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LT8697_15

USB 5V 2.5A Output, 42V Input Synchronous Buck with Cable Drop Compensation

厂商名称:Linear ( ADI )

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LT8697
USB 5V 2.5A Output,
42V Input Synchronous Buck with
Cable Drop Compensation
FEATURES
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DESCRIPTION
The
LT
®
8697
is a compact, high efficiency, high speed
synchronous monolithic step-down switching regulator
designed to power 5V USB applications. A precise output
voltage and programmable cable drop compensation main-
tain accurate 5V regulation at the USB socket connected
to the end of a long cable. Forced continuous operation
allows the LT8697 to sink current, further enhancing ac-
curate 5V regulation during load transients.
Accurate and programmable output current limit, a power
good indicator pin and an output current monitor pin
improve system reliability and safety, allow the user to
implement latch-off or auto-retry functionality and can
eliminate the need for a USB switch IC. Dual feedback al-
lows regulation on the output of a USB switch and limits
cable drop compensation to a maximum of 5.8V output,
protecting USB devices during fault conditions. Thermal
shutdown provides additional protection by limiting power
dissipation in the IC during an overtemperature fault.
The LT8697 is available in a small 24-lead 3mm × 5mm
package with an exposed pad for low thermal resistance.
L,
LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective owners.
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Wide Input Range: 5V to 42V
Low Dropout Under All Conditions: 450mV at 2.1A
Accurate 5V Output: ±1.3% Over Full Temperature
Range
Programmable Cable Drop Compensation
Programmable Output Current Limit
Output Current Monitor
Dual Input Feedback Permits Regulation on Output
of USB Switch
Forced Continuous Mode for Fast Load Step
Response
High Efficiency Synchronous Operation at 2MHz:
93% Efficiency at 2.1A, 5V
OUT
from 12V
IN
95% Efficiency at 0.9A, 5V
OUT
from 12V
IN
Fast Minimum Switch-On Time: 45ns
Adjustable Output from 5.0V to 5.25V
Adjustable and Synchronizable: 300kHz to 2.2MHz
Small Thermally Enhanced 3mm × 5mm 24-Lead
QFN Package
Automotive and Industrial USB
Precision 5V Supply
APPLICATIONS
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TYPICAL APPLICATION
2MHz 5V Step-Down Converter with Cable Drop Compensation
V
IN
6V TO 42V
4.7µF
V
IN
EN/UV
PG
INTV
CC
1µF
ICTRL
SYNC
TR/SS
10nF
16.5k
RT
GND
LT8697
BST
3.3µH
SW
SYS
ISP
ISN
USB5V
RCBL
PGND
18.2k
0.1Ω
47µF
×2
0.018Ω
0.1µF
V
OUT
3 METERS AWG 20
TWISTED PAIR CABLE
0.1Ω
VOLTAGE (V)
5.25
V
OUT
V
LOAD
4
CURRENT (A)
Transient Response Through 3 Meters
AWG 20 Twisted-Pair Cable
5.50
5
1nF
10k
5.00
3
+
LOAD
V
LOAD
5V, 2.4A
4.75
4.50
I
LOAD
50mA/µs
2
1
4.25
8697 TA01a
100µs/DIV
0
8697 TA01b
8697fb
For more information
www.linear.com/LT8697
1
LT8697
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
ICTRL
RCBL
ISN
ISP
20 USB5V
19 PG
18 SYS
25
GND
17 INTV
CC
16 BST
15 SW
14 SW
13 SW
9 10 11 12
NC
NC
NC
NC
V
IN
, EN/UV, PG, ISP, ISN ...........................................42V
