LTC3773
Triple Output Synchronous
3-Phase DC/DC Controller with
Up/Down Tracking
FEATURES
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DESCRIPTION
The LTC
®
3773 is a high performance, 3-phase, triple output
synchronous step-down switching regulator controller
with output voltage power up/down tracking capability.
The controller allows for sequential, coincident or ratio-
metric tracking.
This 3-phase controller drives its output stages with 120°
phase separation at frequencies of up to 700kHz per phase
minimizing the RMS input current. Light load efficiency can
be maximized by using selectable Burst Mode operation.
The 0.6V precision reference supports output voltages
from 0.6V to 5V.
Fault protection features include output overvoltage, input
undervoltage lockout plus current foldback under short-
circuit or overload conditions.
, LT, LTC, LTM, Burst Mode and OPTI-LOOP are registered trademarks of
Linear Technology Corporation. All other trademarks are the property of their respective
owners. Protected by U.S. Patents including 5408150, 5481178, 5705919, 5929620,
6144194, 6177787, 6304066, 6498466, 6580258, 6611131.
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Current Mode Controller with Onboard
MOSFET Drivers
Programmable Power Up/Down Tracking
Wide V
IN
Range: 3.3V to 36V (V
CC
= 5V)
±1% 0.6V V
FB
Accuracy Over Temperature
Power Good Output Voltage Monitor
Phase-Lockable or Adjustable Frequency:
160kHz to 700kHz
OPTI-LOOP
®
Compensation Minimizes C
OUT
Current Foldback and Overvoltage Protection
Selectable Continuous, Discontinuous or
Burst Mode
®
Operation at Light Load
Programmable Phase Operation
Available in 5mm x 7mm QFN and 36-Lead
SSOP Packages
APPLICATIONS
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Servers, Telecom, Industrial Power Supplies
General Purpose Multiple Rail DC/DC
FPGA and DSP Requirements
TYPICAL APPLICATION
High Efficiency, 3-Phase, Triple Synchronous DC/DC Step-Down Controller
10k
PGOOD
SW1, 2, 3
PGOOD V
CC
POWER UP/SHUTDOWN
0.01μF
SDB1, 2, 3
TRACK1, 2, 3
LTC3773
BOOST1, 2, 3
V
DR
TG2
SW2
BG2
SENSE2+
SENSE2–
V
FB2
TG3
SW3
BG3
SENSE1+
SENSE1–
31.6k
10k
V
FB1
I
TH1, 2, 3
PLLFLTR
SGND
PGND
SENSE3+
SENSE3–
V
FB3
3773 F01
V
CC
4.5V TO 6V
0.1μF
10μF
V
IN
4.5V TO 22V
1.5μH
V
OUT2
0.003Ω 1.8V/15A
C
IN
+
C
OUT2
20k
V
OUT1
2.5V/15A 0.003Ω
C
OUT1
V
IN
2.2μH
TG1
SW1
BG1
V
IN
1.2μH
V
OUT3
0.003Ω 1.2V/15A
C
OUT3
10k
20k
20k
3773fb
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LTC3773
ABSOLUTE MAXIMUM RATINGS
(Note 1)
Topside Driver Voltage (BOOSTn) .............. 42V to –0.3V
Switch Voltage (SWn) ................................... 36V to –1V
Boosted Driver Voltage (BOOSTn – SWn) .... 7V to –0.3V
Supply Voltages (V
CC
, V
DR
).......................... 7V to –0.3V
PGOOD, PHASEMD, PLLFLTR, PLLIN/FC, SDBn,
TRACKn, V
FB
n ...............................(V
CC
+ 0.3V) to –0.3V
SENSE
+
n, SENSE
–
