step-down DC/DC converter that can deliver up to 12A
output current from a 4V to 24V (28V maximum) input
supply. It uses a valley current control architecture to de-
liver very low duty cycle operation at high frequency with
excellent transient response. The operating frequency is
selected by an external resistor and is compensated for
variations in V
IN
and V
OUT
.
The LTC3610 can be configured for discontinuous or
forced continuous operation at light load. Forced continu-
ous operation reduces noise and RF interference while
discontinuous mode provides high efficiency by reducing
switching losses at light loads.
Fault protection is provided by internal foldback current
limiting, an output overvoltage comparator and an optional
short-circuit shutdown timer. Soft-start capability for sup-
ply sequencing is accomplished using an external timing
capacitor. The regulator current limit is user programmable.
A power good output voltage monitor indicates when
the output is in regulation. The LTC3610 is available in a
compact 9mm
×
9mm QFN package.
12A Output Current
Wide V
IN
Range = 4V to 24V
Internal N-Channel MOSFETs
True Current Mode Control
Optimized for High Step-Down Ratios
t
ON(MIN)
≤100ns
Extremely Fast Transient Response
Stable with Ceramic C
OUT
±1% 0.6V Voltage Reference
Power Good Output Voltage Monitor
Adjustable On-Time/Switching Frequency
Adjustable Current Limit
Programmable Soft-Start
Output Overvoltage Protection
Optional Short-Circuit Shutdown Timer
Low Shutdown I
Q
: 15µA
Available in a 9mm
×
9mm 64-Pin QFN Package
applications
■
■
Point of Load Regulation
Distributed Power Systems
L,
LT, LTC, LTM, 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, 6100678, 6580258, 5847554, 6304066.
typical application
High Efficiency Step-Down Converter
0.1µF
V
ON
RUN/SS
100pF
LTC3610
0.47µH
470pF
31.83k
I
TH
SGND
SW
0.22µF
BOOST
INTV
CC
FCB
V
RNG
PGOOD
EXTV
CC
4.7µF
PGND
V
FB
3610 TA01a
I
ON
V
IN
604k
V
IN
4V TO 24V
V
OUT
2.5V
12A
100
95
90
EFFICIENCY (%)
85
80
75
70
65
60
55
50
0.01
9.5k
Efficiency vs Load Current
10000
V
IN
= 5V
V
IN
= 12V
1000
POWER LOSS (mW)
10µF
×3
100µF
×2
100
POWER LOSS 12V
POWER LOSS 5V
V
OUT
= 2.5V
0.1
1
LOAD CURRENT (A)
10
3610
TA01b
30.1k
10
1
3610ff
LTC3610
absolute MaxiMuM ratings
(Note 1)
pin conFiguration
TOP VIEW
54 INTV
CC
53 INTV
CC
50 SGND
64 PGND
63 PGND
62 PGND
61 PGND
60 PGND
59 PGND
58 PGND
57 PGND
56 PGND
55 SW
49 SGND
52 SV
IN
51 SV
IN
Input Supply Voltage (V
IN
, I
ON
) .................. 28V to –0.3V
Boosted Topside Driver Supply Voltage
(BOOST) ................................................ 34V to –0.3V
SW Voltage ............................................ 28V to –0.3V
INTV
CC
, EXTV
CC
, (BOOST – SW), RUN/SS,
PGOOD Voltages ...................................... 7V to –0.3V
FCB, V
ON
, V
RNG
Voltages............ INTV
CC
+ 0.3V to –0.3V
I
TH
, V
FB
Voltages ....................................... 2.7V to –0.3V
Operating Temperature Range
(Note 4) ............................................. –40°C to 125°C
Junction Temperature (Note 2) ............................. 125°C
Storage Temperature Range................... –55°C to 125°C
PGND 1
PGND 2
PGND 3
SW 4
SW 5
SW 6
SW 7
SW 8
SW 9
SW 10
SW 11
PV
IN
12
PV
IN
13
PV
IN
14
PV
IN
15
PV
IN
16
65
PGND
48 SGND
47 SGND
46 SGND
45 SGND
44 EXTV
CC
43 V
FB
66
SW
42 SGND
41 I
ON
40 SGND
68
SGND
39 FCB
38 I
TH
37 V
RNG
36 PGOOD
35 V
ON
34 SGND
33 SGND
67
PV
IN
SGND 28
RUN/SS 30
SGND 31
WP PACKAGE
64-LEAD (9mm × 9mm) QFN MULTIPAD
T
JMAX
= 125°C,
θ
JA
= 28°C/W
LEAD FREE FINISH
LTC3610EWP#PBF
LTC3610IWP#PBF
orDer inForMation
TAPE AND REEL
LTC3610EWP#TRPBF
TAPE AND REEL
LTC3610EWP#TR
LTC3610IWP#TR
LTC3610IWP#TRPBF
PART MARKING*
LTC3610WP
LTC3610WP
PART MARKING*
LTC3610WP
LTC3610WP
PACKAGE DESCRIPTION
64-Lead (9mm
×
9mm) Plastic QFN
64-Lead (9mm
×
9mm) Plastic QFN
PACKAGE DESCRIPTION
64-Lead (9mm
×
9mm) Plastic QFN
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
TEMPERATURE RANGE
–40°C to 125°C
LEAD BASED FINISH
LTC3610EWP
LTC3610IWP
–40°C to 125°C
64-Lead (9mm
×
9mm) Plastic QFN
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/
electrical characteristics
SYMBOL
Main Control Loop
V
IN
I
Q
V
FB
ΔV
FB(LINEREG)
Operating Input Voltage Range
Input DC Supply Current
Normal
Shutdown Supply Current
Feedback Reference Voltage
Feedback Voltage Line Regulation
PARAMETER
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C (Note 4). V
IN
= 15V unless otherwise noted.
