LT8610AC/LT8610AC-1
42V, 3.5A Synchronous
Step-Down Regulator with
2.5µA Quiescent Current
FeaTures
n
DescripTion
The
LT
®
8610AC/LT8610AC-1
is a compact, high efficiency,
high speed synchronous monolithic step-down switching
regulator that consumes only 2.5µA of quiescent current.
Compared to the LT8610AB, the LT8610AC/LT8610AC-1
has a lower feedback voltage of 800mV and a lower mini-
mum V
IN
of 3V. The LT8610AC/LT8610AC-1 has the same
additional features of the LT8610AB as compared to the
LT8610: higher maximum output current of 3.5A, faster
minimum on time of 30ns, and higher light load efficiency.
The LT8610AC/LT8610AC-1 has a SYNC pin for syn-
chronization to an external clock. A capacitor on the TR/
SS pin programs the output voltage ramp rate during
startup. The PG flag signals when V
OUT
is within ±8% of
the programmed output voltage as well as fault conditions.
The LT8610AC-1 has internal compensation optimized for
high switching frequencies resulting in improved transient
response compared to the LT8610AC. The LT8610AC-1
also has a feature which will soft-start the part when
exiting dropout or brownout conditions reducing output
voltage overshoot.
FEEDBACK
VOLTAGE
LT8610AC
LT8610AB*
LT8610A*
LT8610*
0.80V
0.97V
0.97V
0.97V
OUTPUT MIN ON
MIN V
IN
CURRENT TIME
3.0V
3.5A
30ns
3.4V
3.4V
3.4V
3.5A
3.5A
2.5A
30ns
30ns
50ns
IMPROVED
EMI
Yes
Yes
Yes
–
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n
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LT8610 Feature Set, Plus:
3V Minimum Input Voltage
800mV Feedback Voltage
3.5A Maximum Output Current
Fast 30ns Minimum Switch-On Time
Improved Burst Mode Efficiency
Improved EMI
Wide Input Voltage Range: 3V to 42V
Ultralow Quiescent Current Burst Mode
®
Operation:
2.5μA I
Q
Regulating 12V
IN
to 3.3V
OUT
High Efficiency Synchronous Operation:
95% Efficiency at 1A, 5V
OUT
from 12V
IN
93% Efficiency at 1A, 3.3V
OUT
from 12V
IN
Low Dropout Under All Conditions: 200mV at 1A
Safely Tolerates Inductor Saturation in Overload
Adjustable and Synchronizable Frequency:
LT8610AC: 200kHz to 2.2MHz
LT8610AC-1: 1.5MHz to 2.2MHz
Accurate 1.015V Enable Pin Threshold
Output Soft-Start and Tracking
Small Thermally Enhanced 16-Lead MSOP Package
applicaTions
n
n
Automotive and Industrial Supplies
GSM Power Supplies
*See LT8610A/LT8610AB or LT8610 data sheet.
L,
LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective owners.
