FEATURES
s
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LTC3729L-6
PolyPhase, Synchronous
Step-Down Switching Regulator
DESCRIPTIO
The LTC
®
3729L-6 is a PolyPhase
TM
synchronous step
-
down current mode switching regulator controller with a
0.6V reference that drives N-channel external power
MOSFET stages in a phase-lockable fixed frequency archi-
tecture. The PolyPhase controller drives its two output
stages out of phase at frequencies up to 550kHz to
minimize the RMS ripple currents in both input and output
capacitors. The output clock signal allows expansion for
up to 12 evenly phased controllers for systems requiring
15A to 200A of output current. This PolyPhase technique
effectively multiplies the fundamental frequency by the
number of channels used, improving transient response
while operating each channel at an optimum frequency for
efficiency. Thermal design is also simplified.
An internal differential amplifier provides true remote
sensing of the regulated supply’s positive and negative
output terminals as required for high current applications.
A RUN/SS pin provides both soft-start and optional timed,
short-circuit shutdown. Current foldback limits MOSFET
dissipation during short-circuit conditions when the
overcurrent latchoff is disabled. OPTI-LOOP compensa-
tion allows the transient response to be optimized over a
wide range of output capacitance and ESR values. The
LTC3729L-6 includes a power good output pin that
indicates when the output voltage is inside the
±10%
tolerance window.
s
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Reduces Required Input Capacitance and Power
Supply Induced Noise
True Remote Sensing Differential Amplifier
0.6V,
±
1% Voltage Reference Accuracy
PolyPhase Controller Operates from Two to Twelve
Phases
Current Mode Control Ensures Current Sharing
Phase-Lockable Fixed Frequency: 250kHz to 550kHz
OPTI-LOOP
®
Compensation Reduces C
OUT
Power Good Output Voltage Monitor
Wide V
IN
Range: 4V to 30V Operation
Very Low Dropout Operation: 99% Duty Cycle
Adjustable Soft-Start Current Ramping
Internal Current Foldback Plus Shutdown Timer
Overvoltage Soft-Latch Eliminates Nuisance Trips
Micropower Shutdown
32-Lead 5mm
×
5mm Plastic QFN Package
APPLICATIO S
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Desktop Computers
Internet Servers
Large Memory Arrays
DC Power Distribution Systems
, LTC and LT are registered trademarks of Linear Technology Corporation.
OPTI-LOOP is a registered trademark of Linear Technology Corporation.
PolyPhase is a trademark of Linear Technology Corporation.
TYPICAL APPLICATIO
0.1µF
S
10Ω
10µF
×6
35V
CERAMIC
L1
1µH
D1
V
IN
LTC3729L-6 TG1
BOOST1
SW1
M1
S
0.1µF
RUN/SS
3300pF
PGOOD
I
TH
1.5k
S
0.47µF
S
BG1
PGND
SENSE1
+
SENSE1
–
TG2
BOOST2
SW2
S
S
M2
×2
CLKOUT
SGND
10k
V
DIFFOUT
S
M3
S
0.47µF
M4
×2
D2
L2
1µH
0.002Ω
BG2
INTV
CC
SENSE2
+
SENSE2
–
S
EAIN
V
OS –
V
OS
+
60.4k
10µF CER
X5R
C
OUT
: T510E108K004AS
D1, D2: SBM540
