shutdown protects the power components from thermal
stress. Soft recovery from output shorts or overcurrent
minimizes output overshoot.
The LTC3867 features a precision 0.6V reference and
can regulate output voltages up to 14V from a wide
4V to 38V input supply range. The LTC3867 includes
a high speed differential remote sense amplifier. Burst
Mode
®
operation, continuous and pulse-skipping modes
are supported. The LTC3867 is available in a 24-lead
(4mm
×
4mm) QFN package.
n
n
n
n
n
n
n
n
n
n
V
IN
Range: 4V to 38V
V
OUT
Range: 0.6V to 14V
Nonlinear Control Architecture Minimizes Output
Transient Excursions (Optional)
Programmable DCR Temperature Compensation
±0.75% 0.6V Voltage Reference
Fixed Frequency Range of 200kHz to 1.2MHz
PLL Frequency Synchronization
R
SENSE
or DCR Current Sensing
Differential Remote Output Voltage Sense
Supports Smooth Start-Up into Pre-Biased Outputs
Programmable Soft-Start or V
OUT
Tracking
Hiccup Mode/Soft Recovery from Output Overcurrent
24-Lead (4mm
×
4mm) QFN Package
APPLICATIONS
n
n
n
n
Automotive Systems
Telecom Systems
Industrial Equipment
Distributed DC Power Systems
L,
LT, LTC, LTM, Burst Mode, OPTI-LOOP Linear Technology and the Linear logo are registered
,
trademarks of Linear Technology Corporation. All other trademarks are the property of their
respective owners. Protected by U.S. Patents, including 5481178, 5705919, 5929620, 6177787,
6580258, 6498466, 6611131.
TYPICAL APPLICATION
High Efficiency Synchronous Step-Down Controller
DIFF
+
ITEMP
DIFF
–
ITSD
DIFFOUT PGOOD
I
LIM
RUN
TK/SS
EXTV
CC
V
IN
FREQ
MODE/PLLIN TG
IFAST
LTC3867
BOOST
I
TH
SW
D
B
SGND
49.9k
V
FB
75k
SENSE
–
SENSE
+
BG
PGND
INTV
CC
3.3k
0.22µF
SGND
INTV
CC
V
IN
5V TO 18V
EFFICIENCY (%)
100
90
22µF
50V
0.1µF
0.4µH
V
OUT
1.5V
10A
330µF
×2
+100µF
80
70
60
50
40
30
20
10
0
0.01
0.1
1
10
LOAD CURRENT (A)
Efficiency and Power Loss
4.0
3.5
3.0
POWER LOSS (W)
2.5
2.0
1.5
1.0
0.5
0
100
3867 TA01b
0.1µF
37.4k
INTV
CC
330pF
49.9k
100pF
+
4.7µF
3867 TA01a
3867f
1
LTC3867
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
MODE/PLLIN
PGOOD
SENSE
+
SENSE
–
UF PACKAGE
24-LEAD (4mm
×
4mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 47°C/W,
θ
JC
= 4.5°C/W
EXPOSED PAD (PIN 25) IS SGND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC3867EUF#PBF
LTC3867IUF#PBF
TAPE AND REEL
LTC3867EUF#TRPBF
LTC3867IUF#TRPBF
PART MARKING*
3867
3867
PACKAGE DESCRIPTION
24-Lead (4mm
×
4mm) Plastic QFN
24-Lead (4mm
×
4mm) Plastic QFN
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based finish parts.
