42V, 2.5A Synchronous
8610 TA01a
OUT
V
5.5V TO 42V
SW
Step-Down Regulator
with 2.5µA Quiescent
FEATURES DESCRIPTION
n
Wide Input Voltage Range: 3.4V to 42V
n
Ultralow Quiescent Current Burst Mode® Operation:
2.5μA I
Output Ripple < 10mV
n
High Efficiency Synchronous Operation:
96% Efficiency at 1A, 5V
94% Efficiency at 1A, 3.3V
n
Fast Minimum Switch-On Time: 50ns
n
Low Dropout Under All Conditions: 200mV at 1A
n
Allows Use Of Small Inductors
n
Low EMI
n
Adjustable and Synchronizable: 200kHz to 2.2MHz
n
Current Mode Operation
n
Accurate 1V Enable Pin Threshold
n
Internal Compensation
n
Output Soft-Start and Tracking
n
Small Thermally Enhanced 16-Lead MSOP Package
Regulating 12VIN to 3.3V
Q
P-P
from 12VIN
OUT
from 12VIN
OUT
OUT
APPLICATIONS
n
Automotive and Industrial Supplies
n
General Purpose Step-Down
n
GSM Power Supplies
The LT®8610 is a compact, high efficiency, high speed
synchronous monolithic step-down switching regulator
that consumes only 2.5µA of quiescent current. To p and
bottom power switches are included with all necessary
circuitry to minimize the need for external components.
Low ripple Burst Mode operation enables high efficiency
down to very low output currents while keeping the output
ripple below 10mV
P-P
to an external clock. Internal compensation with peak current mode
results
topology allows the use of small inductors and
in fast transient response and good loop stability.
The EN/UV pin has an accurate 1V threshold and can be
used to program V
undervoltage lockout or to shut down
IN
the LT8610 reducing the input supply current to 1µA. A
capacitor on the TR/SS pin programs the output voltage
ramp rate during start-up. The PG flag signals when V
is within ±9% of the programmed output voltage as well
as fault conditions. The LT8610 is available in a small
16-lead MSOP package with exposed pad for low thermal
resistance.
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.
LT8610
Current
. A SYNC pin allows synchronization
OUT
TYPICAL APPLICATION
5V 2.5A Step-Down Converter 12VIN to 5V
IN
4.7µF
10nF
1µF
f
IN
EN/UV
PG
SYNC
TR/SS
INTV
RT
60.4k
= 700kHz
CC
LT8610
PGND
BSTV
SW
BIAS
FB
GND
0.1µF
4.7µH
1M
10pF
243k
For more information www.linear.com/LT8610
47µF
V
5V
2.5A
100
95
90
85
80
75
70
EFFICIENCY (%)
65
60
55
50
0
0.5
1
LOAD CURRENT (A)
Efficiency
OUT
1.5
fSW = 700kHz
VIN = 12V
= 24V
V
IN
2
8610 G01
2.5
8610fa
1
LT8610
EN/UV
CC
TOP VIEW
16-LEAD PLASTIC MSOP
PIN CONFIGURATIONABSOLUTE MAXIMUM RATINGS
(Note 1)
VIN, EN/UV, PG ..........................................................42V
BIAS .......................................................................... 30V
BST Pin Above SW Pin................................................4V
FB, TR/SS, RT, INTV
. ..............................................4V
CC
SYNC Voltage . ............................................................ 6V
Operating Junction Temperature Range (Note 2)
LT8610E ................................................. –40 to 125°C
LT8610I .................................................. –40 to 125°C
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
SYNC
TR/SS
V
V
PGND
PGND
RT
IN
IN
θ
JA
1
2
3
4
5
6
7
8
MSE PACKAGE
= 40°C/W, θ
17
GND
JC(PAD)
16
15
14
13
12
11
10
9
= 10°C/W
FB
PG
BIAS
INTV
BST
SW
SW
SW
LT8610H ................................................–40 to 150°C
Storage Temperature Range ......................–65 to 150°C
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LT8610EMSE#PBF LT8610EMSE#TRPBF 8610 16-Lead Plastic MSOP –40°C to 125°C
LT8610IMSE#PBF LT8610IMSE#TRPBF 8610 16-Lead Plastic MSOP –40°C to 125°C
LT8610HMSE#PBF LT8610HMSE#TRPBF 8610 16-Lead Plastic MSOP –40°C to 150°C
Consult LT C Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LT C 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
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C.