n ........................ (1.1 • V
CC
) to –0.3V
I
THn
Voltage............................................... 2.7V to –0.3V
Extended Commercial Operating
Temperature Range (Note 2)................–40°C to 85°C
Junction Temperature (Note 2) ............................. 125°C
Storage Temperature Range...................–65°C to 125°C
Lead Temperature (Soldering, 10 sec)
G Package ......................................................... 300°C
Peak Body Temperature UHF Package................... 240°C
PIN CONFIGURATIONS
SDB3
SDB2
SENSE1
–
SDB
TRACK1
V
FB1
I
TH1
SGND
I
TH2
I
TH3
2
3
4
5
6
7
8
9
35 PGOOD
34 BOOST1
33 TG1
32 SW1
31 SW2
30 TG2
29 BOOST2
28 BOOST3
27 TG3
26 SW3
25 BG1
24 BG2
23 V
DR
22 PGND
21 BG3
20 PLLIN/FC
19 PLLFLTR
G PACKAGE
36-LEAD PLASTIC SSOP
TRACK1 1
V
FB1
2
I
TH1
3
SGND 4
I
TH2
5
I
TH3
6
V
FB2
7
V
FB3
8
TRACK2 9
TRACK3 10
SENSE2 11
SENSE2
+
12
13 14 15 16 17 18 19
V
CC
SENSE3
+
SENSE3
–
PLLFLTR
PLLIN/FC
CLKOUT
BG3
–
38 37 36 35 34 33 32
31 BOOST1
30 TG1
29 SW1
28 SW2
27 TG2
39
26 BOOST2
25 BOOST3
24 TG3
23 SW3
22 BG1
21 BG2
20 V
DR
V
FB2
10
V
FB3
11
TRACK2 12
TRACK3 13
SENSE2
–
14
SENSE2
+
15
SENSE3
–
16
SENSE3+ 17
V
CC
18
T
JMAX
= 125°C,
θ
JA
= 95°C/W
UHF PACKAGE
38-LEAD (5mm
×
7mm) PLASTIC QFN
EXPOSED PAD IS PGND (PIN 39),
MUST BE SOLDERED TO PCB
T
JMAX
= 125°C,
θ
JA
= 34°C/W
ORDERING INFORMATION
LEAD FREE FINISH
LTC3773EG#PBF
LTC3773EUHF#PBF
TAPE AND REEL
LTC3773EG#TRPBF
LTC3773EUHF#TRPBF
3773E
PART MARKING
PACKAGE DESCRIPTION
36-Lead Plastic SSOP
38-Lead (5mm x 7mm) Plastic QFN
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
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/
SDB1
1
36 PHASEMD
PGOOD
SENSE1
+
PHASEMD
TOP VIEW
TOP VIEW
SENSE1
–
SENSE1
+
3773fb
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LTC3773
ELECTRICAL CHARACTERISTICS
SYMBOL
Main Control Loop
V
FB
I
VFB
V
SENSEMAX
V
FBLOADREG
Feedback Voltage
Feedback Pin Input Current
Maximum Current Sense Threshold
Feedback Voltage Load Regulation
V
ITH
= 1.2V, 0°C ≤ T ≤ 85°C (Note 4)
●
(Note 3) The
●
denotes the specifications which apply over the full
operating temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= V
DR
= V
BOOST
= V
SDB
= 5V, unless otherwise noted.
PARAMETER
CONDITIONS
MIN
0.594
0.591
65
60
TYP
0.600
0.600
–15
●
MAX
0.606
0.609
–100
85
90
0.5
–0.5
3.2
UNITS
V
V
nA
mV
mV
%
%
%/V
mmho
MHz
dB
0 ≤ V
FB
≤ 1V
V
FB
= 0.55V, V
TRACK
= 1V, V
SENSE–
= 2.5V
Measured in Servo Loop (Note 4)
Δ
ITH
Voltage = 1.2V to 0.7V
Δ
ITH
Voltage = 1.2V to 2V
V
CC
= 4.5V to 6V
V
ITH
= 1.2V, Sink/Source 25μA (Note 4)
V
ITH
= 1.2V (Note 5)
V
ITH
= 0.8V to 1.6V
V
CC
Ramping Positive
●
●
●
75
75
0.15
–0.2
0.01
●
●
V
FBLNREG
g
m
f
u
A
ERR
V
UVR
V
CC
I
VCC
Feedback Voltage Line Regulation
Transconductance Amplifier g
m
Transconductance Amplifier GBW
Transconductance Amplifier DC Gain
V
CC
Undervoltage Reset
Undervoltage Hysteresis
V
CC
Supply Voltage
V
CC