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/
TK/SS
IFAST
ITSD
I
LIM
V
IN
Voltage ..................................................–0.3V to 40V
BST Voltage.................................................–0.3V to 46V
SW Voltage.....................................................–5V to 40V
(BST-SW) Voltage .........................................–0.3V to 6V
RUN, PGOOD, EXTV
CC
, INTV
CC
Voltage .........–0.3V to 6V
SENSE
+
, SENSE
–
......................................... –0.3V to 15V
INTV
CC
Peak Output Current .................................100mA
DIFF
–
......................................................–0.3V to INTV
CC
All Other Pin Voltages Except TG, BG ......–0.3V to INTV
CC
Operating Junction Temperature Range ...–40°C to 125°C
Storage Temperature Range .................. –65°C to 150°C
FREQ
BST
24 23 22 21 20 19
RUN 1
DIFF
+
SW
18 PGND
17 BG
16 INTV
CC
15 V
IN
14 EXTV
CC
13 ITEMP
2
3
25
SGND
DIFF
–
DIFFOUT 4
V
FB
5
I
TH
6
7
8
9 10 11 12
TG
3867f
2
LTC3867
ELECTRICAL CHARACTERISTICS
SYMBOL
V
IN
V
OUT
V
FB
I
FB
V
REFLNREG
V
LOADREG
g
m
V
OVL
I
Q
DF
MAX
UVLO
UVLO
HYS
I
SENSE
I
TEMP
I
FAST
I
TK/SS
V
RUN
V
RUN(HYS)
I
RUN
V
SENSE(MAX)
PARAMETER
Input Voltage Range
Output Voltage Range
Regulated Feedback Voltage
Feedback Current
Reference Voltage Line Regulation
Output Voltage Load Regulation
Transconductance Amplifier g
m
Feedback Overvoltage Lockout
Input DC Supply Current
Normal Mode
Shutdown
Maximum Duty Factor
Undervoltage Lockout
UVLO Hysteresis
Sense Pin Bias Currents
DCR Tempco Compensation Current
Fast Transient Programming Current
Soft-Start Charge Current
RUN Pin On Threshold
RUN Pin On Hysteresis
RUN Pin Pull-Up Current
RUN < On Threshold
RUN > On Threshold
Maximum Current Sense Threshold
RUN < 1.1V
RUN > 1.34V
I
TH
=1.85V, V
SENSE
=3.3V
I
LIM
= 0V
I
LIM
= 1.5V
I
LIM
= Float
I
LIM
= 3.7V
I
LIM
= INTV
CC
(Note 6)
l
l
l
l
l
The
l
denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at T
A
= 25°C (Note 2). V
IN
= 15V, V
RUN
= 5V unless otherwise specified.
CONDITIONS
MIN
4
0.6
I
TH
=1.2V, 0°C to 85°C
I
TH
=1.2V, –40°C to 125°C (Note 3)
V
IN
= 4.5V to 38V
ΔI
TH
=1.2V to 0.7V
ΔI
TH
=1.2V to 1.6V
I
TH
=1.2V, Sink/Source 5µA
Measured at V
FB
V
RUN
= 0V (Note 4)
In Dropout, f
SW
= 600kHz
V
INTVCC
Falling
V
SENSE
= 3.3V
V
ITEMP
= 500mV
V
IFAST
= 500mV
V
TK/SS
= 0V
V
RUN
Rising
l
l
l
l
l
l
l
l
TYP
MAX
38
14
UNITS
V
V
mV
mV
nA
%/V
%
%
mmho
%
mA
µA
%
V
mV
µA
µA
µA
µA
V
mV
µA
µA
Main Control Loop/Whole System
595.5
594
600
600
–15
0.002
0.01
–0.01
2
604.5
606
–50
0.02
0.1
–0.1
10
5
7.5
3.5
30
50
3.4
±2
33
11
1.4
1.34
96
3.0
98
3.2
600
±1
27
9
1
1.1
30
10
1.25
1.22
80
1
5
25
35
45
55
69
30
40
50
60
75
65
90
35
45
55
65
79
mV
mV
mV
mV
mV
ns
t
ON(MIN)
Power Good
V
PGOOD(ON)
I
PGOOD(OFF)
t
PGOOD
V
PG1
Minimum On-Time
PGOOD Pull-Down Resistance
PGOOD Leakage Current
PGOOD Delay
PGOOD Trip Level—with Delay
200
2
Ω
µA
µs
V
PGOOD
= 5V
V
PGOOD
High to Low
V
FB
with Respect to Set Output Voltage
V
FB
Ramping Up
V
FB
Ramping Down
–2
45
5
–5
7.5
–7.5
10
–10
%
%
3867f
3
LTC3867
ELECTRICAL CHARACTERISTICS
SYMBOL
V
PG1(HYST)
V
PG2
V
PG2(HYST)
V
INTVCC
V
LDO
INT
V
EXTVCC
V
LDO
EXT
V
LDO(HYS)
V
DA
I
DIFF
+
f
0dB
I
OUT(SINK)
I
OUT(SOURCE)
f
OSC
PARAMETER
PGOOD Trip Level Hysteresis
PGOOD 2nd Trip Level—No Delay
V
FB
with Respect to Set Output Voltage
V
FB
Ramping Up
V
FB
Ramping Down
The
l
denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at T
A
= 25°C (Note 2). V
IN
= 15V, V
RUN
= 5V unless otherwise specified.
