LTC3802
Dual 550kHz Synchronous
2-Phase DC/DC Controller with
Programmable Up/Down Tracking
FEATURES
s
s
DESCRIPTIO
s
s
s
s
s
s
s
s
s
s
Wide V
IN
Range: 3V to 30V Operation with Line
Feedforward Compensation
Leading Edge Modulation Architecture for
Extremely Low Duty Cycle Operation
Phase-Lockable Fixed Frequency: 330kHz to 750kHz
Two 180° Out-of-Phase Controllers
Fast Programmable Power-Up/-Down Tracking
Programmable Current Limit Without External
Current Sense Resistor
Optional Burst Mode
®
Operation at Light Load
±1%
0.6V Voltage Reference
External N-Channel MOSFET Architecture
Low Shutdown Current: <100µA
Overvoltage Protection and PGOOD Flag
Small 28-Lead SSOP and 32-Lead QFN Packages
The LTC
®
3802 is a dual switching regulator controller
optimized for high efficiency step-down conversion from
input voltages between 3V to 30V. The controller uses a
leading edge modulation scheme to allow extremely low
duty cycle operation. The constant frequency voltage mode
controller allows a phase-lockable frequency between
330kHz and 750kHz. Power loss and noise due to the ESR
of the input capacitors are minimized by operating the two
controller output stages 180° out of phase. The synchro-
nous buck architecture automatically shifts to Burst Mode
operation as the output load decreases, ensuring maxi-
mum efficiency over a wide range of load currents.
The LTC3802 features an onboard, trimmed 0.6V refer-
ence and provides better than 1% regulation at the con-
verter outputs. A separate output sense provides real time
overvoltage protection and PGOOD sensing. An FBT pin
programs the power-up/-down tracking between the two
channels to meet various sequencing requirements. A
RUN/SS pin provides soft-start and externally program-
mable current limit protection functions.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
U.S. Patent Nos 5481178, 5846544, 6304066, 6580258, 5055767, 6307356
APPLICATIO S
s
s
s
s
Notebook and Palmtop Computers
Portable Instruments
Battery-Operated Digital Devices
DC Power Distribution Systems
TYPICAL APPLICATIO
V
IN
5V TO 22V
+
56µF
25V
×2
4.7µF
25V
×8
1µH
5V
CMDSH-3
Si7860DP
×2
0.1µF
+
CMDSH-3
TG1
PV
CC
TG2
BOOST2
10µF
Si7860DP
×2
1µH
0.1µF
Si7440DP
×2
47k
B340B
330µF
4V
×3
V
OUT2
2.5V
15A
V
OUT1
3.3V
15A
10k
10k
B340B
+
330µF
4V
×3
560pF
Si7440DP
×2
47k
SW2
BOOST1
BG2
SW1
PLLIN
BG1
PLLLPF
PGND
LTC3802
I
MAX2
I
MAX1
FBT
CMPIN1
COMP1
FB1
SGND
FCB
RUN/SS
0.1µF
CMPIN2
V
CC
COMP2
FB2
PHASEMD
V
INFF
PGOOD
10k
5V
2.21k
2.21k
1500pF
390Ω
15k
330pF
2200pF
+
0.1µF
330pF
3802 TA01
V
IN
0.47µF
U
+
10k
10k
3.16k
5V
10Ω
10µF
2200pF
15k
560pF
1500pF
390Ω
3.16k
U
U
3802f
1
LTC3802
ABSOLUTE
AXI U RATI GS
Supply Voltage
V
CC
, PV
CC
............................................................. 7V
BOOSTn .............................................................. 37V
BOOSTn – SWn .................................................... 7V
SWn ........................................................ –1V to 30V
Input Voltage
V
INFF
.................................................................... 30V
FBn, CMPINn, FBT, PLLIN, FCB,
RUN/SS, PGOOD, PLLLPF, PHASEMD,
EXTREF, I
MAX
n
.......................... –0.3V to V
CC
+ 0.3V
PACKAGE/ORDER I FOR ATIO
TOP VIEW
PV
CC
BG1
BOOST1
TG1
SW1
PGND
I
MAX1
FBT
CMPIN1
1
2
3
4
5
6
7
8
9
28 BG2
27 BOOST2
26 TG2
25 SW2
24 PLLIN
23 PLLLPF
22 I
MAX2
21 CMPIN2
20 V
CC
19 COMP2
18 FB2
17 PHASEMD
16 V
INFF
15 PGOOD
BOOST1
BOOST2
PV
CC
LTC3802EGN
SW1 1
PGND 2
PGND 3
I
MAX1
4
FBT 5
CMPIN1 6
COMP1 7
FB1 8
SW2
BG1
BG2
TG1
TG2
ORDER PART
NUMBER
COMP1 10
FB1 11
SGND 12
FCB 13
RUN/SS 14
EXTREF
RUN/SS
SGND
PGOOD
V
INFF
FCB
PHASEMD
GN PACKAGE
28-LEAD PLASTIC SSOP
UH PACKAGE
32-LEAD (5mm
×
5mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 34°C/W
EXPOSED PAD (PIN 33) IS GND
MUST BE SOLDERED TO PCB
T
JMAX
= 125°C,
θ
JA
= 110°C/W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
The
q
denotes the specifications which apply over the full operating
temperature range. (Note 3) V
CC
= PV
CC
= BOOST = 5V, unless otherwise specified.