Supply Current
Normal Mode
Shutdown
V
DR
Supply Current
Normal Mode
Shutdown
V
BOOST
Supply Current
Normal Mode
Shutdown
SDB Source Current
SDB1, SDB2, SDB3 Source Content
SDB Power Up Threshold
SDB1 Pin CH1 ON Threshold
SDB2 Pin CH2 ON Threshold
SDB3 Pin CH3 ON Threshold
Channel On Threshold Hysteresis
SENSE Pins Source Current
Maximum Duty Factor
TG Driver Pull-Up On-Resistance
TG Driver Pull-Down On-Resistance
BG Driver Pull-Up On-Resistance
BG Driver Pull-Down On-Resistance
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
TRACK Pin Pull-Up Current
V
FB
Voltage During Tracking
2.3
50
3.7
4.5
2.7
3
56
4.1
0.16
5
2.8
20
5
1
1
1
–1.5
–0.5
4.4
6
4
30
V
V
V
mA
μA
mA
μA
mA
μA
μA
μA
V
CC
= 5V
V
SDB
= 0V
V
DR
= 5V (Note 6)
V
SDB
= 0V
V
BOOST
= 5V, V
SW
= 0V (Note 6)
V
SDB
= 0V
I
VDR
I
BOOST
I
SDB
V
SDB
Ramping Positive
●
●
●
●
0.4
1.14
1.71
2.3
1.2
1.8
2.4
–10
–13
1.26
1.89
2.5
–20
V
V
V
V
%
μA
%
Ω
Ω
Ω
Ω
ns
ns
ns
μA
I
SENSE
DF
MAX
TG R
UP
TG R
DOWN
BG R
UP
BG R
DOWN
TG/BG t
1D
BG/TG t
2D
t
ON(MIN)
Tracking
I
TRACK
V
FBTRACK
V
SENSE+
, V
SENSE–
= 1.2V, Current at Each Pin
PLLFLTR Floats, In Dropout
TG High, I
OUT
= 100mA (Note 7)
TG Low, I
OUT
= 100mA (Note 7)
BG High, I
OUT
= 100mA (Note 7)
BG Low, I
OUT
= 100mA (Note 7)
All Controllers
All Controllers
Tested with a Square Wave (Note 8)
V
SDB
= 5V, V
TRACK
= 0V
V
TRACK
= 0.2V, V
ITH
= 1.2V (Note 4)
V
TRACK
= 0.4V, V
ITH
= 1.2V (Note 4)
180
380
97
98.5
2.2
1.8
2.4
0.9
50
50
130
–1
200
400
220
420
mV
mV
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LTC3773
ELECTRICAL CHARACTERISTICS
SYMBOL
V
PGL
I
PGOOD
V
PGTHNEG
V
PGTHPOS
V
PGDLY
f
NOM
f
LOW
f
HIGH
f
PLLLOW
f
PLLHIGH
PARAMETER
PGOOD Voltage Output Low
PGOOD Output Leakage
PGOOD Trip Thresholds
V
FB
Ramping Negative
V
FB
Ramping Positive
PGOOD Delay
Nominal Frequency
Low Frequency
High Frequency
PLLIN Minimum Input Frequency
PLLIN Maximum Input Frequency
PLLIN/FC, PHASEMD, PLLFLTR
Logic Input
Low Level Input Voltage
Floating Voltage
High Level Input Voltage
PLLIN Synchronization Input Threshold
Phase Detector Output Current
Sinking Capability
Sourcing Capability
Controller 2 - Controller 1 Phase
Controller 3 - Controller 1 Phase
Controller 2 - Controller 1 Phase
Controller 3 - Controller 1 Phase
CLKOUT
Controller 1 TG to CLKOUT Phase
V
PLLFLTR
= 1.5V
f
PLLIN
< f
OSC
f
PLLIN
> f
OSC
PHASEMD Floats or V
PHASEMD
= 0V
V
PHASEMD
= 5V
PHASEMD Floats
V
PHASEMD
= 0V
V
PHASEMD
= 5V
540
V
PLLFLTR
Open
V
PLLFLTR
= 0V
V
PLLFLTR
= 5V
Power Good Output Indication
I
PGOOD
= 2mA
V
PGOOD
= 5V
V
FB
with Respect to 0.6V Reference
PGOOD Goes Low After V
PGDLY
Delay
–7
7
100
360
190
510
–10
10
150
400
220
560
160
700
440
250
630
200
0.1
0.3
1
–13
13
V
μA
%
%
μs
kHz
kHz
kHz
kHz
kHz
(Note 3) The
●
denotes the specifications which apply over the full
operating temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= V
DR
= V
BOOST
= V
SDB
= 5V, unless otherwise noted.