PARAMETER CONDITIONS MIN TYP MAX UNITS
Minimum Input Voltage
Quiescent Current V
V
IN
Current in Regulation V
V
IN
Feedback Reference V
Feedback V
oltage Line Regulation V
oltage V
Feedback Pin Input Current V
Voltage I
INTV
CC
Undervoltage Lockout 2.5 2.6 2.7 V
INTV
CC
BIAS Pin Current Consumption V
Minimum On-Time I
Minimum Off-T
ime 50 80 110 ns
= 0V, V
EN/UV
= 2V, Not Switching, V
V
EN/UV
= 2V, Not Switching, V
V
EN/UV
= 0.97V, VIN = 6V, Output Load = 100µA
OUT
V
= 0.97V, VIN = 6V, Output Load = 1mA
OUT
= 6V, I
IN
V
= 6V, I
IN
= 4.0V to 42V, I
IN
= 1V –20 20 nA
FB
= 0mA, V
LOAD
I
= 0mA, V
LOAD
= 3.3V, I
BIAS
= 1A, SYNC = 0V
LOAD
I
= 1A, SYNC = 3.3V
LOAD
= 0V
SYNC
= 0V
SYNC
= 2V 0.24 0.5 mA
SYNC
= 0.5A
LOAD
= 0.5A
LOAD
= 0.5A
LOAD
= 0V
BIAS
= 3.3V
BIAS
= 1A, 2MHz 8.5 mA
LOAD
l
l
l
l
l
l
l
l
l
0.964
0.958
3.23
3.25
30
30
2.9 3.4 V
1.0
1.0
1.7
1.7
24
210
0.970
0.970
3
8
4
10
50
350
0.976
0.982
µA
µA
µA
µA
µA
µA
0.004 0.02 %/V
3.4
3.29
50
45
3.57
3.35
70
65
ns
ns
8610fa
V
V
V
V
2
For more information www.linear.com/LT8610
LT8610
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C.
PARAMETER CONDITIONS MIN TYP MAX UNITS
Oscillator Frequency R
Top Power NMOS On-Resistance
= 221k, I
T
R
= 60.4k, I
T
R
= 18.2k, I
T
= 1A 120 mΩ
I
SW
LOAD
LOAD
LOAD
= 1A
= 1A
= 1A
Top Power NMOS Current Limit
Bottom Power NMOS On-Resistance V
Bottom Power NMOS Current Limit V
SW Leakage Current V
= 3.4V, I
INTVCC
= 3.4V 2.5 3.3 4.8 A
INTVCC
= 42V, VSW = 0V, 42V –1.5 1.5 µA
IN
= 1A 65 mΩ
SW
EN/UV Pin Threshold EN/UV Rising
EN/UV Pin Hysteresis 40 mV
EN/UV Pin Current V
PG Upper Threshold Offset from V
PG Lower Threshold Offset from V
FB
FB
= 2V –20 20 nA
EN/UV
VFB Falling
VFB Rising
PG Hysteresis 1.3 %
PG Leakage V
PG Pull-Down Resistance V
= 3.3V –40 40 nA
PG
= 0.1V
PG
SYNC Threshold SYNC Falling
SYNC Rising
SYNC Pin Current V
= 2V –40 40 nA
SYNC
TR/SS Source Current
TR/SS Pull-Down Resistance Fault Condition, TR/SS = 0.1V 230 Ω
l
180
l
665
l
1.85
l
3.5 4.8 5.8 A
l
0.94 1.0 1.06 V
l
l
l
6 9.0 12 %
–6 –9.0 –12 %
0.8
1.6
l
1.2 2.2 3.2 µA
210
700
2.00
240
735
2.15
680 2000 Ω
1.1
2.0
1.4
2.4
kHz
kHz
MHz
V
V
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 LT8610E 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
LT8610I is guaranteed over the full –40°C to 125°C operating junction
temperature range. The LT8610H 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.
