ing regulator controller that drives an all N-channel synchro-
nous power MOSFET stage. A constant-frequency current
mode architecture allows a phase-lockable frequency of
up to 650kHz.
The 80μA no-load quiescent current extends operating
life in battery powered systems. OPTI-LOOP compensa-
tion allows the transient response to be optimized over
a wide range of output capacitance and ESR values. The
LTC3835-1 features a precision 0.8V reference and a power
good output indicator. The 4V to 36V input supply range
encompasses a wide range of battery chemistries.
The TRACK/SS pin ramps the output voltage during start-
up. Current foldback limits MOSFET heat dissipation during
short-circuit conditions.
Comparison of LTC3835 and LTC3835-1
PART #
LTC3835
LTC3835-1
CLKOUT/
PHASMD
YES
NO
EXTV
CC
YES
NO
PGOOD
YES
NO
PACKAGES
FE20/4
×
5 QFN
GN16/3
×
5 DFN
Wide Output Voltage Range: 0.8V ≤ V
OUT
≤ 10V
Low Operating I
Q
: 80μA
OPTI-LOOP
®
Compensation Minimizes C
OUT
±1% Output Voltage Accuracy
Wide V
IN
Range: 4V to 36V Operation
Phase-Lockable Fixed Frequency 140kHz to 650kHz
Dual N-Channel MOSFET Synchronous Drive
Very Low Dropout Operation: 99% Duty Cycle
Adjustable Output Voltage Soft-Start or Tracking
Output Current Foldback Limiting
Output Overvoltage Protection
Low Shutdown I
Q
: 10μA
Selectable Continuous, Pulse-Skipping or
Burst Mode
®
Operation at Light Loads
Small 16-Lead Narrow SSOP or 3mm
×
5mm
DFN Package
APPLICATIONS
n
n
n
n
Automotive Systems
Telecom Systems
Battery-Operated Digital Devices
Distributed DC Power Systems
L,
LT, LTC, LTM, Burst Mode, and OPTI-LOOP are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
Protected by U.S. Patents, including 5408150, 5481178, 5705919, 5929620, 6304066,
6498466, 6580258, 6611131.
TYPICAL APPLICATION
High Efficiency Step-Down Converter
PLLLPF
0.01μF
RUN
TRACK/SS
BOOST
I
TH
330pF
33k
100pF
SGND
20k
PLLIN/MODE
V
FB
62.5k
SENSE
–
SENSE
+
PGND
BG
INTV
CC
4.7μF
150μF
LTC3835-1
SW
V
IN
TG
0.22μF
3.3μH
0.012Ω
V
OUT
3.3V
5A
10μF
V
IN
4V TO 36V
100
90
80
70
EFFICIENCY (%)
60
50
40
30
20
10
0
0.001 0.01
0.1
0.1
1
10 100 1000 10000
LOAD CURRENT (mA)
38351 TA01b
38351 TA01
Efficiency and Power Loss
vs Load Current
V
IN
= 12V; V
OUT
= 3.3V
EFFICIENCY
100000
10000
POWER LOSS (mW)
1000
100
POWER LOSS
10
1
38351fc
1
LTC3835-1
ABSOLUTE MAXIMUM RATINGS
(Note 1)
Input Supply Voltage (V
IN
) ......................... 36V to –0.3V
Top Side Driver Voltage (BOOST) ............... 42V to –0.3V
Switch Voltage (SW) ..................................... 36V to –5V
INTV
CC