SYMBOL
V
CC
PV
CC
BV
CC
V
UVLO
I
VCC
PARAMETER
V
CC
Supply Voltage
PV
CC
Supply Voltage
BOOST Pin Voltage
Positive Undervoltage Lockout
V
CC
Supply Current
(Note 4)
V
BOOST
– V
SW
(Note 4)
Measured at V
CC
Measured at V
INFF
V
FB
= V
COMP
V
RUN/SS
= 0V, PLLIN Floating
q
q
ELECTRICAL CHARACTERISTICS
CONDITIONS
q
q
q
FB2
2
U
U
W
W W
U
W
(Note 1)
Extended Commercial
Operating Temperature Range (Note 2) .. –40°C to 85°C
Storage Temperature Range
LTC3802EGN ................................... – 65°C to 150°C
LTC3802EUH ................................... – 65°C to 125°C
Lead Temperature (Soldering, 10 sec)
LTC3802EGN Only ........................................... 300°C
TOP VIEW
ORDER PART
NUMBER
LTC3802EUH
24 PGND
23 PGND
22 PLLIN
32 31 30 29 28 27 26 25
33
21 PLLLPF
20 I
MAX2
19 CMPIN2
18 V
CC
17 COMP2
UH PART
MARKING
3802
9 10 11 12 13 14 15 16
MIN
3
TYP
5
5
5
MAX
6
6
6
2.8
2.8
9
150
UNITS
V
V
V
V
V
mA
µA
3802f
2.2
2.2
2.5
2.5
6.5
100
LTC3802
The
q
denotes the specifications which apply over the full operating
temperature range. (Note 3) V
CC
= PV
CC
= BOOST = 5V, unless otherwise specified.
SYMBOL
I
PVCC
I
BOOST
PARAMETER
PV
CC
Supply Current
BOOST Pin Current
CONDITIONS
V
FB
= V
CMPIN
= 0V, No Load
V
RUN/SS
= 0V (Notes 5, 6)
V
FB
= V
CMPIN
= 0V, No Load
V
RUN/SS
= 0V (Notes 5, 6)
V
EXTREF
= 5V, 0°C
≤
T
≤
70°C
V
EXTREF
= 5V
V
CC
= 4.5V to 6V
(Note 7)
No Load, V
EXTREF
= V
RUN/SS
= V
CC
f = 100kHz (Note 7)
V
RUN/SS
= V
CC
V
FB
= 0V to 1V
V
CMPIN
= 0V to 1V
V
FBT
= 0V to 1V
V
EXTREF
= 0V to 5V
V
VINFF
= 5V to 30V
With Respect to 0.6V
With Respect to 0.6V
With Respect to V
FB
q
q
q
q
q
q
q
q
ELECTRICAL CHARACTERISTICS
MIN
TYP
2
1
1
1
MAX
10
10
0.606
0.609
±0.2
UNITS
mA
µA
mA
µA
V
V
%/V
%
dB
MHz
mA
Switcher Control Loop
V
FB
∆V
FB
∆V
OUT
A
ERR
GBW
I
COMP
I
FB
I
CMPIN
I
FBT
I
EXTREF
V
EXTREF
A
LFF
R
VINFF
V
PGOOD
V
OVP
V
BURRS
V
SAW
I
IMAX
I
LIM(TH)
Feedback Voltage
Feedback Voltage V
CC
Line Regulation
Output Voltage Load Regulation
Error AMP DC Gain
Error AMP Gain Bandwidth Product
Error AMP Output Sink/Source Current
Voltage Feedback Input Current
Comparators Input Current
FBT Input Current
EXTREF Input Current
External Reference Not to Affect V
FB
∆
Drop in Duty Cycle/∆ V
INFF
V
INFF
Input Resistance
Positive Power Good Threshold
Negative Power Good Threshold
Overvoltage Threshold
(V
CMPIN
– V
FB
) to Reset
Burst Mode Operation
SAW Before Line Compensation
I
MAX
Source Current
I
LIM
Comparator Offset
V
IMAX
/I
LIM
Threshold
