High Efficiency 1.5V/15A, 1.2V/15A Step-Down Converter
2.2Ω
1μF
100
4.7μF
V
IN
0.1μF
0.47μH
TG1
BOOST1
SW1
BG1
INTV
CC
TG2
BOOST2
SW2
BG2
PGND
FREQ
SENSE2
+
0.1μF
EFFICIENCY (%)
0.47μH
90
80
70
60
50
40
30
20
1000pF
SENSE1
–
SENSE2
–
VID21
VID11
VID12
VID22
V
OSENSE2
V
OSENSE1
I
TH2
I
TH1
TK/SS1
SGND TK/SS2
100pF
0.1μF
0.1μF
162k
100Ω
V
OUT2
1.2V
15A
C
OUT5,6
100pF
100μF
2mΩ
10
0
0.01
0.1
1
10
LOAD CURRENT (A)
0.01
100
3865 TA01b
+
22μF
50V
V
IN
4.5V TO 24V
Efficiency and Power Loss
vs Load Current
V
IN
= 12V
V
OUT
= 1.5V
10
POWER LOSS (W)
EFFICIENCY
POWER LOSS
1
LTC3865
0.1
100Ω
2mΩ
1000pF
100Ω
V
OUT1
1.5V
15A
SENSE1
+
100Ω
+
C
OUT2,3
100μF
1000pF
10k
+
1000pF
15k
3865 TA01a
3865fb
1
LTC3865/LTC3865-1
ABSOLUTE MAXIMUM RATINGS
(Note 1)
Input Supply Voltage (V
IN
) ......................... –0.3V to 40V
Topside Driver Voltages
BOOST1, BOOST2.................................. –0.3V to 46V
Switch Voltage (SW1, SW2) ......................... –5V to 40V
INTV
CC
, RUN1, RUN2, PGOOD(s), EXTV
CC
,
(BOOST1-SW1), (BOOST2-SW2) ................. –0.3V to 6V
SENSE1
+
, SENSE2
+
, SENSE1
–
, SENSE2
–
V
OSENSE1
, V
OSENSE2
Voltages .................... –0.3V to 5.8V
MODE/PLLIN, I
LIM
, TK/SS1, TK/SS2, VID11,
VID12, VID21, VID22, FREQ Voltages ... –0.3V to INTV
CC
I
TH1
, I
TH2
Voltages .................................... –0.3V to 2.7V
INTV
CC
DC Output Current (Note 9) .......................80mA
Operating Junction Temperature Range (Notes 2, 3)
LTC3865/LTC3865-1 .......................... –40°C to 125°C
Storage Temperature Range................... –65°C to 125°C
Lead Temperature (Soldering, 10 sec)
FE Package ....................................................... 300°C
PIN CONFIGURATION
LTC3865
LTC3865
TOP VIEW
RUN1
TOP VIEW
MODE/PLLIN
SENSE1
–
SENSE1
+
SENSE1
+
SENSE
–
NC
SW1
TG1
V
OSENSE1
TK/SS1
24 BOOST1
23 BG1
22 V
IN
33
SGND
21 INTV
CC
20 EXTV
CC
19 BG2
18 PGND
17 BOOST2
9 10 11 12 13 14 15 16
RUN2
VID21
PGOOD
SW2
SENSE2
–
SENSE2
+
I
LIM
TG2
I
TH1
SGND
VID11
1
2
3
4
5
6
7
8
9
39
SGND
38 FREQ
37 VID22
36 MODE/PLLIN
35 SW1
34 TG1
33 BOOST1
32 PGND1
31 BG1
30 V
IN
29 INTV
CC
28 EXTV
CC
27 BG2
26 PGND2
25 BOOST2
24 NC
23 TG2
22 SW2
21 PGOOD1
20 PGOOD2
32 31 30 29 28 27 26 25
V
OSENSE1
1
TK/SS1 2
I
TH1
3
VID11 4
VID12 5
I
TH2
6
TK/SS2 7
V
OSENSE2
8
VID22
RUN1
FREQ
VID12 10
I
TH2
11
TK/SS2 12
V
OSENSE2
13
NC 14
SENSE2
–
15
SENSE2
+
16
RUN2 17
VID21 18
I
LIM
19
UH PACKAGE
32-LEAD (5mm 5mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 34°C/W,
θ
JC
= 3°C/W
EXPOSED PAD (PIN 33) IS SGND, MUST BE SOLDERED TO PCB
FE PACKAGE
38-LEAD PLASTIC TSSOP
T
JMAX
= 125°C,
θ
JA
= 25°C/W
EXPOSED PAD (PIN 39) IS SGND, MUST BE SOLDERED TO PCB
3865fb
2
LTC3865/LTC3865-1
PIN CONFIGURATION
LTC3865-1
TOP VIEW
MODE/PLLIN
