that drives all N-channel power MOSFETs. The controlled
on-time, valley current mode control architecture allows for
fast transient response and constant frequency switching
in steady-state operation, independent of V
IN
, V
OUT
and
load current. Its load-release transient detection feature
significantly reduces overshoot at low output voltages.
Differential output voltage sensing, along with a preci-
sion internal reference, offers an accurate ±0.67% output
regulation, even if the remote output ground deviates from
local ground by ±500mV.
The switching frequency can be programmed from 200kHz
to 2MHz with an external resistor and can be synchronized
to an external clock. Very low t
ON
and t
OFF
times allow for
near 0% and near 100% duty cycles, respectively. Volt-
age tracking soft start-up and multiple safety features are
provided.
L,
LT, LTC, LTM, PolyPhase, OPTI-LOOP Linear Technology and the Linear logo are
,
registered trademarks and Hot Swap and Stage Shedding are trademarks of Linear Technology
Corporation. All other trademarks are the property of their respective owners. Protected by U.S.
Patents, including 5481178, 5847554, 6580258, 6304066, 6476589, 6774611.
n
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Wide V
IN
Range: 4.5V to 38V, V
OUT
: 0.6V to 5.5V
±0.67% Output Voltage Accuracy Over Temperature,
Differential Output Voltage Sensing, Allowing Up to
±500mV Line Loss at Remote Ground
Controlled On-Time, Valley Current Mode Control
Fast Load Transient Response
Detect Transient (DTR) Reduces V
OUT
Overshoot
Frequency Programmable from 200kHz to 2MHz,
Synchronizable to External Clock
t
ON(MIN)
= 30ns, t
OFF(MIN)
= 90ns
Up to 12-Phase Operation
R
SENSE
or Inductor DCR Current Sensing
Overvoltage Protection and Current Limit Foldback
Power Good Output Voltage Monitor
Output Voltage Tracking and Adjustable Soft Start-Up
Thermally Enhanced 32-Pin (5mm
×
5mm) QFN
Package
APPLICATIONS
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Distributed Power Systems
Point-of-Load Converters
Computing Systems
Data Communication Systems
TYPICAL APPLICATION
3.3V/25A Output, 2MHz Step-Down Converter (Refer to Figure 20 for Full Design)
V
IN
4.5V TO 14V
SENSE1
–
SENSE1
+
V
IN
TG1
V
OUT
3.3V
25A
100µF
×6
0.3µH
SW1
0.1µF
LTC3839
SENSE2
–
SENSE2
+
INTV
CC
TG2
SW2
0.1µF
EFFICIENCY (%)
0.3µH
90
80
100
DISCONTINUOUS
MODE
Efficiency/Power Loss
V
IN
= 5V
10
8
POWER LOSS (W)
BOOST1
BOOST2
DRV
CC2
BG2
FORCED
CONTINUOUS
MODE
6
+
45.3k
10k
DRV
CC1
4.7µF
BG1
PGND
V
OUTSENSE+
V
OUTSENSE–
TRACK/SS
ITH
RT
SGND
70
4
2
LOSS
DCM
0
100
3839 TA01b
60
MODE/PLLIN
CLKOUT
PHASMD
RUN
DTR
50
0.1
LOSS
FORCED CM
1
10
LOAD CURRENT (A)
18.7k
3839 TA01a
3839fa
1
LTC3839
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
SENSE2
+
SENSE2
–
BOOST2
SGND
V
RNG
SW2
24 BG2
23 DRV
CC2
22 EXTV
CC
33
PGND
21 INTV
CC
20 PGND
19 V
IN
18 DRV
CC1
17 BG1
9 10 11 12 13 14 15 16
V
OUTSENSE–
DTR
PGOOD
BOOST1
SENSE1
+
SENSE1
–
SW1
TG1
RUN
TG2
V
IN
Voltage ................................................. –0.3V to 40V
BOOST1, BOOST2 Voltages ....................... –0.3V to 46V
SW1, SW2 Voltages ...................................... –5V to 40V
INTV
CC
, DRV
CC1
, DRV
CC2
, EXTV
CC
, PGOOD, RUN,
(BOOST1-SW1), (BOOST2-SW2), MODE/PLLIN
Voltages ....................................................... –0.3V to 6V
V
OUTSENSE+
, V
OUTSENSE–
, SENSE1
+
, SENSE2
+
,
SENSE1
–
, SENSE2
–
Voltages ....................... –0.6V to 6V
TRACK/SS Voltage ....................................... –0.3V to 5V
DTR, PHASMD, RT, V
RNG
,
ITH Voltages ........................... –0.3V to (INTV
CC
+ 0.3V)
Operating Junction Temperature Range
(Notes 2, 3, 4) ........................................ –40°C to 125°C
Storage Temperature Range .................. –65°C to 150°C
32 31 30 29 28 27 26 25
PHASMD 1
MODE/PLLIN 2
CLKOUT 3
SGND 4
RT 5
ITH 6
TRACK/SS 7
V
OUTSENSE
+
8
UH PACKAGE
32-LEAD (5mm
×
5mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 44°C/W
EXPOSED PAD (PIN 33) IS PGND, MUST BE SOLDERED TO PCB
(http://www.linear.com/product/LTC3839#orderinfo)
LEAD FREE FINISH
LTC3839EUH#PBF
LTC3839IUH#PBF
TAPE AND REEL
LTC3839EUH#TRPBF
LTC3839IUH#TRPBF
PART MARKING*
3839
3839
PACKAGE DESCRIPTION
32-Lead (5mm
×
5mm) Plastic QFN
32-Lead (5mm
×
5mm) Plastic QFN
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
ORDER INFORMATION
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.