Typical applicaTion
5V 3.5A Step-Down Converter
V
IN
5.5V TO 42V
4.7µF
V
IN
EN/UV
LT8610AC
PG
SYNC
TR/SS
INTV
CC
RT
60.4k
f
SW
= 700kHz
BST
SW
BIAS
FB
1M
10pF
GND
191k
0.1µF
4.7µH
V
OUT
5V
47µF 3.5A
×2
100
90
80
EFFICIENCY (%)
70
60
50
40
30
0.1
Efficiency at 5V
OUT
10nF
1µF
V
IN
= 12V
V
IN
= 24V
V
IN
= 36V
1
10
100
1000
8610ac1 TA01b
LOAD CURRENT (mA)
8610ac1 TA01a
8610acfa
For more information
www.linear.com/LT8610AC
1
LT8610AC/LT8610AC-1
absoluTe MaxiMuM raTings
(Note 1)
pin conFiguraTion
TOP VIEW
SYNC
TR/SS
RT
EN/UV
V
IN
V
IN
NC
GND
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
FB
PG
BIAS
INTV
CC
BST
SW
SW
SW
V
IN
, EN/UV, PG..........................................................42V
BIAS ..........................................................................30V
BST Pin Above SW Pin................................................4V
FB, TR/SS, RT, INTV
CC
...............................................4V
SYNC Voltage .............................................................6V
Operating Junction Temperature Range (Note 2)
LT8610ACE/LT8610ACE-1 ...................... –40 to 125°C
LT8610ACI/LT8610ACI-1 ........................ –40 to 125°C
LT8610ACH/LT8610ACH-1 ..................... –40 to 150°C
Storage Temperature Range ......................–65 to 150°C
17
GND
MSE PACKAGE
16-LEAD PLASTIC MSOP
θ
JA
= 40°C/W,
θ
JC(PAD)
= 10°C/W
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
orDer inForMaTion
LEAD FREE FINISH
LT8610ACEMSE#PBF
LT8610ACIMSE#PBF
LT8610ACHMSE#PBF
LT8610ACEMSE-1#PBF
LT8610ACIMSE-1#PBF
LT8610ACHMSE-1#PBF
TAPE AND REEL
LT8610ACEMSE#TRPBF
LT8610ACIMSE#TRPBF
LT8610ACHMSE#TRPBF
LT8610ACEMSE-1#TRPBF
LT8610ACIMSE-1#TRPBF
LT8610ACHMSE-1#TRPBF
PART MARKING*
8610AC
8610AC
8610AC
610AC1
610AC1
610AC1
PACKAGE DESCRIPTION
16-Lead Plastic MSOP
16-Lead Plastic MSOP
16-Lead Plastic MSOP
16-Lead Plastic MSOP
16-Lead Plastic MSOP
16-Lead Plastic MSOP
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
–40°C to 150°C
–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.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/
elecTrical characTerisTics
PARAMETER
Minimum Input Voltage
V
IN
Quiescent Current
V
EN/UV
= 0V
CONDITIONS
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C.
MIN
l
l
TYP
2.6
1.0
1.0
1.7
1.7
0.28
30
225
MAX
3.0
3
8
4
10
0.5
60
500
0.806
0.812
0.02
20
UNITS
V
µA
µA
µA
µA
mA
µA
µA
V
V
%/V
nA
V
EN/UV
= 2V, Not Switching, V
SYNC
= 0V
l
V
EN/UV
= 2V, Not Switching, V
SYNC
= 2V
V
IN
Current in Regulation
Feedback Reference Voltage
Feedback Voltage Line Regulation
Feedback Pin Input Current
V
OUT
= 0.8V, V
IN
= 6V, Output Load = 100µA
V
OUT
= 0.8V, V
IN
= 6V, Output Load = 1mA
V
IN
= 6V, I
LOAD
= 0.5A
V
IN
= 6V, I
LOAD
= 0.5A
V
IN
= 4.0V to 42V, I
LOAD
= 1A
V
FB
= 1V
l
l
l
l
0.794
0.788
–20
0.800
0.800
0.004
8610acfa
2
For more information
www.linear.com/LT8610AC
LT8610AC/LT8610AC-1
elecTrical characTerisTics
PARAMETER
INTV
CC
Voltage
INTV
CC
Undervoltage Lockout
BIAS Pin Current Consumption
Minimum On-Time
Minimum Off-Time
Oscillator Frequency
R
T
= 221k, I
LOAD
= 1A (LT8610AC Only)
R
T
= 60.4k, I
LOAD
= 1A (LT8610AC Only)
R
T
= 18.2k, I
LOAD
= 1A (LT8610AC/LT8610AC-1)
I
SW
= 1A
l
l
l
l
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C.