SENSE1
–
SENSE1
+
VID22
RUN1
FREQ
SW1
SW2
32 31 30 29 28 27 26 25
V
OSENSE1
1
TK/SS1 2
I
TH1
3
VID11 4
VID12 5
I
TH2
6
TK/SS2 7
V
OSENSE2
8
9 10 11 12 13 14 15 16
RUN2
PGOOD2
PGOOD1
VID21
SENSE2
–
SENSE2
+
TG2
33
SGND
24 BOOST1
23 BG1
22 V
IN
21 INTV
CC
20 EXTV
CC
19 BG2
18 PGND
17 BOOST2
UH PACKAGE
32-LEAD (5mm 5mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 34°C/W,
θ
JC
= 3°C/W
EXPOSED PAD (PIN 33) IS SGND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC3865EUH#PBF
LTC3865EUH-1#PBF
LTC3865IUH#PBF
LTC3865IUH-1#PBF
LTC3865EFE#PBF
LTC3865IFE#PBF
TAPE AND REEL
LTC3865EUH#TRPBF
LTC3865EUH-1#TRPBF
LTC3865IUH#TRPBF
LTC3865IUH-1#TRPBF
LTC3865EFE#TRPBF
LTC3865IFE#TRPBF
PART MARKING*
3865
38651
3865
38651
LTC3865FE
LTC3865FE
PACKAGE DESCRIPTION
32-Lead (5mm
×
5mm) Plastic QFN
32-Lead (5mm
×
5mm) Plastic QFN
32-Lead (5mm
×
5mm) Plastic QFN
32-Lead (5mm
×
5mm) Plastic QFN
38-Lead Plastic TSSOP
38-Lead Plastic TSSOP
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–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/
TG1
3865fb
3
LTC3865/LTC3865-1
ELECTRICAL CHARACTERISTICS
SYMBOL
V
IN
V
OSENSE1,2
PARAMETER
Input Voltage
Output Voltage Sensing (E-Grade)
(Note 4) I
TH1,2
Voltage = 1.2V
VID11 = VID21 = GND, VID12 = VID22 = GND
VID11 = VID21 = GND, VID12 = VID22 = Float
VID11 = VID21 = GND, VID12 = VID22 = INTV
CC
VID11 = VID21 = Float, VID12 = VID22 = GND
VID11 = VID21 = Float, VID12 = VID22 = Float
VID11 = VID21 = Float, VID12 = VID22 = INTV
CC
VID11 = VID21 = INTV
CC
, VID12 = VID22 = GND
VID11 = VID21 = INTV
CC
, VID12 = VID22 = Float
VID11 = VID21 = INTV
CC
, VID12 = VID22 = INTV
CC
(Note 4) I
TH1,2
Voltage = 1.2V
VID11 = VID21 = GND, VID12 = VID22 = GND
VID11 = VID21 = GND, VID12 = VID22 = Float
VID11 = VID21 = GND, VID12 = VID22 = INTV
CC
VID11 = VID21 = Float, VID12 = VID22 = GND
VID11 = VID21 = Float, VID12 = VID22 = Float
VID11 = VID21 = Float, VID12 = VID22 = INTV
CC
VID11 = VID21 = INTV
CC
, VID12 = VID22 = GND
VID11 = VID21 = INTV
CC
, VID12 = VID22 = Float
VID11 = VID21 = INTV
CC
, VID12 = VID22 = INTV
CC
(Note 4) VID11 = VID21 = VID12 = VID22 = Float
V
IN
= 4.5V to 38V (Note 4)
(Note 4)
Measured in Servo Loop;
ΔI
TH
Voltage = 1.2V to 0.7V
Measured in Servo Loop;
ΔI
TH
Voltage = 1.2V to 1.6V
I
TH1,2
= 1.2V; Sink/Source 5μA; (Note 4)
(Note 5)
V
IN
= 15V
V
RUN1,2
= 0V
V
INTVCC
Ramping Down
Measured at V
OSENSE1,2
with VID Pins Floating
(Each Channel); V
SENSE1,2
= 3.3V
In Dropout
V
TK/SS1,2
= 0V
V
RUN1
, V
RUN2
Rising
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
The
l
denotes the specifications which apply over the full operating
junction temperature range, otherwise specifications are at T
A
= 25°C (Note 2). V
IN
= 15V, V
RUN1,2
= 5V unless otherwise noted.