For more information www.linear.com/LT8610
8610fa
3
LT8610
8610 G03
8610 G04
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency at 5V
100
95
90
85
80
75
70
EFFICIENCY (%)
65
60
55
50
0.5
0
Efficiency at 3.3V
100
90
80
70
60
50
40
EFFICIENCY (%)
30
20
10
0
0.001 10 100 1000 10000
0.01 0.1 1
OUT
1.5
1
LOAD CURRENT (A)
OUT
LOAD CURRENT (mA)
fSW = 700kHz
fSW = 700kHz
VIN = 12V
V
IN
VIN = 12V
= 24V
V
IN
2
8610 G01
= 24V
2.5
Efficiency at 3.3V
100
95
90
85
80
75
70
EFFICIENCY (%)
65
60
55
50
0.5
0
OUT
1.5
1
LOAD CURRENT (A)
fSW = 700kHz
VIN = 12V
= 24V
V
IN
2
8610 G02
2.5
Efficiency at 5V
100
90
80
70
60
50
40
EFFICIENCY (%)
30
20
10
0
0.01
0.001 0.1 1 10 100 1000
Efficiency vs Frequency Reference Voltage
96
V
OUT
94
92
90
88
EFFICIENCY (%)
86
84
82
0.25
= 3.3V
VIN = 12V
= 24V
V
IN
0.75 1.25 2.25
SWITCHING FREQUENCY (MHz)
1.75
8610 G05
0.985
0.982
0.979
0.976
0.973
0.970
0.967
0.964
REFERENCE VOLTAGE (V)
0.961
0.958
0.955
–55
–25
OUT
LOAD CURRENT (mA)
65
35
5
TEMPERATURE (°C)
fSW = 700kHz
VIN = 12V
= 24V
V
IN
95 125
10000
155
8610 G06
EN Pin Thresholds Load Regulation Line Regulation
1.04
1.03
1.02
1.01
1.00
0.99
0.98
EN THRESHOLD (V)
0.97
0.96
0.95
–55
4
5
–25
TEMPERATURE (°C)
EN RISING
EN FALLING
35 155
65
95 125
8610 G07
0.25
V
= 3.3V
OUT
0.20
0.15
0.10
(%)
0.05
OUT
–0.05
–0.10
CHANGE IN V
–0.15
–0.20
–0.25
= 12V
V
IN
0
0.5
0
1.5 2
1
LOAD CURRENT (A)
2.5
For more information www.linear.com/LT8610
3
8610 G08
0.10
0.08
0.06
0.04
(%)
0.02
OUT
0
–0.02
–0.04
CHANGE IN V
–0.06
–0.08
–0.10
V
= 3.3V
OUT
= 0.5A
I
LOAD
105
0
INPUT VOLTAGE (V)
2015
30 35 45
25
40
8610 G09
8610fa
TYPICAL PERFORMANCE CHARACTERISTICS
8610 G13
8610 G14
LT8610
No Load Supply Current No Load Supply Current
5.0
V
= 3.3V
OUT
4.5
IN REGULATION
4.0
3.5
3.0
2.5
2.0
1.5
INPUT CURRENT (µA)
1.0
0.5
0
5 15
10
0
25 45
20
INPUT VOLTAGE (V)
30
35
40
8610 G10
25
V
= 3.3V
OUT
= 12V
V
IN
IN REGULATION
20
15
10
INPUT CURRENT (µA)
5
0
–55 –25
5
35
TEMPERATURE (°C)
Top FET Current Limit Bottom FET Current Limit
5.0
4.5
4.0
3.5
CURRENT LIMIT (A)
3.0
30% DC
70% DC
3.6
3.4
3.2
3.0
2.8
CURRENT LIMIT (A)
2.6
Top FET Current Limit vs Duty Cycle
6.0
5.5
5.0
4.5
4.0
3.5
CURRENT LIMIT (A)
3.0
2.5
65
95
125
155
8610 G11
2.0
0.2 0.4 0.8
0
DUTY CYCLE
0.6
1.0
Switch Drop
250
SWITCH CURRENT = 1A
200
150
100
SWITCH DROP (mV)
50
TOP SW
BOT SW
2.5
–55
–25
450
400
350
300
250
200
150
SWITCH DROP (mV)
100
50
0
0
0.5
5 35 65
TEMPERATURE (°C)
TOP SW
BOT SW
1
1.5 3
SWITCH CURRENT (A)
2
95 125
2.5
8610 G41
2.4
–55
–25
TEMPERATURE (°C)
Minimum On-TimeSwitch Drop
80
75
70
65
60
55
50
45
MINIMUM ON-TIME (ns)
40
35
30
–55
I
LOAD
I
LOAD
I
LOAD
I
LOAD
5
–25
TEMPERATURE (°C)
= 1A, V
= 1A, V
= 2.5A, V
= 2.5A, V
5 35 65
= 0V
SYNC
= 3V
SYNC
= 0V
SYNC
= 3V
SYNC
65
35
95 125
95 125
8610 G15
8610 G17
155
0
–55 –25
5
TEMPERATURE (°C)
Minimum Off-Time
100
VIN = 3.3V
= 0.5A
I
LOAD
95
90
85
80
75
