Minimum Current Sense Threshold
V
PGND
– V
SW
Force Continuous Operation
V
RNG
= 1V, V
FB
= 0.64V
V
RNG
= 0V, V
FB
= 0.64V
V
RNG
= INTV
CC
, V
FB
= 0.64V
–61
–12
–33
mV
mV
mV
V
RUN
RUN On Threshold V
RUN
Rising 1.3 1.5 1.7 V
I
RUN
RUN Pull-Up Current V
RUN
= 0V –1.2 μA
I
TRACK/SS
Soft-Start Charging Current V
TRACK/SS
= 0V –0.45 –1 –2 μA
INTV
CC
Undervoltage Lockout Falling
l
3.3 3.9 V
INTV
CC
Undervoltage Lockout Release Rising
l
3.6 4 V
TG Driver Pull-Up On-Resistance TG High 2.5 Ω
TG Driver Pull-Down On-Resistance TG Low 1.2 Ω
BG Driver Pull-Up On-Resistance BG High 2.5 Ω
BG Driver Pull-Down On-Resistance BG Low 0.7 Ω
TG Rise Time C
LOAD
= 3300pF (Note 5) 20 ns
TG Fall Time C
LOAD
= 3300pF (Note 5) 20 ns
BG Rise Time C
LOAD
= 3300pF (Note 5) 20 ns
BG Fall Time C
LOAD
= 3300pF (Note 5) 20 ns
Top Gate Off to Bottom Gate On Delay
Synchronous Switch-On Delay Time
C
LOAD
= 3300pF Each Driver (Note 5) 15 ns
Bottom Gate Off to Top Gate On Delay
Top Switch-On Delay Time
C
LOAD
= 3300pF Each Driver (Note 5) 15 ns
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LTC3879IMSE#PBF

Mfr. #:
Buy LTC3879IMSE#PBF
Manufacturer:
Analog Devices / Linear Technology
Description:
Switching Voltage Regulators Fast, Wide Operating Range No Rsense Step-Down Controller
Lifecycle:
New from this manufacturer.
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