High Efficiency, 1.5V/30A Step-Down Converter with Very Low DCR Sensing
100k
0.1µF
FREQ
RUN
TK/SS
ITH
V
FB
DIFFP
30.1k
220pF
20k
10k
1.5nF
C1
220nF
C2
220nF
DIFFN
SNSD
+
SNS
–
SNSA
+
ILIM
DIFFOUT
LTC3866
MODE/PLLIN
PGOOD
ITEMP
EXTV
CC
INTV
CC
BOOST
TG
SW
BG
PGND
CLKOUT
SGND
R2
931
R1
4.64k
V
IN
0.1µF
0.33µH
DCR = 0.32m
C
OUT
470µF
×2
V
OUT
1.5V
30A
220µF
4.7µF
V
IN
4.5V TO 20V
Efficiency vs Load Current
and Mode
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0.01
0.1
V
IN
= 12V
V
OUT
= 1.5V
L = 0.33µH
(DCR = 0.32m TYP)
CCM
PULSE SKIPPING
Burst Mode
OPERATION
1
10
LOAD CURRENT (A)
100
3866 TA01b
3866 TA01a
3866fc
For more information
www.linear.com/LTC3866
1
LTC3866
absoluTe MaxiMuM raTings
(Note 1)
Input Supply Voltage .................................. –0.3V to 40V
Topside Driver Voltage (BOOST) ................ –0.3V to 46V
Switch Voltage(SW) ..................................... –5V to 40V
INTV
CC
, EXTV
CC
, RUN, PGOOD,
BOOST-SW Voltages .................................... –0.3V to 6V
SNSD
+
, SNSA
+
, SNS
–
Voltages ............. –0.3V to INTV
CC
MODE/PLLIN, ILIM, TK/SS, FREQ,
DIFFOUT Voltages ................................. –0.3V to INTV
CC
DIFFP, DIFFN ......................................... –0.3V to INTV
CC
ITEMP, ITH, V
FB
Voltages .................... –0.3V to INTV
CC
INTV
CC
Peak Output Current ..............................100mA
Operating Junction Temperature Range
(Notes 2, 4) ............................................ –40°C to 125°C
Storage Temperature Range .................. –65°C to 125°C
Lead Temperature (Soldering, 10 sec)
FE Package ....................................................... 300°C
pin conFiguraTion
TOP VIEW
FREQ
RUN
TK/SS
ITH
V
FB
DIFFOUT
DIFFN
DIFFP
SNSD
+
1
2
3
4
5
6
7
8
9
25
SGND
24 MODE/PLLIN
22 ITEMP
21 EXTV
CC
20 V
IN
19 INTV
CC
18 BOOST
17 TG
16 SW
15 BG
14 PGND
13 CLKOUT
ITH 1
V
FB
2
DIFFOUT 3
DIFFN 4
DIFFP 5
SNSD
+
TOP VIEW
MODE/PLLIN
PGOOD
24 23 22 21 20 19
18 EXTV
CC
17 V
IN
25
SGND
16 INTV
CC
15 BOOST
14 TG
13 SW
7
SNS
–
8
SNSA
+
9 10 11 12
ILIM
PGND
CLKOUT
BG
SNS
–
10
SNSA
+
11
ILIM 12
6
FE PACKAGE
24-LEAD PLASTIC TSSOP
θ
JA
= 33°C/W,
θ
JC
= 10°C/W
EXPOSED PAD (PIN 25) IS SGND, MUST BE SOLDERED TO PCB
UF PACKAGE
24-LEAD (4mm
×
4mm) PLASTIC QFN
θ
JA
= 47°C/W,
θ
JC
= 4.5°C/W
EXPOSED PAD (PIN 25) IS SGND, MUST BE SOLDERED TO PCB
orDer inForMaTion
LEAD FREE FINISH
LTC3866EFE#PBF
LTC3866IFE#PBF
LTC3866EUF#PBF
LTC3866IUF#PBF
TAPE AND REEL
LTC3866EFE#TRPBF
LTC3866IFE#TRPBF
LTC3866EUF#TRPBF
LTC3866IUF#TRPBF
http://www.linear.com/product/LTC3866#orderinfo
PART MARKING*
LTC3866FE
LTC3866FE
3866
3866
PACKAGE DESCRIPTION
24-Lead Plastic TSSOP
24-Lead Plastic TSSOP
24-Lead (4mm
×
4mm) Plastic QFN
24-Lead (4mm
×
4mm) Plastic QFN
TEMPERATURE RANGE
–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.
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/.
Some packages are available in 500 unit reels through
designated sales channels with #TRMPBF suffix.