CONDITIONS
MIN
4.5
1.089
0.990
1.188
1.485
0.596
1.782
2.463
3.251
4.925
1.084
0.985
1.182
1.478
0.593
1.773
2.450
3.234
4.900
1.100
1.000
1.200
1.500
0.602
1.800
2.500
3.300
5.000
1.100
1.000
1.200
1.500
0.602
1.800
2.500
3.300
5.000
–10
0.002
0.01
–0.01
2.2
3
30
3.3
0.55
0.64
94
0.9
1.1
0.66
±1
95
1.3
1.22
80
4.5
V
ITH1,2
= 3.3V, I
LIM
= 0V
V
ITH1,2
= 3.3V, I
LIM
= Float (Note 8)
V
ITH1,2
= 3.3V, I
LIM
= INTV
CC
In Overvoltage Condition
V
ITH1,2
= 3.3V, I
LIM
= 0V
V
ITH1,2
= 3.3V, I
LIM
= Float (Note 8)
V
ITH1,2
= 3.3V, I
LIM
= INTV
CC
In Overvoltage Condition
TG High
TG Low
BG High
l
l
l
l
l
l
l
l
TYP
MAX
38
1.111
1.010
1.212
1.515
0.608
1.818
2.538
3.350
5.075
1.117
1.015
1.218
1.523
0.611
1.827
2.550
3.366
5.100
–50
0.02
0.1
–0.1
UNITS
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
nA
%/V
%
%
mmho
mA
μA
V
V
Main Control Loops
Output Voltage Sensing (I-Grade)
I
OSENSE1,2
V
REFLNREG
V
LOADREG
Feedback Current
Reference Voltage Line Regulation
Output Voltage Load Regulation
g
m1,2
I
Q
Transconductance Amplifier g
m
Input DC Supply Current
Normal Mode
Shutdown
Undervoltage Lockout on INTV
CC
UVLO Hysteresis
Feedback Overvoltage Lockout
Sense Pins Total Current
Maximum Duty Cycle
Soft-Start Charge Current
RUN Pin On Threshold
RUN Pin On Hysteresis
RUN Pin Current Hysteresis
50
UVLO
UVLO
HYS
V
OVL
I
SENSE
DF
MAX
I
TK/SS1,2
V
RUN1,2
V
RUN1,2HYS
I
RUN1,2HYS
0.68
±2
1.7
1.35
V
μA
%
μA
V
mV
μA
V
SENSE(MAX)
Maximum Current Sense Threshold
(E-Grade)
24
44
68
–63
22
42
66
–65
30
50
75
–53
30
50
75
–53
2.6
1.5
3
36
56
82
–43
38
58
84
–41
mV
mV
mV
mV
mV
mV
mV
mV
Ω
Ω
Ω
3865fb
Maximum Current Sense Threshold
(I-Grade)
TG R
UP
TG R
DOWN
BG R
UP
TG Driver Pull-Up On-Resistance
TG Driver Pull-Down On-Resistance
BG Driver Pull-Up On-Resistance
4
LTC3865/LTC3865-1
ELECTRICAL CHARACTERISTICS
SYMBOL
BG R
DOWN
TG1,2 t
r
TG1,2 t
f
BG1,2 t
r
BG1,2 t
f
TG/BG t
1D
BG/TG t
2D
t
ON(MIN)
V
INTVCC
V
LDO
INT
V
EXTVCC
V
LDO
EXT
V
LDOHYS
f
NOM
f
LOW
f
HIGH
I
FREQ
V
PGL
I
PGOOD
V
PG
PARAMETER
BG Driver Pull-Down On-Resistance
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
Minimum On-Time
Internal V
CC
Voltage
INTV
CC
Load Regulation
EXTV
CC
Switchover Voltage
EXTV
CC
Voltage Drop
EXTV
CC
Hysteresis
Nominal Frequency
Lowest Frequency
Highest Frequency
Frequency Setting Current
PGOOD Voltage Low
PGOOD Leakage Current
PGOOD Trip Level
R
FREQ
= 162k
R
FREQ
= 0Ω
R
FREQ
≥ 325k
V
FREQ
= 1.22V
I
PGOOD
= 2mA
V
PGOOD
= 5V
V
OSENSE
