LTC3730
3-Phase, 5-Bit Intel
Mobile VID, 600kHz,
Synchronous Buck Controller
FEATURES
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DESCRIPTIO
3-Phase Current Mode Controller with Onboard
MOSFET Drivers
±5%
Output Current Match Optimizes Thermal
Performance and Size of Inductors and MOSFETs
Operational Amplifier Accomodates Mode Switching
±1%
V
REF
Accuracy Over Temperature
Reduced Input and Output Capacitance
Reduced Power Supply Induced Noise
V
OUT
Programmable from 0.6V to 1.75V (IMVP III)
±10%
Power Good Output Indicator
250kHz to 600kHz Per Phase, PLL, Fixed Frequency
PWM, Stage Shedding
TM
or Burst Mode
®
Operation
OPTI-LOOP
®
Compensation Minimizes C
OUT
Adjustable Soft-Start Current Ramping
4V, V
IN
, Undervoltage RUN/SS Reset/Reattempt Circuit
Short-Circuit Shutdown Timer with Defeat Option
Overvoltage Soft Latch
Small 36-Lead Narrow (0.209”) SSOP Package
The LTC
®
3730 is a PolyPhase
®
synchronous step-down
switching regulator controller that drives all N-channel
external power MOSFET stages in a phase-lockable fixed
frequency architecture. The 3-phase controller drives its
output stages with 120° phase separation at frequencies of
up to 600kHz per phase to minimize the RMS losses in both
the input and output filter capacitors. The 3-phase tech-
nique effectively triples the fundamental frequency, im-
proving transient response while operating each controller
at an optimal frequency for efficiency and ease of thermal
design. Light load efficiency is optimized by using a choice
of output Stage Shedding or Burst Mode technology.
An internal operational amplifier provides mode selectable
output voltage programming in conjunction with the inter-
nal VID voltage control DAC.
Soft-start and a defeatable, timed short-circuit shutdown
protect the MOSFETs and the load. Current foldback
provides protection for the external MOSFETs under
short-circuit or overload conditions.
, LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode,
OPTI-LOOP and PolyPhase are registered trademarks of Linear Technology Corporation.
Stage Shedding is a trademark of Linear Technology Corporation. All other trademarks are
the property of their respective owners. Protected by U.S. Patents including 5481178,
5929620, 6177787, 6144194, 6100678, 5408150, 6580258, 6462525, 6304066, 5705919.
APPLICATIO S
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Tablet Computers
High Performance Notebook Computers
High Output Current DC/DC Power Supplies
TYPICAL APPLICATIO
V
CC
4.5V TO 7V
V
CC
10µF
LTC3730
BOOST1
BOOST2
BOOST3
0.1µF
SW3 SW2 SW1
TG1
SW1
BG1
SENSE1
+
SENSE1
–
TG2
SW2
BG2
PGND
SENSE2
+
SENSE2
–
TG3
SW3
BG3
SENSE3
+
SENSE3
–
V
IN
V
IN
1µH
0.003Ω
POWER GOOD INDICATOR
OPTIONAL SYNC IN
PGOOD
PLLIN
PLLFLTR
1µH
0.003Ω
5 VID BITS
680pF
VID0-VID4
I
TH
5k
0.1µF
100pF
RUN/SS
SGND
EAIN
AMPOUT
IN
–
IN
+
1µH
0.003Ω
Figure 1. High Current Triple Phase Step-Down Converter
3730fa
U
+
V
IN
5V TO 28V
22µF
35V
V
OUT
1.2V
50A
U
U
+
C
OUT
470µF
x4
2.5V
3730 F01
1
LTC3730
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
VID1
PLLIN
PLLFLTR
FCB
IN
+
IN
–
AMPOUT
EAIN
SGND
SENSE1
+
SENSE1
–
SENSE2
+
SENSE2
–
SENSE3
–
1
2
3
4
5
6
7
8
9
10
11
12
13
14
36 VID0
35 PGOOD
34 BOOST1
33 TG1
32 SW1
31 BOOST2
30 TG2
29 SW2
28 V
CC
27 BG1
26 PGND
25 BG2
24 BG3
23 SW3
22 TG3
21 BOOST3
20 VID4
19 VID3
Topside Driver Voltage (BOOST
N
) Range .. 38V to –0.3V
Switch Voltage (SW
N
) Range ........................ 32V to –5V