L1, L2: CEPH149-IROMC-H
M1, M3: Si7840DP
M2, M4: Si7440DP
Figure 1. High Current Dual Phase Step-Down Converter
U
U
U
V
IN
5V TO 15V
0.002Ω
V
OUT
0.7V/40A
+
C
OUT
270µF
×4
2V
3729L-6
TA01
sn3729l6 3729l6fs
1
LTC3729L-6
ABSOLUTE
AXI U RATI GS
Input Supply Voltage (V
IN
).........................30V to – 0.3V
Topside Driver Voltages (BOOST1,2) .........36V to – 0.3V
Switch Voltage (SW1, 2) .............................30V to – 5 V
SENSE1
+
, SENSE2
+
, SENSE1
–
,
SENSE2
–
Voltages ........................ (1.1)INTV
CC
to – 0.3V
EAIN, V
OS+
, V
OS–
, EXTV
CC
, INTV
CC
,
RUN/SS, PGOOD Voltages ...........................7V to – 0.3V
Boosted Driver Voltage (BOOST-SW) ..........7V to – 0.3V
PLLFLTR, PLLIN, CLKOUT, PHASMD,
V
DIFFOUT
Voltages ................................ INTV
CC
to – 0.3V
PACKAGE/ORDER I FOR ATIO
TOP VIEW
SENSE1
–
SENSE1
+
CLKOUT
RUN/SS
SW1
TG1
NC
NC
32 31 30 29 28 27 26 25
EAIN 1
PLLFLTR 2
PLLIN 3
PHASMD 4
I
TH
5
SGND 6
V
DIFFOUT
7
V
OS –
8
9 10 11 12 13 14 15 16
24 BOOST1
23 V
IN
22 BG1
21 EXTV
CC
20 INTV
CC
19 PGND
18 BG2
17 BOOST2
SENSE2
–
SENSE2
+
V
OS +
PGOOD
TG2
SW2
NC
NC
UH PACKAGE
32-LEAD (5mm
×
5mm) PLASTIC QFN
EXPOSED PAD IS SIGNAL GROUND
(MUST BE SOLDERED TO PCB)
T
JMAX
= 125°C,
θ
JA
= 34°C/W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
SYMBOL
V
EAIN
V
SENSEMAX
I
INEAIN
PARAMETER
Regulated Feedback Voltage
Maximum Current Sense Threshold
Feedback Current
Main Control Loop
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 15V, V
RUN/SS
= 5V unless otherwise noted.
CONDITIONS
(Note 3); I
TH
Voltage = 1.2V
V
SENSE –
= 5V
(Note 3)
q
q
2
U
U
W
W W
U
W
(Note 1)
I
TH
Voltage ................................................2.7V to – 0.3V
Peak Output Current <1µs (TGL1,2, BG1,2)............... 3A
INTV
CC
RMS Output Current ................................ 40mA
Operating Ambient Temperature Range
LTC3729LEUH-6 (Note 6) ..................... – 40°C to 85°C
Junction Temperature (Note 2) ............................. 125°C
Storage Temperature Range ................. – 65°C to 125°C
Reflow Peak Body Temperature ............................ 240°C
ORDER PART
NUMBER
LTC3729LEUH-6
UH PART
MARKING
3729L6
MIN
0.594
62
65
TYP
0.600
75
75
–5
MAX
0.606
88
85
– 50
UNITS
V
mV
mV
nA
sn3729l6 3729l6fs
LTC3729L-6
ELECTRICAL CHARACTERISTICS
SYMBOL
V
LOADREG
PARAMETER
Output Voltage Load Regulation
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 15V, V
RUN/SS
= 5V unless otherwise noted.
CONDITIONS
(Note 3)
Measured in Servo Loop; I
TH
Voltage = 0.7V
Measured in Servo Loop; I
TH
Voltage = 2V
V
IN
= 3.6V to 30V (Note 3)
Measured at V
EAIN
V
IN
Ramping Down
I
TH
= 1.2V; Sink/Source 5µA; (Note 3)
I
TH
= 1.2V; (g
m
xZ
L
; No Ext Load); (Note 3)
(Note 4)
EXTV
CC
Tied to V
OUT
; V
OUT
= 5V
V
RUN/SS
= 0V
V
RUN/SS
= 1.9V
V
RUN/SS
Rising
V
RUN/SS
Rising from 3V
Soft Short Condition V
EAIN
= 0.375V; V
RUN/SS
= 4.5V
V
EAIN
= 0.4V
Each Channel; V
SENSE1
–
, 2
– = V
SENSE1
+
, 2
+ = 0V
In Dropout; V
SENSEMAX
≤
30mV