SYS ...........................................................................30V
USB5V .....................................................................3mA
BST Above SW ............................................................4V
TR/SS, ICTRL..............................................................4V
RT, RCBL.....................................................................2V
SYNC ..........................................................................6V
Operating Junction Temperature Range (Notes 2, 3)
LT8697E ............................................ –40°C to 125°C
LT8697I ............................................. –40°C to 125°C
LT8697H ............................................ –40°C to 150°C
Storage Temperature Range .................. –65°C to 150°C
24 23 22 21
SYNC 1
TR/SS 2
RT 3
EN/UV 4
V
IN
5
V
IN
6
PGND 7
PGND 8
UDD PACKAGE
24-LEAD (3mm
×
5mm) PLASTIC QFN
θ
JA
= 46°C/W,
θ
JC
= 5°C/W
EXPOSED PAD (PIN 25) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LT8697EUDD#PBF
LT8697IUDD#PBF
LT8697HUDD#PBF
TAPE AND REEL
LT8697EUDD#TRPBF
LT8697IUDD#TRPBF
LT8697HUDD#TRPBF
PART MARKING*
LGGW
LGGW
LGGW
PACKAGE DESCRIPTION
24-Lead (3mm
×
5mm) Plastic QFN
24-Lead (3mm
×
5mm) Plastic QFN
24-Lead (3mm
×
5mm) Plastic QFN
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
–40°C to 150°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/
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Notes 2, 4)
PARAMETER
V
IN
Undervoltage Lockout
V
IN
Shutdown Current
V
IN
Current in Regulation
V
IN
to Disable Forced Continuous Mode
Output Sink Current in Forced Continuous Mode
USB5V Voltage
USB5V Voltage Line Regulation
Regulated Load Voltage Through 0.3Ω
USB5V Clamp Voltage
V
EN/UV
= 0.3V
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ELECTRICAL CHARACTERISTICS
CONDITIONS
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MIN
TYP
2.9
1
MAX
3.4
3
8
12
31
1.7
5.02
5.04
25
5.075
UNIT
V
µA
µA
mA
V
A
V
V
mV
V
V
V
IN
= 12V, I
LOAD
= 100µA, R
T
= 56.2k
V
IN
Rising
V
USB5V
= 5.5V, L = 6.8µH, R
T
= 56.2k
V
IN
= 12V
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9
27
0.6
4.96
4.91
4.925
29
1
4.99
4.99
6
5
9
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V
IN
= 6V to 42V
V
IN
= 12V, I
LOAD
= 2.1A, Voltage at Point of Load (End
of Cable), R
CBL
= 13.7k, R
CDC
= 10k, R
SENSE
= 20mΩ
I
USB5V
= 3mA
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8697fb
2
For more information
www.linear.com/LT8697
LT8697
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Notes 2, 4)
PARAMETER
USB5V Current
 
Current Sense Voltage (V
ISP
– V
ISN
)
CONDITIONS
V
ISN
= 5V, V
ISP
– V
ISN
= 40mV, R
CBL
= 13.7k
V
ISN
= 5V, V
ISP
– V
ISN
= 10mV, R
CBL
= 13.7k
V
ISN
= 5V, V
ISP
– V
ISN
= 0V, R
CBL
= 13.7k
R
CBL
= Open
V
CTRL
= 1.5V, V
ISN
= 5V
V
CTRL
= 1.5V, V
ISN
= 0V
V
CTRL
= 800mV, V
ISN
= 5V
V
CTRL
= 800mV, V
ISN
= 0V
V
CTRL
= 200mV, V
ISN
= 5V
V
CTRL
= 200mV, V
ISN
= 0V
V
ISP
– V
ISN
= 40mV, R
CBL
= 13.7k
V
ISP
– V
ISN
= 10mV, R
CBL
= 13.7k
V
ISP
– V
ISN
= 50mV, V
RCBL
= 0V
V
ISP
= V
ISN
= 0V, 5V
V
ICTRL
= 1.5V
V
SYS
= 0V, 5V
2.6
V
IN
= 12V