CONDITIONS
MIN
TYP
2
17
–25
5
6V < V
IN
< 38V
I
CC
= 0mA to 20mA
EXTV
CC
Ramping Positive
I
CC
= 20mA, V
EXTVCC
= 5V
4.5
5.1
5.3
0.5
4.7
50
200
Measured in a Servo Loop with EA in Loop
I
TH
=1.2V, 0°C to 85°C
I
TH
=1.2V, –40°C to 125°C
DIFF
+
to SGND
(Note 7)
DIFFOUT = 600mV
DIFFOUT = 600mV
R
FREQ
< 23.2kΩ
R
FREQ
= 30.1kΩ
R
FREQ
= 47.5kΩ
R
FREQ
= 54.9kΩ
R
FREQ
= 75.0kΩ
Maximum Frequency
Minimum Frequency
V
FREQ
= 0.8V
70
5.5
2
MAX
UNITS
%
%
%
%
V
%
V
mV
mV
PGOOD 2nd Trip Level Hysteresis
Linear Regulator Voltage
INTV
CC
Load Regulation
EXTV
CC
Switchover Voltage
EXTV
CC
Voltage Drop
EXTV
CC
Hysteresis
DIFF
+
Accuracy
INTV
CC
Linear Regulator
Differential Amplifier
595.5
594
–200
4
100
500
150
250
600
750
1.05
0.2
20
250
TG High
TG Low
BG High
BG Low
2.6
1.5
2.4
1.1
21
600
600
604.5
606
200
mV
mV
nA
MHz
µA
µA
kHz
kHz
kHz
kHz
MHz
MHz
MHz
µA
kΩ
Ω
Ω
Ω
Ω
l
Input Bias Current
DA Unity-Gain Crossover Frequency
Maximum Sinking Current
Maximum Sourcing Current
Oscillator Frequency
Oscillator and Phase-Locked Loop
1.2
19
I
FREQ
R
MODE/PLLIN
On-Chip Driver
TG R
UP
TG R
DOWN
BG R
UP
BG R
DOWN
FREQ Pin Output Current
MODE/PLLIN Input Resistance
TG Pull-Up R
DS(ON)
TG Pull-Down R
DS(ON)
BG Pull-Up R
DS(ON)
BG Pull-Down R
DS(ON)
3867f
4
LTC3867
ELECTRICAL CHARACTERISTICS
SYMBOL
TG t
r
TG t
f
BG t
r
BG t
f
TG/BG t
1D
BG/TG t
2D
PARAMETER
TG Transition Time
Rise Time
Fall Time
BG Transition Time
Rise Time
Fall Time
Top Gate Off to Bottom Gate On Delay,
Synchronous Switch-On Delay Time
Bottom Gate Off to Top Gate On Delay,
Top Switch-On Delay Time
Source Current
Comparator Trip Point
The
l
denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at T
A
= 25°C (Note 2). V
IN
= 15V, V
RUN
= 5V unless otherwise specified.
CONDITIONS
C
LOAD
= 3300pF
C
LOAD
= 3300pF (Note 5)
C
LOAD
= 3300pF
C
LOAD
= 3300pF (Note 5)
C
LOAD
= 3300pF Each Driver
C
LOAD
= 3300pF Each Driver
MIN
TYP
25
25
25
25
30
30
MAX
UNITS
ns
ns
ns
ns
ns
ns
Thermal Shutdown
I
ITSD
V
ITSD
I
ITSD
= 500mV
20
950
µA
mV
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.
Note 2:
The LTC3867 is tested under pulsed load conditions such that
T
J
≈ T
A
. The LTC3867E is guaranteed to meet performance specifications
from 0°C to 85°C operating junction temperature. Specifications over
the –40°C to 125°C operating junction temperature range are assured by
design, characterization and correlation with statistical process controls.
The LTC3867I is guaranteed to meet performance specifications over the
full –40°C to 125°C operating junction temperature range. The maximum
ambient temperature consistent with these specifications is determined
by specific operating conditions in conjunction with board layout, the
package thermal impedance and other environmental factors.
T
J
is calculated from the ambient temperature, T
A
, and power dissipation,
P
D
, according to the following formula:
LTC3867UF: T
J
= T
A
+ (P
D
• 47°C/W)
Note 3:
The LTC3867 is tested in a feedback loop that servos V
ITH
to a
specified voltage and measures the resultant V
FB
.
Note 4:
Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency. See Applications Information.
Note 5:
Rise and fall times are measured using 10% and 90% levels. Delay
times are measured using 50% levels.
Note 6:
The minimum on-time condition corresponds to the on inductor
peak-to-peak ripple current ≥40% of I
MAX
(see Minimum On-Time
Considerations in the Applications Information section).
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