Hard I
LIM
/I
LIM
Threshold
RUN/SS Source Current
RUN/SS Sink/Source Current Ratio
RUN/SS Sink Current, I
LIM
RUN/SS Sink Current, Hard I
LIM
RUN/SS Shutdown Threshold
PHASEMD Pull-Up Current
PHASEMD Pull-Down Current
PLLIN, FCB High Level Input Voltage
PLLIN, FCB Low Level Input Voltage
V
PGOOD
Leakage Current
V
PGOOD
Output Low Voltage
V
PGOOD
Falling Edge Delay
V
PGOOD
Rising Edge Delay
Power Good
I
PGOOD
= 1mA
(Note 8)
(Note 8)
q
q
q
0.594
0.591
0.600
0.600
±0.01
0.1
70
80
10
±12
±1
±1
±1
±1
µA
µA
µA
µA
V
%/V
MΩ
1
2.3
1
5
–5
3
10
–10
5
15
–12
1.2
15
–15
9
%
%
%
mV
mV
V
V
IMAX
= 1V
q
q
–9.0
–8.5
–15
–10
–10
0
5
1.5
–7
2
100
0.8
–7
2
–11.0
–11.5
15
µA
µA
mV
V/V
V/V
µA
µA/µA
µA
mA
V
µA
µA
V
V
CMPIN
= 0V
V
CMPIN
= V
FBT
= 0.6V, V
PHASEMD
= V
CC
V
CMPIN
= V
FBT
= 0.6V, V
PHASEMD
= 0V
V
CMPIN
= V
FBT
= 0.6V
V
CMPIN
= V
FBT
= 0V
RUN/SS↑
V
PHASEMD
= 0V
V
PHASEMD
= 5V
q
q
I
SS
–5
1.5
q
q
–9
2.5
1
0.4
1.2
V
SHDN
I
PHASEMD
V
IH
V
IL
I
PGOOD
V
OLPG
t
PGOOD
LOGIC and PGOOD
2.4
0.8
±1
0.1
100
150
10
0.3
V
µA
V
µs
µs
3802f
3
LTC3802
The
q
denotes the specifications which apply over the full operating
temperature range. (Note 3) V
CC
= PV
CC
= BOOST = 5V, unless otherwise specified.
SYMBOL
f
OSC
PARAMETER
Oscillator Frequency
CONDITIONS
PLLIN Open or V
PLLIN
= 0V
V
PLLLPF
= 1.2V
V
PLLLPF
= 0V
V
PLLLPF
= 2.4V
MIN
490
250
650
TYP
550
550
330
750
5
f
PLLIN
> f
OSC
f
PLLIN
< f
OSC
PHASEMD Floats
V
PHASEMD
= 5V
PHASEMD Floats
V
PHASEMD
= 5V
q
q
ELECTRICAL CHARACTERISTICS
MAX
610
400
850
UNITS
kHz
kHz
kHz
kHz
µA
µA
µA
Deg
Deg
Deg
Deg
V
V
V
%
%
ns
ns
Switcher Switching Characteristics
R
PLLIN
I
PLLLPF
PLLIN Pull-Down Current Source
Phase Detector Output Current
Sourcing Capability
Sinking Capability
TG1↓ vs PLLIN↓
TG1↓ vs PLLIN↓
TG2↓ vs PLLIN↓
TG2↓ vs PLLIN↓
Shutdown Threshold
Floating
90° Phase Threshold
Minimum TG Duty Cycle
Maximum TG Duty Cycle
TG Minimum Pulse Width
BG Minimum Pulse Width
Driver Nonoverlap
TG High R
DS(ON)
TG Low R
DS(ON)
BG High R
DS(ON)
BG Low R
DS(ON)
V
PLLIN
= 0V
V
PLLIN
= 0V, V
CMPIN
= 0.6V (Note 9)
(Notes 7, 10)
V
CMPIN
= 0V (Note 9)
No Load
I
OUT
= 100mA (Note 7)
10
–15
15
0
90
180
270
1.2
3.5
86
1.7
2.0
4.0
89
50
400
30
1.6
1.3
1.8
0.7
80
2.20
1.80
2.50
1.00
Phase
V
PHASEMD
4.5
0
92
DC
MIN
DC
MAX
t
ON(MIN)
t
NOV
R
DS(ON)
q
q
ns
Ω
Ω
Ω
Ω
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
The LTC3802 is guaranteed to meet performance specifications
from 0°C to 70°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls.
