LTC3780
High Efficiency, Synchronous,
4-Switch Buck-Boost Controller
DESCRIPTIO
The LTC
®
3780 is a high performance buck-boost switch-
ing regulator controller that operates from input voltages
above, below or equal to the output voltage. The constant
frequency current mode architecture allows a phase-
lockable frequency of up to 400kHz. With a wide 4V to 30V
(36V maximum) input and output range and seamless
transfers between operating modes, the LTC3780 is ideal
for automotive, telecom and battery-powered systems.
The operating mode of the controller is determined through
the FCB pin. For boost operation, the FCB mode pin can
select among Burst Mode
®
operation, Discontinuous mode
and Forced Continuous mode. During buck operation, the
FCB mode pin can select among Skip-Cycle mode, Discon-
tinuous mode and Forced Continuous mode. Burst Mode
operation and Skip-Cycle mode provide high efficiency
operation at light loads while Forced Continuous mode
and Discontinuous mode operate at a constant frequency.
Fault protection is provided by an output overvoltage
comparator and internal foldback current limiting. A Power
Good output pin indicates when the output is within 7.5%
of its designed set point.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Protected by U.S. Patents, including 5481178, 6304066, 5929620, 5408150, 6580258,
patent pending on current mode architecture and protection
FEATURES
■
■
■
■
■
■
■
■
■
■
■
■
■
■
■
Single Inductor Architecture Allows V
IN
Above,
Below or Equal to V
OUT
Wide V
IN
Range: 4V to 36V Operation
Synchronous Rectification: Up to 98% Efficiency
Current Mode Control
±1%
Output Voltage Accuracy: 0.8V < V
OUT
< 30V
Phase-Lockable Fixed Frequency: 200kHz to 400kHz
Power Good Output Voltage Monitor
Internal LDO for MOSFET Supply
Quad N-Channel MOSFET Synchronous Drive
V
OUT
Disconnected from V
IN
During Shutdown
Adjustable Soft-Start Current Ramping
Foldback Output Current Limiting
Selectable Low Current Modes
Output Overvoltage Protection
Available in 24-Lead SSOP and Exposed Pad
(5mm
×
5mm) 32-Lead QFN Packages
APPLICATIO S
■
■
■
■
■
Automotive Systems
Telecom Systems
DC Power Distribution Systems
High Power Battery-Operated Devices
Industrial Control
TYPICAL APPLICATIO
V
IN
4V TO 36V
22µF
50V
CER
High Efficiency Buck-Boost Converter
+
4.7µF
V
IN
PGOOD INTV
CC
TG2
0.1µF
BOOST2
SW2
LTC3780
BG2
2200pF
20k
0.1µF
I
TH
SS
TG1
BOOST1
SW1
0.1µF
1µF
CER
100µF
16V
CER
V
OUT
12V
5A
EFFICIENCY (%)
BG1
PLLIN
RUN
V
OSENSE
ON/OFF
7.5k
105k
1%
SGND
FCB
SENSE
+
SENSE
–
PGND
1000pF
0.010Ω
2µH
3780 TA01
U
U
U
Efficiency and Power Loss
V
OUT
= 12V, I
LOAD
= 5A
100
95
90
85
80
75
70
0
5
10
20
15
V
IN
(V)
25
30
35
10
9
8
7
6
5
4
3
2
1
0
POWER LOSS (W)
3780 TA01b
3780f
1
LTC3780
ABSOLUTE
MAXIMUM
RATINGS
(Note 1)
Input Supply Voltage (V
IN
)........................ –0.3V to 36V
Topside Driver Voltages
(BOOST1, BOOST2) .................................. –0.3V to 42V