Boosted Driver Voltage (BOOST
N
– SW
N
) .... 7V to –0.3V
Peak Output Current <1ms (TG
N
, BG
N
) ..................... 5A
Supply Voltage (V
CC
), PGOOD
Pin Voltage Range ....................................... 7V to –0.3V
PLLIN, RUN/SS, PLLFLTR, FCB Voltages .. V
CC
to –0.3V
I
TH
Voltage Range ..................................... 2.4V to –0.3V
Operating Ambient Temperature Range ....... 0°C to 70°C
Junction Temperature (Notes 2, 7) ....................... 125°C
Storage Temperature Range ..................–65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
ORDER PART
NUMBER
LTC3730CG
SENSE3
+
15
RUN/SS 16
I
TH
17
VID2 18
G PACKAGE
36-LEAD PLASTIC SSOP
T
JMAX
= 125°C,
θ
JA
= 95°C/W
Order Options
Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking:
http://www.linear.com/leadfree/
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
SYMBOL
V
REGULATED
V
SENSEMAX
I
MATCH
V
LOADREG
PARAMETER
Regulated Voltage at IN
+
Maximum Current Sense Threshold
Maximum Current Threshold Match
Output Voltage Load Regulation
Main Control Loop
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= V
RUN/SS
= 5V unless otherwise noted.
CONDITIONS
(Note 3); VID Code = 11111, V
ITH
= 1.2V
●
MIN
0.596
0.594
65
62
–5
●
●
●
●
TYP
0.600
0.600
75
75
MAX
0.604
0.606
85
88
5
UNITS
V
V
mV
mV
%
%
%
%/V
mmho
MHz
V
µA
V
V
3730fa
V
EAIN
= 0.5V, V
ITH
Open,
V
SENSE1
–
,
V
SENSE2
–
,
V
SENSE3
– = 0.6V, 1.8V
Worst-Case Error at V
SENSE(MAX)
(Note 3)
Measured in Servo Loop,
∆I
TH
Voltage = 1.2V to 0.7V
Measured in Servo Loop,
∆I
TH
Voltage = 1.2V to 2V
V
CC
= 4.5V to 7V
I
TH
= 1.2V, Sink/Source 25µA (Note 3)
I
TH
= 1.2V, (g
m
• Z
L
, Z
L
= Series 1k-100kΩ-1nF)
●
0.1
–0.1
0.03
3.6
0.58
5
3
0.60
0.2
0.5
–0.5
6.6
0.62
0.7
V
REFLNREG
g
m
g
mOL
V
FCB
I
FCB
V
BINHIBIT
UVR
Output Voltage Line Regulation
Transconductance Amplifier g
m
Transconductance Amplifier GBW
Forced Continuous Threshold
FCB Bias Current
Burst Inhibit Threshold
Undervoltage RUN/SS Reset
V
FCB
= 0.65V
Measured at FCB pin
V
CC
Lowered Until the RUN/SS Pin is Pulled Low
V
CC
– 1.5 V
CC
– 0.7 V
CC
– 0.3
3.2
3.8
4.5
2
U
W
U
U
W W
W
LTC3730
ELECTRICAL CHARACTERISTICS
SYMBOL
I
Q
PARAMETER
Input DC Supply Current
Normal Mode
Shutdown
Soft-Start Charge Current
RUN/SS Pin ON Threshold
RUN/SS Pin Arming Threshold
RUN/SS Pin Latch-Off Threshold
RUN/SS Discharge Current
Shutdown Latch Disable Current
SENSE Pins Source Current
Maximum Duty Factor
Top Gate Rise Time
Top Gate Fall Time
Bottom Gate Rise Time
Bottom Gate 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
Maximum Low Level Input Voltage
Minimum High Level Input Voltage
VID0 to VID4 Internal Pull-Up Current
VID0 to VID4
PGOOD Voltage Output Low
PGOOD Output Leakage
PGOOD Trip Thesholds
V
AMPOUT
Ramping Negative
V
AMPOUT
Ramping Positive
Power Good Fault Report Delay
Nominal Frequency
Lowest Frequency
Highest Frequency
PLLIN Input Threshold
PLLIN Input Resistance
Phase Detector Output Current
Sinking Capability
Sourcing Capability
Controller 2-Controller 1 Phase
Controller 3-Controller 1 Phase
f
PLLIN
< f
OSC
f
PLLIN
> f
OSC
V
VID
= 0V
(Note 6)
I
PGOOD
= 2mA
V
PGOOD
= 5V
V
AMPOUT
with Respect to Set Output Voltage,
VID Code = 11111,
PGOOD Goes Low After V
UVDLY
Delay
After V
EAIN
is Forced Outside V
UV
Threshold
V
PLLFLTR
= 1.2V
V
PLLFLTR
= 0V
V
PLLFLTR
= 2.4V
360
190
600
–7
7
–10
11
100
400
225
680
1
50
20
20
120
240
●
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= V
RUN/SS
= 5V unless otherwise noted.