CONDITIONS
I
LOAD
= 0mA, V
BIAS
= 0V
I
LOAD
= 0mA, V
BIAS
= 3.3V
V
BIAS
= 3.3V, I
LOAD
= 1A, 2MHz
I
LOAD
= 1A, SYNC = 0V
I
LOAD
= 1A, SYNC = 3.3V
l
l
MIN
3.23
3.25
2.37
15
15
180
665
1.85
5
3.4
–1.5
l
TYP
3.4
3.29
2.47
9.2
30
30
95
210
700
2.00
120
6.7
65
4.3
1.015
50
MAX
3.57
3.35
2.57
45
45
125
240
735
2.15
8
5.4
1.5
1.075
20
UNITS
V
V
V
mA
ns
ns
ns
kHz
kHz
MHz
mΩ
A
mΩ
A
µA
V
mV
nA
%
%
%
nA
Ω
V
V
µA
Ω
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 Pin Threshold
EN/UV Pin Hysteresis
EN/UV Pin Current
PG Upper Threshold Offset from V
FB
PG Lower Threshold Offset from V
FB
PG Hysteresis
PG Leakage
PG Pull-Down Resistance
SYNC Threshold
TR/SS Source Current
TR/SS Pull-Down Resistance
V
INTVCC
= 3.4V, I
SW
= 1A
V
INTVCC
= 3.4V
V
IN
= 42V, V
SW
= 0V, 42V
EN/UV Rising
V
EN/UV
= 2V
V
FB
Falling
V
FB
Rising
V
PG
= 3.3V
V
PG
= 0.1V
SYNC Falling
SYNC Rising
l
l
l
l
0.955
–20
5
–11
–40
8.0
–8.0
0.4
11
–5
40
680
0.8
1.6
1.0
1.1
2.0
2.0
230
2000
1.4
2.4
3.2
Fault Condition, TR/SS = 0.1V
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 LT8610ACE/LT8610ACE-1 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 LT8610ACI/LT8610ACI-1 is guaranteed over the full –40°C to 125°C
operating junction temperature range. The LT8610ACH/LT8610ACH-1 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 greater than 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.
8610acfa
For more information
www.linear.com/LT8610AC
3
LT8610AC/LT8610AC-1
Typical perForMance characTerisTics
100
95
90
EFFICIENCY (%)
EFFICIENCY (%)
85
80
75
70
65
60
55
50
0
0.5
1.5
2
2.5
1
LOAD CURRENT (A)
V
IN
= 12V
V
IN
= 24V
V
IN
= 36V
3
3.5
f
SW
= 700kHz (LT8610AC)
L = IHLP-2525EZ-01, 4.7µH
T
A
= 25°C, unless otherwise noted.
Efficiency at 3.3V
OUT
Efficiency at 5V
OUT
100
90
80
70
60
50
40
30
Efficiency at 5V
OUT
100
95
90
EFFICIENCY (%)
85
80
75
70
65
60
55
50
f
SW
= 700kHz (LT8610AC)
L = IHLP-2525EZ-01, 4.7µH
f
SW
= 700kHz (LT8610AC)
L = IHLP-2525EZ-01, 4.7µH
20
0.01
V
IN
= 12V
V
IN
= 24V
V
IN
= 36V
0.1
1
10
100
LOAD CURRENT (mA)
1000
8610ac1 G02
V
IN
= 12V
V
IN
= 24V
V
IN
= 36V
0
0.5
1.5
2
2.5
1
LOAD CURRENT (A)
3
3.5
8610ac1 G01
8610ac1 G03
100
90
80
EFFICIENCY (%)
70
60
50
40
30
Efficiency at 3.3V
OUT
Efficiency vs Frequency at 1A
100
V
OUT
= 3.3V
95 L = IHLP-2525EZ-01, 4.7µH
FB PIN VOLTAGE (V)
90
EFFICIENCY (%)
85
80
75
70
V
IN
= 12V
V
IN
= 24V
V
IN
= 36V
65
V
IN
= 12V
V
IN
= 24V (LT8610AC)
0.816
0.812
0.808
0.804
0.800
0.796
0.792
0.788