Comparison of LTC3839 and LTC3838 Options
PART NUMBER
LTC3839
LTC3838
LTC3838-1
LTC3838-2
DESCRIPTION
Single Output, ±0.67% Differential Output Regulation, Continuous 30mV to 100mV Current Sense Range Control
Dual or Single Output, ±0.67% Differential Output Regulation on Channel 1, ±1% Output Regulation on Channel 2,
Separate-Per-Channel Continuous 30mV to 100mV Current Sense Range Controls
Dual or Single Output, ±0.67% and ±0.75% Output Regulation on Channel 1 and 2, Both Channels Differential, Single-Pin
30mV/60mV Current Sense Range Control, Improved Current Limit Accuracy than LTC3838 and LTC3839
Dual Output (Internal Reference on Channel 1, External Reference on Channel 2) or Single Output (External Reference),
±0.67% Differential Output Regulation with Internal Reference on Channel 1, 0.6V ≤ V
OUT
≤ 5.5V ±4mV Differential
Output Regulation with External Reference Voltage on Channel 2, 0.4V ≤ V
OUT2
≤ 5.5V, Fixed 30mV Current Sense Range,
Improved Current Limit Accuracy than LTC3838 and LTC3839
2
3839fa
LTC3839
ELECTRICAL CHARACTERISTICS
SYMBOL
V
IN
V
OUT(REG)
I
Q
PARAMETER
Input Voltage Operating Range
Regulated Output Voltage Operating Range V
OUT
Regulated Differentially with Respect to
V
OUTSENSE–
Input DC Supply Current
RUN Enabled
Shutdown Supply Current
MODE/PLLIN = 0V, No Load
RUN = 0V
ITH1 = 1.2V (Note 5)
T
A
= 25°C
T
A
= 0°C to 85°C
T
A
= –40°C to 125°C
V
IN
= 4.5V to 38V, ITH1 = 0.5V to 1.9V
–0.5V < V
OUTSENSE–
< 0.5V (Notes 5, 7)
V
OUTSENSE+
– V
OUTSENSE–
= 0.6V
V
OUTSENSE+
– V
OUTSENSE–
= 0.6V
ITH = 1.2V (Note 5)
V
IN
= 38V, V
OUT
= 0.6V, R
T
= 20k (Note 6)
(Note 6)
V
RNG
= 2V, V
FB
= 0.57V, V
SENSE–
= 2.5V
V
RNG
= 0V, V
FB
= 0.57V, V
SENSE–
= 2.5V
V
RNG
= INTV
CC
, V
FB
= 0.57V, V
SENSE–
= 2.5V
V
RNG
= 2V, V
FB
= 0.63V, V
SENSE–
= 2.5V
V
RNG
= 0V, V
FB
= 0.63V, V
SENSE–
= 2.5V
V
RNG
= INTV
CC
, V
FB
= 0.63V, V
SENSE–
= 2.5V
V
SENSE+
= 0.6V
V
SENSE+
= 5V
V
SENSE–
= 0.6V
V
SENSE–
= 5V
V
RUN
Rising
V
RUN
Falling from On Threshold
RUN = SGND
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. V
IN
= 15V unless otherwise noted (Note 3).