, (BOOST-SW) ............................... 8.5V to –0.3V
RUN, TRACK/SS ......................................... 7V to –0.3V
SENSE
+
, SENSE
–
Voltages ........................ 11V to –0.3V
PLLIN/MODE, PLLLPF .........................INTVCC to –0.3V
I
TH
, V
FB
Voltages ...................................... 2.7V to –0.3V
Peak Output Current <10μs (TG, BG) ..........................3A
INTV
CC
Peak Output Current ................................. 50mA
Operating Temperature Range (Note 2).... –40°C to 85°C
Junction Temperature (Note 3) ............................. 125°C
Storage Temperature Range
GN Package ....................................... –65°C to 150°C
Storage Temperature Range
DHC Package .................................... –65°C to 125°C
Lead Temperature (GN Package, Soldering, 10 sec).... 300°C
PIN CONFIGURATION
TOP VIEW
TOP VIEW
PLLLPF
I
TH
TRACK/SS
V
FB
SGND
PGND
BG
INTV
CC
1
2
3
4
5
6
7
8
17
16 PLLIN/MODE
15 SENSE
+
14 SENSE
–
13 RUN
12 BOOST
11 TG
10 SW
9
V
IN
PLLLPF
I
TH
TRACK/SS
V
FB
SGND
PGND
BG
INTV
CC
DHC PACKAGE
16-Pin (5mm 3mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 43.5°C/W
EXPOSED PAD (PIN 17) IS SGND
MUST BE SOLDERED TO PCB
1
2
3
4
5
6
7
8
16 PLLIN/MODE
15 SENSE
+
14 SENSE
–
13 RUN
12 BOOST
11 TG
10 SW
9
V
IN
GN PACKAGE
16-LEAD PLASTIC SSOP
T
JMAX
= 150°C,
θ
JA
= 90°C/W
ORDER INFORMATION
LEAD FREE FINISH
LTC3835EDHC-1#PBF
LTC3835IDHC-1#PBF
LTC3835EGN-1#PBF
LTC3835IGN-1#PBF
LEAD BASED FINISH
LTC3835EDHC-1
LTC3835IDHC-1
LTC3835EGN-1
LTC3835IGN-1
TAPE AND REEL
LTC3835EDHC-1#TRPBF
LTC3835IDHC-1#TRPBF
LTC3835EGN-1#TRPBF
LTC3835IGN-1#TRPBF
TAPE AND REEL
LTC3835EDHC-1#TR
LTC3835IDHC-1#TR
LTC3835EGN-1#TR
LTC3835IGN-1#TR
(Note 2)
PART MARKING*
38351
38351
38351
38351
PART MARKING*
38351
38351
38351
38351
PACKAGE DESCRIPTION
16-Lead (5mm
×
3mm) Plastic DFN
16-Lead (5mm
×
3mm) Plastic DFN
16-Lead Plastic SSOP
16-Lead Plastic SSOP
PACKAGE DESCRIPTION
16-Lead (5mm
×
3mm) Plastic DFN
16-Lead (5mm
×
3mm) Plastic DFN
16-Lead Plastic SSOP
16-Lead Plastic SSOP
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 85°C
–40°C to 85°C
–40°C to 85°C
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 85°C
–40°C to 85°C
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/
38351fc
2
LTC3835-1
ELECTRICAL CHARACTERISTICS
SYMBOL
PARAMETER
Main Control Loop
Regulated Feedback Voltage
V
FB
Feedback Current
I
VFB
Reference Voltage Line Regulation
V
REFLNREG
Output Voltage Load Regulation
V
LOADREG
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 12V, V
RUN
= 5V unless otherwise noted.