CONDITIONS
MIN
TYP
MAX
UNITS
Oscillator and Phase-Locked Loop
V
LO
V
FLOAT
V
HI
V
PLLIN
I
PLLFLTR
1.0
1.6
3.0
1
25
–25
120
240
90
270
0
60
180
V
V
V
V
μA
μA
Deg
Deg
Deg
Deg
Deg
Deg
Deg
P
RELPHS
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 LTC3773 is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls. T
J
is calculated from the ambient
temperature T
A
and power dissipation P
D
according to the following
formula.
LTC3773EG: T
J
= T
A
+ (P
D
x 95°C/W)
LTC3773EUHF: T
J
= T
A
+ (P
D
x 34°C/W)
Note 3:
All currents into device pins are positive; all currents out of device
pins are negative. All voltages are referenced to ground unless otherwise
specified.
Note 4:
The IC is tested in a feedback loop that adjusts V
FB
to achieve a
specified error amplifier output voltage (V
ITH
).
Note 5:
Guaranteed by design, not subject to test.
Note 6:
Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency. See Applications Information.
Note 7:
R
DS(ON)
limit is guaranteed by design and/or correlation to static
test.
Note 8:
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).
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LTC3773
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency vs Load Current,
Shutdown CH2 and CH3
100
90
CHANNEL 1 EFFICIENCY (%)
CHANNEL 1 EFFICIENCY (%)
80
70
60
50
40
30
20
10
0
0.001
0.01
0.1
1
CONTINUOUS
MODE
DISCONTINUOUS
MODE
Burst Mode
OPERATION
EFFICIENCY
POWER LOSS
10
100
1000
POWER LOSS (mW)
10000
100
90
80
70
60
50
40
30
20
10
0
0.001
0.01
0.1
1
CONTINUOUS 100
MODE
DISCONTINUOUS
MODE
Burst Mode
OPERATION
EFFICIENCY
POWER LOSS
10
10
1000
POWER LOSS (mW)
Efficiency vs Load Current,
Power-Up CH2 and CH3
10000
10
1
1
0.1
100
0.1
100
CHANNEL 1 LOAD CURRENT (A)
V
IN
= 12V, V
CC
= 5V, V
OUT1
= 2.5V
f
SW
= 220kHz
3773 G01
CHANNEL 1 LOAD CURRENT (A)
V
IN
= 12V, V
CC
= 5V, V
OUT1
= 2.5V
V
OUT2
= 1.8V (NO LOAD), V
OUT3
= 1.2V (NO LOAD)
3773 G02
f
SW
= 220kHz
Efficiency vs V
IN
Shutdown CH2 and CH3
100
V
CC
= 5V, V
OUT1
= 2.5V, I
OUT1
= 5A
SHUTDOWN CH2 AND CH3
4.0
5
0
POWER LOSS (W)
–5
–10
–15
–20
–25
Load Regulation
V
IN
= 12V, V
CC
= 5V, V
OUT
= 2.5V
0.2
0.0
NORMALIZED
ΔV
OUT
(%)
–0.2
–0.4
–0.6
CONTINUOUS MODE
DISCONTINUOUS MODE
Burst Mode OPERATION
0
5
15
10
LOAD CURRENT (A)
–0.8
–1.0
20
3773 G04
CHANNEL 1 EFFICIENCY (%)
95
90 PLLFLTR = 5V
f
SW
= 560kHz
PLLFLTR FLOATS
f
SW
= 400kHz
85
PLLFLTR = 0V
f
SW
= 220kHz
80
EFFICIENCY
POWER LOSS
0
5
10
15
V
IN
(V)
20
3.2
2.4
1.6
0.8
75
0.0
25
3773 G03
Line Regulation
2.5
2.0
1.5
1.0
ΔV
OUT
(mV)
0.5
0
–0.5
–1.0
–1.5
–2.0
–2.5
0
5
10
15
V
IN
(V)
20
V
CC
= 5V, V
OUT
= 2.5V, I
OUT
= 5A
1.0
0.8
MAXIMUM LOAD CURRENT (A)
0.6
0.4
0.2
0
–0.2
–0.4
–0.6
–0.8
25
3773 G05
ΔV
OUT
(mV)
Current Limit vs V
IN
25
20
15
R
SENSE
= 5mΩ
10
5
0
V
CC
= 5V, V
OUT
= 2.5V, f
SW
= 220kHz
0
5
10
15
V
IN
(V)
20
25
3773 G06
R
SENSE
= 3mΩ
NOMALIZED
ΔV
OUT
(mV/V)
–1.0
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