MINIMUM OFF-TIME (ns)
70
65
60
–25 5 65
–50
TEMPERATURE (°C)
65
35
35
95
95 125 155
125
155
8610 G40
8610 G18
8610fa
For more information www.linear.com/LT8610
5
LT8610
8610 G20
8610 G23
8610 G24
8610 G25
8610 G26
TYPICAL PERFORMANCE CHARACTERISTICS
Dropout Voltage Switching Frequency
800
700
600
500
400
300
200
DROPOUT VOLTAGE (mV)
100
0
0
1 2
0.5
LOAD CURRENT (A)
1.5 2.5
3
8610 G19
740
RT = 60.4k
730
720
710
700
690
680
SWITCHING FREQUENCY (kHz)
670
660
–25 5 65
–55
35
TEMPERATURE (°C)
95 125 155
Burst Frequency
800
VIN = 12V
= 3.3V
V
OUT
700
600
500
400
300
200
SWITCHING FREQUENCY (kHz)
100
0
0
Minimum Load to Full Frequency
(SYNC DC High) Soft-Start Tracking
100
V
= 5V
OUT
= 700kHz
f
SW
80
60
40
LOAD CURRENT (mA)
20
0
5 10
20
15 25 40 45
INPUT VOLTAGE (V)
30 35
8610 G39
Frequency Foldback
800
V
= 3.3V
OUT
= 12V
V
IN
700
600
500
400
300
200
SWITCHING FREQUENCY (kHz)
100
= 0V
V
SYNC
= 60.4k
R
T
0
0.2 0.4 0.8
0
FB VOLTAGE (V)
0.6
8610 G22
1
1.2
1.0
0.8
0.6
FB VOLTAGE (V)
0.4
0.2
0
0
0.2 0.4
50
100
LOAD CURRENT (mA)
0.8 1.2 1.4
0.6 1.0
TR/SS VOLTAGE (V)
150
200
8610 G21
Soft-Start Current
2.4
VSS = 0.5V
2.3
2.2
2.1
2.0
1.9
SS PIN CURRENT (µA)
1.8
1.7
1.6
–25 5 65
–50
6
35
TEMPERATURE (°C)
95 125 155
PG High Thresholds PG Low Thresholds
12.0
11.5
(%)
11.0
REF
10.5
10.0
9.5
9.0
8.5
8.0
7.5
PG THRESHOLD OFFSET FROM V
7.0
–55
–25
FB RISING
FB FALLING
65
35
5
TEMPERATURE (°C)
95 125
For more information www.linear.com/LT8610
155
–7.0
–7.5
(%)
–8.0
REF
–8.5
–9.0
–9.5
–10.0
–10.5
–11.0
–11.5
PG THRESHOLD OFFSET FROM V
–12.0
–55
–25
FB RISING
FB FALLING
65
35
5
TEMPERATURE (°C)
95 125
155
8610fa
TYPICAL PERFORMANCE CHARACTERISTICS
RT Programmed Switching
Frequency
250
225
200
175
150
125
100
75
RT PIN RESISTOR (kΩ)
50
25
0
0.6
0.2
SWITCHING FREQUENCY (MHz)
1.4
1.8
1
2.2
8610 G27
VIN UVLO Bias Pin Current
3.6
3.4
3.2
3.0
2.8
2.6
INPUT VOLTAGE (V)
2.4
2.2
2.0
–25 5 65
–55
35
TEMPERATURE (°C)
95 125 155
8610 G28
5.00
V
= 5V
BIAS
= 5V
V
OUT
4.75
4.50
4.25
4.00
3.75
BIAS PIN CURRENT (mA)
3.50
3.25
3.00
5
I
LOAD
= 700kHz
f
SW
10
= 1A
15
INPUT VOLTAGE (V)
LT8610
25
30
20
35
40
45
8610 G29
Bias Pin Current
12
V
= 5V
BIAS
= 5V
V
OUT
10
= 12V
V
IN
= 1A
I
LOAD
8
6
4
BIAS PIN CURRENT (mA)
2
0
0
0.5 1 1.5 2
SWITCHING FREQUENCY (MHz)
Switching Waveforms
I
L
1A/DIV
V
SW
10V/DIV
36V
TO 5V
IN
OUT
500ns/DIV
AT 1A
8610 G30
8610 G33
2.5
1A/DIV
V
SW
5V/DIV
I
LOAD
1A/DIV
V
OUT
100mV/DIV
Switching Waveforms Switching Waveforms
I
L
8610 G31
12V
IN
TO 5V
OUT
500ns/DIV
AT 1A
200mA/DIV
V
SW
5V/DIV
I
L
12V
V
SYNC
IN
TO 5V
= 0V
OUT
500µs/DIV
AT 10mA
Transient Response Transient Response
I
LOAD
1A/DIV
V
OUT
200mV/DIV
0.5A TO 1.5A TRANSIENT
, 5V
12V
IN
C
= 47µF
OUT
50µs/DIV
OUT
8610 G34
0.5A TO 2.5A TRANSIENT
12V
, 5V
IN
C
= 47µF
OUT
50µs/DIV
OUT
8610 G32
8610 G35
For more information www.linear.com/LT8610
8610fa
7
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