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:
To ensure proper operation, PV
CC
and BV
CC
(V
BOOST
– V
SW
) must
be greater than V
GS(ON)
of the external MOSFETs.
Note 5:
Supply current in normal operation is dominated by the current
needed to charge and discharge the external MOSFET gates. This current
will vary with supply voltage and the external MOSFETs used.
Note 6:
Supply current in shutdown is dominated by external MOSFET
leakage and may be significantly higher than the quiescent current drawn
by the LTC3802, especially at elevated temperature.
Note 7:
Guaranteed by design, not subject to test.
Note 8:
Rise and fall times are measured using 10% and 90% levels. Delay
and nonoverlap times are measured using 50% levels.
Note 9:
If V
CMPIN
is less than 90% of its nominal value, BG minimum
pulse width is limited to 400ns.
Note 10:
The LTC3802 leading edge modulation architecture does not
have a minimum TG pulse width requirement. The TG minimum pulse
width is limited by the rise and fall times.
3802f
4
LTC3802
TYPICAL PERFOR A CE CHARACTERISTICS
Efficiency vs I
OUT
100
95
90
85
EFFICIENCY (%)
Burst Mode
OPERATION
70
65
60
55
50
45
40
0.1
1
I
OUT
(A)
3802 G01
90
88
86
84
82
80
0
V
OUT
= 2.5V
I
OUT
= 10A
V
OUT
(V)
75
CONTINUOUS
MODE
EFFICIENCY (%)
80
V
IN
= 12V
V
OUT
= 3.3V
T
A
= 25°C
CIRCUIT ON THE FIRST PAGE
OF THIS DATA SHEET
10
100
Line Regulation
2.5125
V
CC
= 5V
I
OUT
= 5A
T
A
= 25°C
0.5
0.4
0.3
0.2
606.0
604.8
603.6
602.4
2.5075
0
V
FB
(mV)
V
OUT
(V)
2.5025
2.4975
2.4925
2.4875
0
5
10
15
V
IN
(V)
20
25
30
3802 G04
V
FB
vs V
CC
Supply Voltage
603.0
602.4
601.8
601.2
T
A
= 25°C
0.5
0.4
0.3
0.2
0.1
0
V
FB
(mV)
600.6
600.0
599.4
598.8
598.2
597.6
597.0
3
3.5
5
4.5
4
5.5
V
CC
SUPPLY VOLTAGE (V)
6
3802 G06
U W
Efficiency vs V
IN
100
T
A
= 25°C
98 CIRCUIT ON THE FIRST PAGE
OF THIS DATA SHEET
96
94
92
V
OUT
= 2.5V
I
OUT
= 5A
2.5125
Load Regulation
V
IN
= 12V
T
A
= 25°C
CIRCUIT ON THE FIRST PAGE
2.5075
OF THIS DATA SHEET
2.5025
0.5
0.4
0.3
0.2
0.1
0
–0.1
–0.2
2.4925
–0.3
–0.4
∆V
OUT
(%)
2.4975
5
10
15
V
IN
(V)
20
25
30
3802 G02
2.4875
0
5
10
I
OUT
(A)
15
–0.5
20
3802 G03
V
FB
vs Temperature
V
CC
= 5V
1.0
0.8
0.6
0.4
0.2
0
0.1
601.2
600.0
598.8
597.6
596.4
595.2
–0.1
–0.2
–0.3
–0.4
–0.5
–0.1
–0.2
–0.3
–0.4
–0.5
∆V
OUT
(%)
∆V
FB
(%)
–0.2
–0.4
–0.6
–0.8
50
25
0
75
TEMPERATURE (°C)
100
–1.0
125
∆V
FB
(%)
594.0
–50 –25
LTC1323 • TPC05
Line Feedforward Transient
V
OUT
2.5V
(NO LOAD)
AC 50mV/DIV
V
COMP
AC 50mV/DIV
V
IN
5V TO 15V
STEP
5V/DIV
C
IN
: 1µF/50V
×6
10µs/DIV
SANYO 35CV220AX
3802 G07
3802f
5
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