C
LOAD
= 3300pF
C
LOAD
= 3300pF
C
LOAD
= 3300pF
C
LOAD
= 3300pF
C
LOAD
= 3300pF Each Driver
C
LOAD
= 3300pF Each Driver
Tested with a Square Wave (Note 5)
6V < V
IN
< 30V; V
EXTVCC
= 4V
I
CC
= 0 to 20mA; V
EXTVCC
= 4V
I
CC
= 20mA; V
EXTVCC
= 5V
I
CC
= 20mA, EXTV
CC
Ramping Positive
I
CC
= 20mA, EXTV
CC
Ramping Negative
V
PLLFLTR
= 1.2V
V
PLLFLTR
= 0V
V
PLLFLTR
≥
2.4V
360
230
480
q
q
q
q
MIN
TYP
0.1
– 0.1
0.002
MAX
0.5
– 0.5
0.02
0.68
4
UNITS
%
%
%/V
V
V
mmho
V/mV
µA
µA
µA
V
V
µA
µA
µA
%
V
REFLNREG
V
OVL
UVLO
g
m
g
mOL
I
Q
Reference Voltage Line Regulation
Output Overvoltage Threshold
Undervoltage Lockout
Transconductance Amplifier g
m
Transconductance Amplifier Gain
Input DC Supply Current
Normal Mode
Shutdown
Soft-Start Charge Current
RUN/SS Pin ON Threshold
RUN/SS Pin Latchoff Arming
RUN/SS Discharge Current
Shutdown Latch Disable Current
Total Sense Pins Source Current
Maximum Duty Factor
Top Gate Transition Time:
Rise Time
Fall Time
Bottom Gate 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
Voltage Drop
EXTV
CC
Switchover Voltage
EXTV
CC
Switchover Hysteresis
Nominal Frequency
Lowest Frequency
Highest Frequency
PLLIN Input Resistance
Phase Detector Output Current
Sinking Capability
Sourcing Capability
0.64
3
0.66
3.5
3
1.5
470
20
40
2.0
4.75
4
5
I
RUN/SS
V
RUN/SS
V
RUN/SSLO
I
SCL
I
SDLDO
I
SENSE
DF
MAX
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
LDO
EXT
V
EXTVCC
V
LDOHYS
f
NOM
f
LOW
f
HIGH
R
PLLIN
I
PLLFLTR
– 0.5
1.0
0.5
– 85
98
– 1.2
1.5
4.1
2
1.6
– 60
99.5
55
55
45
45
80
80
100
100
100
100
90
ns
ns
ns
ns
ns
ns
ns
Internal V
CC
Regulator
4.8
5.0
0.2
100
4.5
4.7
0.2
400
260
550
50
f
PLLIN
< f
OSC
f
PLLIN
> f
OSC
– 15
15
440
290
620
5.2
2.0
200
V
%
mV
V
V
kHz
kHz
kHz
kΩ
µA
µA
sn3729l6 3729l6fs
Oscillator and Phase-Locked Loop
3
LTC3729L-6
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 15V, V
RUN/SS
= 5V unless otherwise noted.
SYMBOL
R
RELPHS
CLKOUT
PARAMETER
Controller 2-Controller 1 Phase
Phase (Relative to Controller 1)
CONDITIONS
V
PHASMD
= 0V, Open
V
PHASMD
= 5V
V
PHASMD
= 0V
V
PHASMD
= Open
V
PHASMD
= 5V
4
0.2
I
PGOOD
= 2mA
V
PGOOD
= 5V
V
EAIN
with Respect to Set Output Voltage
V
EAIN
Ramping Negative
V
EAIN
Ramping Positive
–8
8
– 10
10
100
0.995
0V < V
CM
< 5V
Measured at V
OS
+ Input
46
1
55
80
1.005
0.1
0.3
±1
– 12
12
MIN
TYP
180
240
60
90
120
MAX
UNITS
Deg
Deg
Deg
Deg
Deg
V
V
V
µA
%
%
µs
V/V
dB
kΩ
ELECTRICAL CHARACTERISTICS
CLK
HIGH
CLK
LOW
V
PGL
I
PGOOD
V
PG
Clock High Output Voltage
Clock Low Output Voltage
PGOOD Voltage Low
PGOOD Leakage Current
PGOOD Trip Level, Either Controller
PGOOD Output
t
MASK
A
DA
CMRR
DA
R
IN
PGOOD Mask Timer
Gain
Common Mode Rejection Ratio
Input Resistance
Differential Amplifier Gain Block (Note 5)
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
according to the following formulas:
T
J
= T
A
+ (P
D
• 34°C/W)
Note 3:
The I.C. is tested in a feedback loop that servos V
ITH
to a specified
voltage and measures the resultant V
EAIN
.