CONDITIONS
l
MIN
0.792
TYP
0.800
–5
0.002
0.1
–0.1
1.55
80
10
3.5
10
–660
99.4
1.0
0.7
100
100
50
50
40
40
70
70
180
MAX
0.808
–50
0.02
0.5
–0.5
UNITS
V
nA
%/V
%
%
mmho
μA
μA
V
%
μA
%
μA
V
mV
mV
ns
ns
ns
ns
ns
ns
ns
(Note 4); I
TH
Voltage = 1.2V
(Note 4)
V
IN
= 4V to 30V (Note 4)
(Note 4)
Measured in Servo Loop;
ΔI
TH
Voltage = 1.2V to 0.7V
Measured in Servo Loop;
ΔI
TH
Voltage = 1.2V to 2V
Transconductance Amplifier g
m
I
TH
= 1.2V; Sink/Source 5μA (Note 4)
g
m
Input DC Supply Current
(Note 5)
I
Q
Sleep Mode
RUN = 5V, V
FB
= 0.83V (No Load)
Shutdown
V
RUN
= 0V
UVLO
Undervoltage Lockout
V
IN
Ramping Down
Feedback Overvoltage Lockout
Measured at V
FB
Relative to Regulated V
FB
V
OVL
Sense Pins Total Source Current
V
SENSE–
= V
SENSE+
= 0V
I
SENSE
Maximum Duty Factor
In Dropout
DF
MAX
Soft-Start Charge Current
V
TRACK
= 0V
I
TRACK/SS
RUN Pin ON Threshold
V
RUN1
, V
RUN2
Rising
V
RUN
ON
V
FB
= 0.7V, V
SENSE–
= 3.3V
V
SENSE(MAX)
Maximum Current Sense Threshold
V
FB
= 0.7V, V
SENSE–
= 3.3V
TG Transition Time:
(Note 6)
Rise Time
C
LOAD
= 3300pF
TG1, 2 t
r
Fall Time
C
LOAD
= 3300pF
TG1, 2 t
f
BG Transition Time:
(Note 6)
Rise Time
C
LOAD
= 3300pF
BG1, 2 t
r
Fall Time
C
LOAD
= 3300pF
BG1, 2 t
f
Top Gate Off to Bottom Gate On Delay C
LOAD
= 3300pF
TG/BG t
1D
Synchronous Switch-On Delay Time
Bottom Gate Off to Top Gate On Delay C
LOAD
= 3300pF
BG/TG t
2D
Top Switch-On Delay Time
Minimum On-Time
(Note 7)
t
ON(MIN)
INTV
CC
Linear Regulator
Internal V
CC
Voltage
8.5V < V
IN
< 30V
V
INTVCCVIN
INTV
CC
Load Regulation
I
CC
= 0mA to 20mA
V
LDOVIN
Oscillator and Phase-Locked Loop
Nominal Frequency
V
PLLLPF
= No Connect
f
NOM
Lowest Frequency
V
PLLLPF
= 0V
f
LOW
Highest Frequency
V
PLLLPF
= INTV
CC
f
HIGH
Minimum Synchronizable Frequency PLLIN/MODE = External Clock; V
PLLLPF
= 0V
f
SYNCMIN
Maximum Synchronizable Frequency PLLIN/MODE = External Clock; V
PLLLPF
= 2V
f
SYNCMAX
Phase Detector Output Current
I
PLLLPF
Sinking Capability
f
PLLIN/MODE
< f
OSC
Sourcing Capability
f
PLLIN/MODE
> f
OSC
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
l
l
l
8
98
0.75
0.5
90
80
125
20
4
12
l
1.35
0.9
110
115
90
90
90
80
5.0
5.25
0.2
400
250
530
115
800
–5
5
5.5
1.0
440
280
580
140
V
%
kHz
kHz
kHz
kHz
kHz
μA
μA
360
220
475
650
Note 2:
The LTC3835E-1 is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls. The LTC3835I-1 is guaranteed to
meet performance specificatons over the full –40°C to 85°C operating
temperature range.
38351fc
3
LTC3835-1
ELECTRICAL CHARACTERISTICS
Note 3:
T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
according to the following formulas:
LTC3835GN-1: T
J
= T
A
+ (P
D
• 90°C/W)
LTC3835EDHC-1: T
J
= T
A
+ (P
D
• 43.5°C/W)
Note 4:
The LTC3835-1 is tested in a feedback loop that servos V
ITH
to a
specified voltage and measures the resultant V
FB
.
Note 5:
Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency. See Applications Information.
Note 6:
Rise and fall times are measured using 10% and 90% levels. Delay
times are measured using 50% levels.
Note 7:
The minimum on-time condition is specified for an inductor
peak-to-peak ripple current ≥40% of I
MAX
(see Minimum On-Time
Considerations in the Applications Information section).
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