FREQ
RUN
23 PGOOD
ITEMP
TK/SS
2
3866fc
For more information
www.linear.com/LTC3866
LTC3866
elecTrical characTerisTics
SYMBOL
V
IN
V
OUT
V
FB
I
FB
V
REFLNREG
V
LOADREG
g
m
I
Q
UVLO
UVLO
HYS
V
FBOVL
I
SNSD
+
I
SNSA
+
A
VT_SNS
PARAMETER
Input Voltage Range
Output Voltage Range
Regulated Feedback Voltage
with Diffamp in Loop
Current ITH Voltage = 1.2V (Note 5)
–40°C to 85°C
–40°C to 125°C
(Note 5)
V
IN
= 4.5V to 38V (Note 5)
(Note 5)
Measured in Servo Loop;
∆ITH
Voltage = 1.2V to 0.7V
Measured in Servo Loop;
∆ITH
Voltage = 1.2V to 1.6V
ITH =1.2V, Sink/Source 5µA (Note 5)
(Note 6)
V
IN
= 15V
V
IN
= 15V, V
RUN
= 0V
V
INTVCC
Ramping Down
l
l
l
l
l
The
l
denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at T
A
= 25°C (Note 2). V
IN
= 15V, V
RUN
= 5V unless otherwise specified.
CONDITIONS
MIN
4.5
0.6
0.597
0.5955
0.6
0.6
–15
0.002
TYP
MAX
38
3.5
0.603
0.6045
–50
0.02
UNITS
V
V
V
V
nA
%
Main Control Loops
Feedback Current
Reference Voltage Line
Regulation
Output Voltage Load
Regulation
Error Amplifier (EA)
Transconductance
Input DC Supply Current
Normal Mode
Shutdown
Undervoltage Lockout
UVLO Hysteresis Voltage
l
l
0.01
0.01
2
0.1
0.1
%
%
mmho
3.2
30
3.4
0.64
3.75
0.5
0.66
30
1
5
50
4.1
0.68
100
2
mA
µA
V
V
V
nA
µA
V/V
Feedback Overvoltage Lockout Measured at V
FB
SNSD
+
Pin Bias Current
SNSA
+
Pin Bias Current
Total Sense Signal Gain to
Current Comparator
V
SNSD
+ = 3.3V
V
SNSA
+ = 3.3V
(V
SNSD
+ + V
SNSA
+)/V
SNSD
+
–40°C to 85°C
V
SNS
– = 1.8V, ILIM = 0V
ILIM = 1/4 V
INTVCC
ILIM = 1/2 V
INTVCC
or Float
ILIM = 3/4 V
INTVCC
ILIM = V
INTVCC
–40°C to 125°C
V
SNS
– = 1.8V, ILIM = 0V
ILIM = 1/4V
INTVCC
ILIM = 1/2V
INTVCC
or Float
ILIM = 3/4V
INTVCC
ILIM = V
INTVCC
V
ITEMP
= 0.3V
V
TK/SS
= 0V
V
SENSE(MAX)
Maximum Current Sense
Threshold
l
l
l
l
l
l
l
l
l
l
l
l
l
9.2
14.2
19.2
23.5
28.5
9
14
19
23.5
28.5
9
1.0
1.1
10
15
20
25
30
10
15
20
25
30
10
1.25
1.22
80
10.8
15.8
20.8
26.5
31.5
11
16
21
26.5
31.5
11
1.5
1.35
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
µA
µA
V
mV
I
TEMP
I
TK/SS
V
RUN
V
RUN(HYS)
TG
t
r
t
f
t
r
t
f
DCR Temperature
Compensation Current
Soft-Start Charge Current
RUN Pin On Hysteresis
Voltage
Top Gate (TG) Transition Time
Rise Time
Fall Time
Bottom Gate (BG) Transition
Time
Rise Time
Fall Time
RUN Pin On Threshold Voltage V
RUN
Rising
(Note 7)
C
LOAD
= 3300pF
C
LOAD
= 3300pF
(Note 7)
C
LOAD
= 3300pF
C
LOAD
= 3300pF
25
25
ns
ns
BG
25
25
ns
ns
3866fc
For more information
www.linear.com/LTC3866
3
LTC3866
elecTrical characTerisTics
SYMBOL
TG/BG t
D
BG/TG t
D
t
ON(MIN)
V
INTVCC
V
EXTVCC
PARAMETER
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
Load Regulation
External V
CC
Switchover
Voltage
EXTV
CC
Voltage Drop
EXTV
CC
Hysteresis
Oscillator and Phase-Locked Loop
f
NOM
f
LOW
f
HIGH
I
FREQ
CLKOUT
CLKOUT
HI
CLKOUT
LO
V
PGDLO
I
PGD
V
PGD
Nominal Frequency
Lowest Frequency
Highest Frequency
Frequency Setting Current
Phase Relative to the
Oscillator Clock
Clock Output High Voltage
Clock Output Low Voltage
PGOOD Voltage Low
PGOOD Leakage Current
PGOOD Trip
I
PGOOD
= 2mA
V
PGOOD
= 5.5V
V
FB
with Respect to Set Output Voltage
V
FB
Going Negative
V
FB
Going Positive
–40°C to 85°C
–40°C to 125°C
Measured at DIFFP Input
V
DIFFP
= 1.5V, V
DIFFOUT
= 100µA
5V < V
IN
< 38V
1.5
V
INTVCC
= 5.5V, I
DIFFOUT
= 300µA
(Note 9)
(Note 9)
90
3
l
l
The
l
denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at T
A
= 25°C (Note 2). V
IN
= 15V, V
RUN
= 5V unless otherwise specified.