Switch Voltage (SW1, SW2) ........................ –5V to 36V
INTV
CC
, EXTV
CC
, RUN, SS, (BOOST – SW1),
(BOOST2 – SW2), PGOOD .......................... –0.3V to 7V
PLLIN Voltage .......................................... –0.3V to 5.5V
PLLFLTR Voltage ...................................... –0.3V to 2.7V
FCB, STBYMD Voltages ....................... –0.3V to INTV
CC
I
TH
, V
OSENSE
Voltages .............................. –0.3V to 2.4V
Peak Output Current <10ms (TG1, TG2, BG1, BG2) .. 3A
INTV
CC
Peak Output Current ................................ 40mA
Operating Temperature Range (Note 7)
LTC3780E ........................................... – 40°C to 85°C
LTC3780I ............................................ – 40°C to 85°C
Junction Temperature (Note 2) ............................ 125°C
Storage Temperature Range .................. –65°C to 125°C
Lead Temperature (Soldering, 10 sec)
SSOP Only ........................................................ 300°C
PACKAGE/ORDER INFORMATION
TG1
TOP VIEW
PGOOD
SS
SENSE
+
SENSE
–
I
TH
V
OSENSE
SGND
RUN
FCB
1
2
3
4
5
6
7
8
9
24 BOOST1
23 TG1
22 SW1
21 V
IN
20 EXTV
CC
19 INTV
CC
18 BG1
17 PGND
16 BG2
15 SW2
14 TG2
13 BOOST2
BOOST1
PGOOD
ORDER PART
NUMBER
NC
NC
NC
LTC3780EG
LTC3780IG
NC
SS
PLLFLTR 10
PLLIN 11
STBYMD 12
PLLIN
STBYMD
BOOST2
G PACKAGE
24-LEAD PLASTIC SSOP
T
JMAX
= 125°C,
θ
JA
= 130°C/W
UH PACKAGE
32-LEAD (5mm
×
5mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 34°C/W
EXPOSED PAD (PIN 33) IS SGND
(MUST BE SOLDERED TO PCB)
Consult LTC Marketing for parts specified with wider operating temperature ranges.
The
●
indicates specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 15V unless otherwise noted.
SYMBOL
V
OSENSE
I
VOSENSE
V
LOADREG
PARAMETER
Feedback Reference Voltage
Feedback Pin Input Current
Output Voltage Load Regulation
CONDITIONS
I
TH
= 1.2V (Note 3)
(Note 3)
(Note 3)
∆I
TH
= 1.2V to 0.7V
∆I
TH
= 1.2V to 1.8V
●
●
●
ELECTRICAL CHARACTERISTICS
Main Control Loop
TG2
NC
NC
NC
NC
2
U
U
W
W W
U
W
TOP VIEW
ORDER PART
NUMBER
24 SW1
23 V
IN
22 EXTV
CC
21 INTV
CC
20 BG1
19 PGND
18 BG2
17 SW2
32 31 30 29 28 27 26 25
SENSE
+
1
SENSE
–
2
LTC3780EUH
LTC3780IUH
I
TH
3
V
OSENSE
4
SGND 5
RUN 6
FCB 7
PLLFTR 8
9 10 11 12 13 14 15 16
33
UH PART
MARKING
3780
3780I
MIN
0.792
TYP
0.800
–5
0.1
–0.1
MAX
0.808
–50
0.5
–0.5
UNITS
V
nA
%
%
3780f
LTC3780
The
●
indicates specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 15V unless otherwise noted.
SYMBOL
V
REF(LINEREG)
g
m(EA)
g
m(GBW)
I
Q
PARAMETER
Reference Voltage Line Regulation
Error Amplifier Transconductance
Error Amplifier GBW
Input DC Supply Current
Normal
Standby
Shutdown Supply Current
Forced Continuous Threshold
Forced Continuous Pin Current
Burst Inhibit (Constant Frequency)
Threshold
Undervoltage Reset
Feedback Overvoltage Lockout
Sense Pins Total Source Current
Start-Up Threshold
Keep-Alive Power-On Threshold
Maximum Duty Factor
RUN Pin On Threshold
Soft-Start Charge Current
Maximum Current Sense Threshold