with Respect to Set Regulated Voltage
VID11 = VID12 = VID21 = VID22 = Float
V
OSENSE
Ramping Negative
V
OSENSE
Ramping Postitive
Measured from VID Transitition Edge
450
210
650
6.5
The
l
denotes the specifications which apply over the full operating
junction temperature range, otherwise specifications are at T
A
= 25°C (Note 2). V
IN
= 15V, V
RUN1,2
= 5V unless otherwise noted.
CONDITIONS
BG Low
(Note 6)
C
LOAD
= 3300pF
C
LOAD
= 3300pF
(Note 6)
C
LOAD
= 3300pF
C
LOAD
= 3300pF
C
LOAD
= 3300pF Each Driver
C
LOAD
= 3300pF Each Driver
(Note 7)
6V < V
IN
< 38V
I
CC
= 0mA to 20mA
EXTV
CC
Ramping Positive
I
CC
= 20mA, V
EXTVCC
= 5V
l
MIN
TYP
1.4
25
25
25
25
30
30
90
MAX
UNITS
Ω
ns
ns
ns
ns
ns
ns
ns
INTV
CC
Linear Regulator
4.8
4.5
5.0
0.5
4.7
50
200
500
250
770
250
7.5
0.1
8.5
0.3
±2
550
290
880
100
5.2
2
V
%
V
mV
mV
kHz
kHz
kHz
kΩ
μA
V
μA
Oscillator and Phase-Locked Loop
R
MODE/PLLIN
MODE/PLLIN Input Resistance
PGOOD OUTPUT
–7
7
–10
10
100
–12.5
12.5
%
%
μs
t
PG
PGOOD Bad Blanking Time
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 LTC3865/LTC3865-1 are tested under pulsed load conditions
such that T
J
≈ T
A
. The LTC3865E/LTC3865E-1 are guaranteed to meet
performance specifications over the 0°C to 85°C operating junction
temperature range. Specifications over the –40°C to 125°C operating
junction temperature range are assured by design, characterization and
correlation with statistical process controls. The LTC3865I/LTC3865I-1
are guaranteed to meet performance specifications over the full –40°C
to 125°C operating junction temperature range. Note that the maximum
ambient temperature consistent with these specifications is determined by
specific operating conditions in conjunction with board layout, the rated
package thermal resistance and other environmental factors.
Note 3:
T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
according to the following formulas:
LTC3865UH: T
J
= T
A
+ (P
D
• 34°C/W)
LTC3865FE: T
J
= T
A
+ (P
D
• 25°C/W)
Note 4:
The LTC3865/LTC3865-1 are tested in a feedback loop that servos
V
ITH1,2
to a specified voltage and measures the resultant V
OSENSE1,2
.
Note 5:
Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency. See Applications Information.
Note 6:
Rise and fall times are measured using 10% and 90% levels. Delay
times are measured using 50% levels.
Note 7:
The minimum on-time condition is specified for an inductor peak-
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