CONDITIONS
(Note 4)
V
CC
= 5V
V
RUN/SS
= 0V, VID0 to VID4 Open
V
RUN/SS
= 1.9V
V
RUN/SS
, Ramping Positive
V
RUN/SS
, Ramping Positive Until Short-Circuit
Latch-Off is Armed
V
RUN/SS
, Ramping Negative
Soft-Short Condition V
EAIN
= 0.375V, V
RUN/SS
= 4.5V
V
EAIN
= 0.375V, V
RUN/SS
= 4.5V
SENSE1
+
, SENSE1
–
, SENSE2
+
, SENSE2
–
,
SENSE3
+
, SENSE3
–
All Equal 1.2V; Current at Each Pin
In Dropout, V
SENSEMAX
≤
30mV
C
LOAD
= 3300pF
C
LOAD
= 3300pF
C
LOAD
= 3300pF
C
LOAD
= 3300pF
All Controllers, C
LOAD
= 3300pF Each Driver
All Controllers, C
LOAD
= 3300pF Each Driver
Tested with a Square Wave (Note 5)
95
–5
–0.8
1
MIN
TYP
2.3
20
–1.5
1.5
3.8
3.2
–1.5
1.5
13
98.5
30
40
30
20
50
60
110
0.4
2
3
– 0.25
0.1
0.25
0.3
±1
–13
13
150
440
260
750
90
90
90
90
5
20
MAX
3.5
50
–2.5
1.9
4.5
UNITS
mA
µA
µA
V
V
V
µA
µA
µA
%
ns
ns
ns
ns
ns
ns
ns
V
V
µA
%
V
µA
%
%
µs
kHz
kHz
kHz
V
kΩ
µA
µA
Deg
Deg
3730fa
I
RUN/SS
V
RUN/SS
V
RUN/SSARM
V
RUN/SSLO
I
SCL
I
SDLHO
I
SENSE
DF
MAX
TG t
R,
t
F
BG t
R,
t
F
TG/BG t
1D
BG/TG t
2D
t
ON(MIN)
VID
IL
VID
IH
VID
PULLUP
ATTEN
ERR
V
PGL
I
PGOOD
V
PGTHNEG
V
PGTHPOS
V
UVDLY
f
NOM
f
LOW
f
HIGH
R
PLLTH
R
PLL IN
I
PLL LPF
VID Parameters
Power Good Output Indication
Oscillator and Phase-Locked Loop
R
RELPHS
3
LTC3730
ELECTRICAL CHARACTERISTICS
SYMBOL
I
B
V
OS
CM
CMRR
I
CL
A
VOL
GBP
SR
V
O(MAX)
T
SHDN
PARAMETER
Input Bias Current
Input Offset Voltage Magnitude
Common Mode Input Voltage Range
Common Mode Rejection Ratio
Output Source Current
Open-Loop DC Gain
Gain Bandwidth Product
Slew Rate
Maximum High Output Voltage
Temperature Shutdown
I
OUT
= 1mA
I
OUT
= 1mA
R
L
= 2k
I
OUT
= 1mA
Temperature Rising
I
OUT
= 1mA
IN
+
= IN
–
= 1.2V, I
OUT
= 1mA
0
46
10
70
35
30
2
5
V
CC
– 1.2 V
CC
– 0.9
130
165
Operational Amplifier
15
0.8
200
5
V
CC
– 1.4
nA
mV
V
dB
mA
V/µV
MHz
V/µs
V
°C
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= V
RUN/SS
= 5V unless otherwise noted.