V
SYS
= 5V, R
T
= 56.2k
V
SYS
= 5V, I
LOAD
= 2.1A
96
I
LOAD
= 1A
I
LOAD
= 0.5A
6.2
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ELECTRICAL CHARACTERISTICS
MIN
57.5
12
0
0
45
43
34.5
34
4.5
3.5
720
115
–2
–20
–0.5
TYP
60
15
2
1
48
48.5
39.5
40
9.5
10
800
205
–3
–2
3.4
2.9
5.8
7.5
4
450
97.5
45
80
7
300
700
2.00
120
4.8
4.8
65
4.5
0.1
1.0
40
MAX
62.5
23
8
2
51
54
44.5
46
14.5
16.5
880
305
–4
20
–3
3.15
5.92
5
99
70
110
7.9
340
750
2.05
6
6
5.8
5
1.06
20
UNIT
µA
µA
µA
µA
mV
mV
mV
mV
mV
mV
mV
mV
mA
µA
µA
V
V
V
V
mA
mV
%
ns
ns
V
kHz
kHz
MHz
A
A
A
µA
V
mV
nA
%
%
%
Ω
µs
V
V
µA
µA
Ω
8697fb
RCBL Monitor Voltage
RCBL Output Current Limit
ISP, ISN Bias Current
ICTRL Current
INTV
CC
Voltage
INTV
CC
Undervoltage Lockout
SYS Voltage in SYS Regulation
SYS Voltage to Disable Forced Continuous Mode
SYS Current in Regulation
Dropout Voltage (V
IN
– V
SYS
)
Maximum Duty Cycle in Dropout
Minimum On-Time
Minimum Off-Time
Oscillator Frequency
5.63
3
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30
Minimum V
IN
for SYS Regulation at Full Frequency R
T
= 16.5k, V
USB5V
= 0V, I
LOAD
= 0.5A
R
T
= 140k
R
T
= 56.2k
R
T
= 16.5k
I
SW
= 1A
E-, I-Grades
H-Grade
V
INTVCC
= 3.4V, I
SW
= 1A
V
INTVCC
= 3.4V
V
IN
= 42V, V
SW
= 0V, 42V
V
EN/UV
Rising
V
EN/UV
= 2V
V
USB5V
Falling
V
USB5V
Rising
V
PG
= 0.1V
V
USB5V
from 5V to 4V
V
SYNC
Falling
V
SYNC
Rising
V
SYNC
= 2V
V
TR/SS
= 0V
Fault Condition, V
TR/SS
= 0.1V
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250
620
1.85
3.2
2.9
3.5
0.94
–20 
6
–6
Top Power NMOS On-Resistance
Top Power NMOS Current Limit
Bottom Power NMOS On-Resistance
Bottom Power NMOS Current Limit
SW Leakage Current
EN/UV Threshold
EN/UV Hysteresis
EN/UV Bias Current
PG Upper Threshold Offset from V
USB5V
PG Lower Threshold Offset from V
USB5V
PG Hysteresis
PG Pull-Down Resistance
PG Transition Delay
SYNC Threshold
SYNC Pin Current
TR/SS Current
TR/SS Pull-Down Resistance
9
–9
1.3
680
40
12
–12
2000
1.4
2.4
1
–3.2
l
0.8
1.6
–1
–1.2
1.1
2.0
–2.2
230
For more information
www.linear.com/LT8697
3
LT8697
ELECTRICAL CHARACTERISTICS
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 LT8697E is guaranteed to meet performance specifications
from 0°C to 125°C 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
LT8697I is guaranteed over the full –40°C to 125°C operating junction
temperature range. The LT8697H is guaranteed over the full –40°C to
150°C operating junction temperature range. High junction temperatures
degrade operating lifetimes. Operating lifetime is derated at junction
temperatures above 125°C.
Note 3:
This IC includes overtemperature protection that is intended to
protect the device during overload conditions. Junction temperature will
exceed 150°C when overtemperature protection is active. Continuous
operation above the specified maximum operating junction temperature
will reduce lifetime.
Note 4:
Polarity specification for current into a pin is positive and out of
a pin is negative. All voltages are referenced to GND unless otherwise
specified. MAX and MIN refer to absolute values.
TYPICAL PERFORMANCE CHARACTERISTICS
5.00
T
A
= 25°C, unless otherwise noted.