CONDITIONS
C
LOAD
= 3300pF
C
LOAD
= 3300pF
(Note 8)
6V < V
IN
< 38V
I
INTVCC
= 0mA to 20mA
EXTV
CC
Ramping Positive
I
EXTVCC
= 20mA, V
EXTVCC
= 5V
4.5
5.25
MIN
TYP
30
MAX
UNITS
ns
30
ns
90
5.5
0.5
4.7
50
200
100
5.75
2
ns
V
%
V
mV
mV
550
275
850
11
kHz
kHz
kHz
kΩ
µA
Deg
V
0.2
0.3
2
V
V
µA
%
%
1.001
1.002
2
V/V
V/V
kΩ
mV
dB
mA
V
MHz
V/µs
INTV
CC
Linear Regulator
V
FREQ
= 1.2V
V
FREQ
= 0.4V
V
FREQ
> 2.4V
450
225
700
9
500
250
770
250
10
180
R
MODE/PLLIN
MODE/PLLIN Input Resistance
V
INTVCC
= 5.5V
4.5
5.5
0
0.1
PGOOD Output
–10
10
0.999
0.998
1
1
80
Differential Amplifier
A
V
R
IN
V
OS
PSRR
I
OUT
V
OUT
GBW
SR
Gain
Input Resistance
Input Offset Voltage
Power Supply Rejection Ratio
Maximum Sourcing Output
Current
Maximum Output Voltage
Gain-Bandwidth Product
Slew Rate
V
INTVCC
– 1.4 V
INTVCC
– 1.1
3
2
4
3866fc
For more information
www.linear.com/LTC3866
LTC3866
elecTrical characTerisTics
SYMBOL
TG R
UP
TG R
DOWN
BG R
UP
BG R
DOWN
PARAMETER
TG Pull-Up R
DS(ON)
TG Pull-Down R
DS(ON)
BG Pull-Up R
DS(ON)
BG Pull-Down R
DS(ON)
CONDITIONS
TG High
TG Low
BG High
BG Low
On-Chip Driver
2.6
1.5
2.4
1.1
Ω
Ω
Ω
Ω
The
l
denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at T
A
= 25°C (Note 2). V
IN
= 15V, V
RUN
= 5V unless otherwise specified.
MIN
TYP
MAX
UNITS
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 LTC3866 is tested under pulsed load conditions such that
T
J
≈ T
A
. The LTC3866E is guaranteed to meet performance specifications
from 0°C to 85°C operating 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 LTC3866I is guaranteed to meet performance specifications over the
full –40°C to 125°C operating junction temperature range. The maximum
ambient temperature consistent with these specifications is determined
by specific operating conditions in conjunction with board layout, the
package thermal impedance and other environmental factors.
Note 3:
The junction temperature, T
J
, is calculated from the ambient
temperature, T
A
, and power dissipation, P
D
, according to the following
formula:
LTC3866FE: T
J
= T
A
+ (P
D
• 33°C/W)
LTC3866UF: T
J
= T
A
+ (P
D
• 47°C/W)
Note 4:
This IC includes overtemperature protection that is intended to
protect the device during momentary overload conditions. The maximum
rated junction temperature will be exceeded when this protection is active.
Continuous operation above the absolute maximum operating junction
temperature may impair device reliability or permanently damage the
device.
Note 5:
The LTC3866 is tested in a feedback loop that servos V
ITH
to a
specified voltage and measures the resultant V
FB
.
Note 6:
Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency. See Applications Information.
Note 7:
Rise and fall times are measured using 10% and 90% levels. Delay
times are measured using 50% levels.
Note 8:
The minimum on-time condition corresponds to the on inductor
peak-to-peak ripple current ≥40% of I
MAX
(see Minimum On-Time
Considerations in the Applications Information section).
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