CONDITIONS
MIN
TYP
MAX
UNITS
Overtemperature Shutdown
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired. A maximum current of 200µA is allowed to
pull up the RUN/SS pin to prevent overcurrent shutdown.
Note 2:
T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
according to the following formula:
LTC3730CG: T
J
= T
A
+ (P
D
×
95°C/W)
Note 3:
The IC is tested in a feedback loop that includes the operational
amplifier in a unity-gain configuration loaded with 100µA to ground driving
the VID DAC into the error amplifier and servoing the resultant voltage to
the midrange point for the error amplifier (V
ITH
= 1.2V).
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 an inductor peak-
to-peak ripple current of
≥
40% of I
MAX
(see minimum on-time
considerations in the Applications Information Section).
Note 6:
The ATTEN
ERR
specification is in addition to the output voltage
accuracy specified at VID Code = 11111.
Note 7:
This IC includes overtemperature protection that is intended to protect
the device during momentary overload conditions. Junction temperature will
exceed 125°C when overtemperature protection is active. Continuous operation
above the specified maximum operating junction temperature may impair
device reliability.
3730fa
4
LTC3730
TYPICAL PERFOR A CE CHARACTERISTICS
Efficiency vs I
OUT
(Figure 14)
100
90 V
FCB
= OPEN
80 V
FCB
= 5V
V
FCB
= 0V
70
60
50
40
30
20
10
0
0.1
1
10
V
IN
= 8V
V
OUT
= 1.5V
100
3730 G01
EFFICIENCY (%)
EFFICIENCY (%)
80
75
70
65
60
55
50
0
5
I
OUT
= 45A
EFFICIENCY (%)
LOAD CURRENT (A)
Reference Voltage vs
Temperature
610
6.0
605
MAXIMUM I
SENSE
THRESHOLD (mV)
ERROR AMPLIFIER g
m
(mmho)
REFERENCE VOLTAGE (mV)
600
595
590
–50 –30 –10
10 30 50 70
TEMPERATURE (°C)
Oscillator Frequency vs
Temperature
700
OSCILLATOR FREQUENCY (kHz)
600
500
400
V
PLLFLTR
= 1.2V
300
200
100
0
–45 –30 –15
0 15 30 45 60
TEMPERATURE (°C)
75
90
V
PLLFLTR
= 0V
V
PLLFLTR
= 2.4V
700
500
UNDER VOLTAGE RESET (V)
V
PLLFLTR
= 5V
FREQUENCY (kHz)
U W
90
3730
G04
3730
G07
Efficiency vs V
IN
(Figure 14)
100
95
90
85
I
OUT
= 15A
V
OUT
= 1.5V
f = 250kHz
100
Efficiency vs Frequency (Figure 14)
I
LOAD
= 20A
V
OUT
= 1.5V
95
V
IN
= 5V
90
V
IN
= 12V
85
V
IN
= 20V
80
V
IN
= 8V
10
15
V
IN
(V)
20
25
3730 G02
75
200
300
400
FREQUENCY (kHz)
500
600
3730 G03
Error Amplifier gm vs
Temperature
85
Maximum I
SENSE
Threshold vs
Temperature
5.5
80
V
O
= 1.75V
75
V
O
= 0.6V
70
5.0
4.5
110
4.0
–45 –30 –15
0 15 30 45 60
TEMPERATURE (°C)
75
90
65
–45 –30 –15
0 15 30 45 60
TEMPERATURE (°C)
75
90
3730
G05
3730
G06
Oscillator Frequency vs V
PLLFLTR
5
Undervoltage Reset Voltage vs
Temperature
600
4
3
400
2
300
1
200
0
0.5
1
1.5
2
PLLFLTR PIN VOLTAGE (V)
2.5
3730
G08
0
–45 –30 –15
0 15 30 45 60
TEMPERATURE (°C)
75
90
3730
G09
3730fa
5
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