CONDITIONS
MIN
4.5
0.6
TYP
MAX
38
5.5
UNITS
V
V
Main Control Loops
3
15
0.5985
0.596
0.594
0.591
0.6
0.6
0.6
0.6
±5
–25
1.7
30
90
80
21
39
100
30
50
–50
–15
–25
±5
1
1.2
10
1.1
1.2
100
2.5
10
1.3
±50
±2
120
40
61
0.6015
0.604
0.606
0.609
±25
–50
mA
µA
V
V
V
V
nA
µA
mS
ns
ns
mV
mV
mV
mV
mV
mV
nA
µA
µA
µA
V
mV
µA
µA
V
V
µA
kHz
kHz
kHz
Deg
Deg
Deg
Deg
Deg
Deg
V
3839fa
V
OUTSENSE(REG)
Regulated Differential Feedback Voltage
(V
OUTSENSE+
– V
OUTSENSE–
)
Regulated Differential Feedback Voltage
Over Line, Load and Common Mode
I
VOUTSENSE+
I
VOUTSENSE–
g
m(EA)
t
ON(MIN)1,2
t
OFF(MIN)1,2
Current Sensing
V
SENSE(MAX)1,2
Maximum Valley Current Sense Threshold
(V
SENSE1,2+
– V
SENSE1,2–
)
V
SENSE(MIN)1,2
I
SENSE1,2+
I
SENSE1,2–
Minimum Valley Current Sense Threshold
(V
SENSE1,2+
– V
SENSE1,2–
)
(Forced Continuous Mode)
SENSE1,2
+
Pins Input Bias Current
SENSE1,2
–
Pins Input Bias Current
(Internal 500k Resistor to SGND)
RUN Pin On Threshold
RUN Pin On Hysteresis
I
RUN
RUN Pin Pull-Up Current when Off
RUN Pin Pull-Up Current Hysteresis
(I
RUN(ON)
– I
RUN(OFF)
)
UVLO
I
TRACK/SS
f
INTV
CC
Undervoltage Lockout
Soft-Start Pull-Up Current
Clock Output Frequency
(Steady-State Switching Frequency)
Channel 2 Phase (Relative to Channel 1)
V
OUTSENSE+
Input Bias Current
V
OUTSENSE–
Input Bias Current
Error Amplifier Transconductance
Minimum Top Gate On-Time
Minimum Top Gate Off-Time
l
l
l
Start-Up and Shutdown
V
RUN
INTV
CC
Falling
INTV
CC
Rising
0V < TRACK/SS < 0.6V
R
T
= 205k
R
T
= 80.6k
R
T
= 18.2k
PHASMD = SGND
PHASMD = Floating
PHASMD = INTV
CC
PHASMD = SGND
PHASMD = Floating
PHASMD = INTV
CC
l
l
3.3
3.7
4.2
1
200
500
2000
180
180
240
60
90
120
4.5
Frequency and Clock Synchronization
450
550
CLKOUT Phase (Relative to Channel 1)
V
PLLIN(H)
Clock Input High Level Into MODE/PLLIN
2
3
LTC3839
ELECTRICAL CHARACTERISTICS
SYMBOL
V
PLLIN(L)
R
MODE/PLLIN
Gate Drivers
R
TG(UP)1,2
R
TG(DOWN)1,2
R
BG(UP)1,2
R
BG(DOWN)1,2
t
D(TG/BG)1,2
t
D(BG/TG)1,2
V
DRVCC1
V
EXTVCC
TG Driver Pull-Up On Resistance
TG Driver Pull-Down On Resistance
BG Driver Pull-Up On Resistance
BG Driver Pull-Down On Resistance
TG High
TG Low
BG High
BG Low
2.5
1.2
2.5
0.8
20
15
5.0
4.4
5.3
–1.5
4.6
200
200
5
–5
7.5
–7.5
2
0.1
50
20
0.3
10
–10
5.6
–3.5
4.8
Ω
Ω
Ω
Ω
ns
ns
V
%
V
mV
mV
%
%
%
V
µs
µs
PARAMETER
Clock Input Low Level Into MODE/PLLIN
MODE/PLLIN Input Resistance
With Respect to SGND
600
The
l
denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 15V unless otherwise noted (Note 3).
CONDITIONS
MIN
TYP
MAX
0.5
UNITS
V
kΩ
Top Gate Off to Bottom Gate On Delay Time (Note 6)
Bottom Gate Off to Top Gate On Delay Time (Note 6)
Internally Regulated DRV
CC1
Voltage
DRV
CC1
Load Regulation
EXTV
CC
Switchover Voltage
EXTV
CC
Switchover Hysteresis
EXTV
CC
to DRV
CC2
Voltage Drop
6V < V
IN
< 38V
I
DRVCC1
= 0mA to –100mA
EXTV
CC
Rising
EXTV
CC
Falling from Switchover Voltage
V
EXTVCC
= 5V, I
DRVCC2
= –100mA
V
OUT
Rising, with Respect to Regulated Voltage
V
OUT
Falling, with Respect to Regulated Voltage
V
OUT
Returning to Reference Voltage
I
PGOOD
= 2mA
Internal V
CC
Regulator
PGood Output
OV
UV
V
PGOOD(L)
t
D(PGOOD)
PGOOD Overvoltage Threshold
PGOOD Undervoltage Threshold
PGOOD Threshold Hysteresis
PGOOD Low Voltage
Delay from V
FB
Fault (OV/UV) to PGOOD
Falling
Delay from V
FB
Good to PGOOD Rising
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 junction temperature (T
J
, in °C) is calculated from the ambient
temperature (T
A
, in °C) and power dissipation (P
D
, in Watts) according to
the formula:
T
J
= T
A
+ (P
D
•
θ
JA
)
where
θ
JA
(in °C/W) is the package thermal impedance.
Note 3:
The LTC3839 is tested under pulsed loading conditions such that
T
J
≈ T
A
. The LTC3839E is guaranteed to meet 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 LTC3839I is guaranteed to meet specifications over the –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 impedance and other environmental factors.
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 specified absolute maximum operating
junction temperature may impair device reliability or permanently damage
the device.
Note 5:
The LTC3839 is tested in a feedback loop that adjusts the
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