Reference Voltage
f
SW
= 700kHz (LT8610AC)
L = IHLP-2525EZ-01, 4.7µH
20
0.01
0.1
1
10
100
LOAD CURRENT (mA)
1000
8610ac1 G04
60
0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25
SWITCHING FREQUENCY (MHz)
8610ac1 G05
0.784
–55
–25
5
95
65
35
TEMPERATURE (°C)
125
155
8610ac1 G06
EN Pin Thresholds
1.04
1.02
1.00
0.98
EN FALLING
0.96
0.94
0.92
–55
EN RISING
CHANGE IN V
OUT
(%)
EN THRESHOLD (V)
0.25
0.20
0.15
0.10
0.05
0
–0.05
–0.10
–0.15
–0.20
–25
5
95
65
35
TEMPERATURE (°C)
125
155
–0.25
Load Regulation
V
OUT
= 3.3V
V
IN
= 12V
CHANGE IN V
OUT
(%)
0.15
0.12
0.09
0.06
0.03
0
–0.03
–0.06
–0.09
–0.12
0
0.5
1.5
2
2.5
1
LOAD CURRENT (A)
3
3.5
–0.15
Line Regulation
V
OUT
= 3.3V
I
LOAD
= 0.5A
0
5
10
15 20 25 30 35
INPUT VOLTAGE (V)
40
45
8610ac1 G07
8610ac1 G08
8610ac1 G09
8610acfa
4
For more information
www.linear.com/LT8610AC
LT8610AC/LT8610AC-1
Typical perForMance characTerisTics
No Load Supply Current
5.0
4.5
4.0
INPUT CURRENT (µA)
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
0
5
10
15 20 25 30 35
INPUT VOLTAGE (V)
40
45
0
–55
–25
65
5
95
35
TEMPERATURE (°C)
125
155
INPUT CURRENT (µA)
V
OUT
= 3.3V
IN REGULATION
25
T
A
= 25°C, unless otherwise noted.
Top FET Current Limit vs Duty Cycle
8.0
7.5
7.0
CURRENT LIMIT (A)
6.5
6.0
5.5
5.0
4.5
4.0
3.5
3.0
0
0.2
0.6
DUTY CYCLE
0.4
0.8
1.0
No Load Supply Current
V
OUT
= 3.3V
V
IN
= 12V
IN REGULATION
20
15
10
5
8610ac1 G10
8610ac1 G11
8610ac1 G12
Top FET Current Limit
7.00
6.75
6.50
CURRENT LIMIT (A)
6.25
6.00
5.75
5.50
5.25
5.00
4.75
4.50
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
30% DC
5.50
5.25
5.00
CURRENT LIMIT (A)
Bottom FET Current Limit
250
Switch Drop
SWITCH CURRENT = 1A
200
SWITCH DROP (mV)
4.75
4.50
4.25
4.00
3.75
3.50
3.25
3.00
150
TOP SW
100
BOT SW
50
–55
–25
95
5
35
65
TEMPERATURE (°C)
125
155
0
–55
–25
65
5
95
35
TEMPERATURE (°C)
125
155
8610ac1 G13
8610ac1 G14
8610ac1 G15
Switch Drop
450
400
MINIMUM ON-TIME (ns)
350
SWITCH DROP (mV)
300
250
200
150
100
50
0
0
0.5
1
1.5
2
SWITCH CURRENT (A)
2.5
3
TOP SW
BOT SW
45
Minimum On-Time
I
LOAD
= 1.5A
43 V
SYNC
= 5V
MINIMUM OFF-TIME (ns)
41
39
37
35
33
31
29
27
25
–55
–25
V
OUT
= 3.3V
V
OUT
= 0.8V
5
65
95
35
TEMPERATURE (°C)
125
155
125
120
115
110
105
100
95
90
85
80
Minimum Off-Time
V
OUT
= 3.3V
I
LOAD
= 0.5A
75
–50 –25
5
95
65
35
TEMPERATURE (°C)
125
155
8610ac1 G16
8610ac1 G17
8610ac1 G18
8610acfa
For more information
www.linear.com/LT8610AC
5
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