I
USB5V
vs Temperature
R
CBL
= 13.7k
V
SENSE
= 40mV
V
USB5V
vs Temperature
5.02
V
USB5V
vs V
IN
70
60
50
I
USB5V
(µA)
4.98
5.01
V
USB5V
(V)
V
USB5V
(V)
4.96
5.00
40
30
20
V
SENSE
= 10mV
4.94
4.99
4.92
4.98
10
6
10
14
18
22 26
V
IN
(V)
30
34
38
42
0
–55
V
SENSE
= 0mV
–25
5
65
35
95
TEMPERATURE (°C)
125
155
4.90
–55
–25
5
65
35
95
TEMPERATURE (°C)
125
155
4.97
8697 G01
8697 G02
8697 G03
250
225
200
175
I
USB5V
(µA)
I
USB5V
vs V
SENSE
64
62
I
USB5V
vs Frequency
V
IN
= 12V
R
CDC
= 10k
R
CBL
= 13.3k
I
LOAD
= 2A
R
SENSE
= 20m
V
SENSE
(mV)
60
50
40
30
20
10
0
V
SENSE
vs V
CTRL
R
CBL
= 4.12k
125
100
75
50
25
0
0
10
30
20
V
SENSE
(mV)
R
CBL
= 13.7k
R
CBL
= 40.2k
40
50
8697 G04
I
USB5V
(µA)
150
60
58
56
54
0.2
0.7
1.2
FREQUENCY (MHz)
1.7
2.2
8697 G05
0
0.2
0.4
0.8
0.6
V
CTRL
(V)
1
1.2
8697 G06
8697fb
4
For more information
www.linear.com/LT8697
LT8697
TYPICAL PERFORMANCE CHARACTERISTICS
1.03
1.02
EN/UV THRESHOLD (V)
1.01
EFFICIENCY (%)
1.00
0.99
0.98
0.97
0.96
0.95
–55
–25
35
95
5
65
TEMPERATURE (°C)
125
155
EN/UV FALLING
EN/UV RISING
T
A
= 25°C, unless otherwise noted.
Efficiency vs I
LOAD
V
EN
vs Temperature
100
95
90
Efficiency vs I
LOAD
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
85
80
75
70
65
60
55
50
0
0.5
1.5
1
LOAD CURRENT (A)
f
SW
= 2MHz
R
SENSE
= 18m
DCR
L
= 20m
R
CBL
= OPEN
V
IN
= 8V
V
IN
= 12V
V
IN
= 24V
2
2.5
8697 G08
f
SW
= 2MHz
R
SENSE
= 18m
DCR
L
= 20m
R
CBL
= OPEN
V
IN
= 8V
V
IN
= 12V
V
IN
= 24V
00.01
1
0.1
LOAD CURRENT (A)
10
8697 G09
0
0.001
8697 G07
Efficiency vs Frequency
100
16
14
INPUT CURRENT (mA)
90
EFFICIENCY (%)
12
10
8
6
4
2
2.2
8697 G10
No Load Supply Current vs V
IN
f
SW
= 700kHz
No Load Supply Current
vs Temperature
10.0
NO LOAD INPUT CURRENT (mA)
9.5
9.0
8.5
8.0
7.5
7.0
–55
f
SW
= 700kHz
V
IN
= 12V
80
70
L = 15µH
R
SENSE
= 18m
DCR
L
= 40m
R
CBL
= OPEN
I
LOAD
= 0.9A
V
IN
= 8V
V
IN
= 12V
V
IN
= 24V
0.7
1.7
1.2
FREQUENCY (MHz)
60
0.2
0
6
12
24
30
18
INPUT VOLTAGE (V)
36
42
8697 G11
–25
5
35
65
95
TEMPERATURE (°C)
125
155
8697 G12
Top FET Current Limit
vs Duty Cycle
5.0
5.0
Top FET Current Limit
vs Temperature
5.0
30% DC
Bottom FET Current Limit
vs Temperature
4.5
CURRENT LIMIT (A)
CURRENT LIMIT (A)
4.6
70% DC
CURRENT LIMIT (A)
4.6
4.0
4.2
4.2
3.5
3.8
3.8
3.0
2.5
T
A
= 155°C
T
A
= 125°C
T
A
= 25°C
0
0.2
0.4
0.6
DUTY CYCLE (%)
0.8
1.0
8697 G13
3.4
3.4
3.0
–55
–25
5
35
65
95
TEMPERATURE (°C)
125
155
3.0
–55
–25
5
35
65
95
TEMPERATURE (°C)
125
155
8697 G14
8697 G15
8697fb
For more information
www.linear.com/LT8697
5
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