Note 4:
Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency. See Applications Information.
Note 5:
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).
Note 6:
The LTC3729LEUH-6 is guaranteed to meet performance
specifications from 0°C to 70°C. Specifications over the – 40°C to 85°C
operating ambient temperature range are assured by design,
characterization and correlation with statistical process controls.
TYPICAL PERFOR A CE CHARACTERISTICS
Efficiency vs Output Current
(Figure 12)
100
100
V
EXTVCC
= 5V
80
V
IN
= 5V
90
EFFICIENCY (%)
EFFICIENCY (%)
60
V
IN
= 12V
V
IN
= 20V
80
40
V
OUT
= 3.3V
V
EXTVCC
= 5V
I
OUT
= 20A
T
A
= 25°C
0.1
1
10
OUTPUT CURRENT (A)
100
3729L-6 G01
70
EFFICIENCY (%)
V
IN
= 8V
20
0
4
U W
Efficiency vs Output Current
(Figure 12)
100
Efficiency vs Input Voltage
(Figure 12)
V
OUT
= 3.3V
V
EXTVCC
= 5V
I
OUT
= 20A
T
A
= 25°C
V
EXTVCC
= 0V
90
80
60
V
OUT
= 3.3V
T
A
= 25°C
1
10
OUTPUT CURRENT (A)
100
3729L-6 G02
50
70
5
10
V
IN
(V)
3729L-6 G03
15
20
sn3729l6 3729l6fs
LTC3729L-6
TYPICAL PERFOR A CE CHARACTERISTICS
Supply Current vs Input Voltage
and Mode
1000
ON
EXTV
CC
PIN OPEN
EXTV
CC
VOLTAGE DROP (mV)
800
SUPPLY CURRENT (µA)
T
A
= 25°C
600
200
250
INTV
CC
AND EXTV
CC
SWITCH VOLTAGE (V)
400
200
SHUTDOWN
0
0
5
20
15
10
INPUT VOLTAGE (V)
25
30
Internal 5V LDO Line Reg
5.1
5.0
75
INTV
CC
VOLTAGE (V)
4.9
V
SENSE
(mV)
4.8
4.7
4.6
4.5
4.4
0
5
I
LOAD
= 1mA
T
A
= 25°C
20
15
10
INPUT VOLTAGE (V)
25
30
V
SENSE
(mV)
Maximum Current Sense Threshold
vs V
RUN/SS
(Soft-Start)
80
V
SENSE(CM)
= 1.6V
T
A
= 25°C
60
V
SENSE
(mV)
V
SENSE
(mV)
72
V
SENSE
(mV)
40
20
0
0
1
2
3
V
RUN/SS
(V)
3729L-6 G10
4
U W
3729L-6 G04
3729L-6 G07
EXTV
CC
Voltage Drop
T
A
= 25°C
5.05
5.00
4.95
4.90
4.85
4.80
4.75
INTV
CC
and EXTV
CC
Switch
Voltage vs Temperature
INTV
CC
VOLTAGE
150
100
50
EXTV
CC
SWITCHOVER THRESHOLD
0
0
10
20
CURRENT (mA)
30
40
3729L-6 G05
4.70
– 50 – 25
50
25
75
0
TEMPERATURE (°C)
100
125
3729L-6 G06
Maximum Current Sense Threshold
vs Duty Factor
T
A
= 25°C
80
70
60
Maximum Current Sense Threshold
vs Percent of Nominal Output
Voltage (Foldback)
T
A
= 25°C
50
50
40
30
20
10
25
0
0
20
40
60
DUTY FACTOR (%)
80
100
3729L-6 G08
0
50
100
0
25
75
PERCENT ON NOMINAL OUTPUT VOLTAGE (%)
3729L-6 G09
Maximum Current Sense Threshold
vs Sense Common Mode Voltage
80
T
A
= 25°C
90
80
70
60
50
40
30
20
10
0
–10
–20
–30
Current Sense Threshold
vs I
TH
Voltage
T
A
= 25°C
76
68
64
60
5
6
0
1
3
4
2
COMMON MODE VOLTAGE (V)
5
3729L-6 G11
0
0.5
1
1.5
V
ITH
(V)
2
2.5
3729L-6 G12
sn3729l6 3729l6fs
5
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