CONDITIONS
MIN
4
900
15
I
TH
= 1.2V (Note 3)
V
IN
= 4V to 28V, I
TH
= 1.2V (Note 3)
●
TYP
BOOST 29
MAX
24
2000
30
0.606
SGND 32
PV
IN
17
PV
IN
18
PV
IN
19
PV
IN
20
PV
IN
21
PV
IN
22
PV
IN
23
PV
IN
24
PV
IN
25
SW 26
NC 27
UNITS
V
µA
µA
V
%/V
3610ff
0.594
0.600
0.002
LTC3610
electrical characteristics
SYMBOL
ΔV
FB(LOADREG)
I
FB
g
m(EA)
V
FCB
I
FCB
t
ON
t
ON(MIN)
t
OFF(MIN)
I
VALLEY(MAX)
I
VALLEY(MIN)
ΔV
FB(OV)
V
RUN/SS(ON)
V
RUN/SS(LE)
V
RUN/SS(LT)
I
RUN/SS(C)
I
RUN/SS(D)
V
IN(UVLO)
V
IN(UVLOR)
R
DS(ON)
PARAMETER
Feedback Voltage Load Regulation
Feedback Input Current
Error Amplifier Transconductance
Forced Continuous Threshold
Forced Continuous Pin Current
On-Time
Minimum On-Time
Minimum Off-Time
Maximum Valley Current
Maximum Reverse Valley Current
Output Overvoltage Fault Threshold
RUN Pin Start Threshold
RUN Pin Latchoff Enable Threshold
RUN Pin Latchoff Threshold
Soft-Start Charge Current
Soft-Start Discharge Current
Undervoltage Lockout
Undervoltage Lockout Release
Top Switch On-Resistance
Bottom Switch On-Resistance
Internal V
CC
Voltage
Internal V
CC
Load Regulation
EXTV
CC
Switchover Voltage
EXTV
CC
Switch Drop Voltage
EXTV
CC
Switchover Hysteresis
PGOOD Upper Threshold
PGOOD Lower Threshold
PGOOD Hysteresis
PGOOD Low Voltage
V
FB
Rising
V
FB
Falling
V
FB
Returning
I
PGOOD
= 5mA
7
–7
6V < V
IN
< 28V, V
EXTVCC
= 4V
I
CC
= 0mA to 20mA, V
EXTVCC
= 4V
I
CC
= 20mA, V
EXTVCC
Rising
I
CC
= 20mA, V
EXTVCC
= 5V
●
●
●
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C (Note 4). V
IN
= 15V unless otherwise noted.
CONDITIONS
I
TH
= 0.5V to 1.9V (Note 3)
V
FB
= 0.6V
I
TH
= 1.2V (Note 3)
V
FCB
= 0.6V
I
ON
= 60µA, V
ON
= 1.5V
I
ON
= 60µA, V
ON
= 0V
I
ON
= 180µA, V
ON
= 0V
I
ON
= 30µA, V
ON
= 1.5V
V
RNG
= 0.5V, V
FB
= 0.56V, FCB = 0V
V
RNG
= 0V, V
FB
= 0.56V, FCB = 0V
V
RNG
= 0.5V, V
FB
= 0.64V, FCB = 0V
V
RNG
= 0V, V
FB
= 0.64V, FCB = 0V
7
0.8
RUN/SS Pin Rising
RUN/SS Pin Falling
V
RUN/SS
= 0V
V
RUN/SS
= 4.5V, V
FB
= 0V
V
IN
Falling
V
IN
Rising
●
●
●
●
●
●
MIN
TYP
–0.05
–5
MAX
–0.3
±50
2
0.66
–2
310
100
500
UNITS
%
nA
mS
V
µA
ns
ns
ns
ns
A
A
A
A
1.4
0.54
170
1.7
0.6
–1
250
120
60
290
7
10
16
19
–6
–9
10
1.5
4
3.5
13
2
4.5
4.2
–3
3
3.9
4
16
10
5.5
±2
300
%
V
V
V
µA
µA
V
V
mΩ
mΩ
V
%
V
mV
mV
–0.5
0.8
–1.2
1.8
3.4
3.5
12
6.5
Internal V
CC
Regulator
V
INTVCC
ΔV
LDO(LOADREG)
V
EXTVCC
ΔV
EXTVCC
ΔV
EXTVCC(HYS)
PGOOD Output
ΔV
FBH
ΔV
FBL
ΔV
FB(HYS)
V
PGL
10
–10
1
0.15
13
–13
2.5
0.4
%
%
%
V
4.7
4.5
5
–0.1
4.7
150
500
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:
T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
as follows:
T
J
= T
A
+ (P
D
• 28°C/W) (θ
JA
is simulated per JESD51-7 high effective
thermal conductivity test board)
θ
JC
= 0.24°C/W (θ
JC
is simulated when heat sink is applied at the
bottom of the package).
Note 3:
The LTC3610 is tested in a feedback loop that adjusts V
FB
to
achieve a specified error amplifier output voltage (I
TH
).
Note 4:
The LTC3610 is tested under pulsed load conditions such that
T
J
≈ T
A
. The LTC3610E is guaranteed to meet performance specifications
from 0°C to 125°C. Specifications over the –40°C to 125°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls. The LTC3610I is guaranteed over the
full –40°C to 125°C operating junction temperature range. Note that
the maximum ambient temperature is determined by specific operating
conditions in conjunction with board layout, the rated package thermal
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