V
FCB
= 0.85V
Measured at FCB Pin
V
IN
Falling
Measured at V
OSENSE
Pin
V
SENSE–
= V
SENSE+
= 0V
V
STBYMD
Rising
V
STBYMD
Rising, V
RUN
= 0V
% Switch C On
% Switch A On (in Dropout)
V
RUN
Rising
V
RUN
= 2V
Boost: V
OSENSE
= V
REF
– 50mV
Buck: V
OSENSE
= V
REF
– 50mV
Discontinuous Mode
C
LOAD
= 3300pF (Note 5)
C
LOAD
= 3300pF (Note 5)
C
LOAD
= 3300pF (Note 5)
C
LOAD
= 3300pF (Note 5)
C
LOAD
= 3300pF Each Driver
C
LOAD
= 3300pF Each Driver
C
LOAD
= 3300pF Each Driver
C
LOAD
= 3300pF Each Driver
C
LOAD
= 3300pF Each Driver
C
LOAD
= 3300pF Each Driver
●
●
●
ELECTRICAL CHARACTERISTICS
CONDITIONS
V
IN
= 4V to 30V, I
TH
= 1.2V (Note 3)
I
TH
= 1.2V, Sink/Source = 3µA (Note 3)
(Note 4)
V
RUN
= 0V, V
STBYMD
> 2V
V
RUN
= 0V, V
STBYMD
= Open
MIN
TYP
0.002
0.32
0.6
2400
1500
55
MAX
0.02
UNITS
%/V
mS
MHz
µA
µA
µA
V
µA
V
V
V
µA
V
V
%
%
70
0.84
–0.1
5.5
4
0.88
V
FCB
I
FCB
V
BINHIBIT
UVLO
V
OVL
I
SENSE
V
STBYMD(START)
V
STBYMD(KA)
DF MAX, BUCK
V
RUN(ON)
I
SS
V
SENSE(MAX)
0.76
–0.30
0.800
–0.18
5.3
3.8
0.84
0.4
0.86
–380
0.7
1.25
99
99
DF MAX, BOOST Maximum Duty Factor
1
0.5
–95
1.5
1.2
160
–130
–6
50
45
45
55
80
80
80
80
90
90
2
185
–150
V
µA
mV
mV
mV
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
V
SENSE(MIN,BUCK)
Minimum Current Sense Threshold
TG1, TG2 t
r
TG1, TG2 t
f
BG1, BG2 t
r
BG1, BG2 t
f
TG1/BG1 t
1D
BG1/TG1 t
2D
TG2/BG2 t
3D
BG2/TG2 t
4D
Mode
Transition 1
Mode
Transition 2
TG Rise Time
TG Fall Time
BG Rise Time
BG Fall Time
TG1 Off to BG1 On Delay,
Switch C On Delay
BG1 Off to TG1 On Delay,
Synchronous Switch D On Delay
TG2 Off to BG2 On Delay,
Synchronous Switch B On Delay
BG2 Off to TG2 On Delay,
Switch A On Delay
BG1 Off to BG2 On Delay,
Switch A On Delay
BG2 Off to BG1 On Delay,
Synchronous Switch D On Delay
3780f
3
LTC3780
The
●
indicates specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 15V unless otherwise noted.
SYMBOL
t
ON(MIN,BOOST)
t
ON(MIN,BUCK)
PARAMETER
Minimum On-Time for Main Switch in
Boost Operation
Minimum On-Time for Synchronous
Switch in Buck Operation
Internal V
CC
Voltage
Internal V
CC
Load Regulation
EXTV
CC
Switchover Voltage
EXTV
CC
Switchover Hysteresis
EXTV
CC
Switch Drop Voltage
Nominal Frequency
Lowest Frequency
Highest Frequency
PLLIN Input Resistance
Phase Detector Output Current
f
PLLIN
< f
OSC
f
PLLIN
> f
OSC
V
OSENSE
Rising
V
OSENSE
Falling
V
OSENSE
Returning
I
PGOOD
= 2mA
V
PGOOD
= 5V
5.5
–5.5
I
CC
= 20mA, V
EXTVCC
= 6V
V
PLLFLTR
= 1.2V
V
PLLFLTR
= 0V
V
PLLFLTR
= 2.4V
260
170
340
CONDITIONS
Switch C (Note 6)
Switch B (Note 6)
MIN
TYP
200
180
MAX
240
220
UNITS
ns
ns
ELECTRICAL CHARACTERISTICS
Internal V
CC
Regulator
V
INTVCC
∆V
LDO(LOADREG)
V
EXTVCC
∆V
EXTVCC(HYS)
∆V
EXTVCC
f
NOM
f
LOW
f
HIGH
R
PLLIN
I
PLLLPF
PGOOD Output
∆V
FBH
∆V
FBL
∆V
FB(HYST)
V
PGL
I
PGOOD
PGOOD Upper Threshold
PGOOD Lower Threshold
PGOOD Hysteresis
PGOOD Low Voltage
PGOOD Leakage Current
7.5
–7.5
2.5
0.1
0.3
±1
10
–10
%
%
%
V
µA
7V < V
IN
< 30V, V
EXTVCC
= 5V
I
CC
= 0mA to 20mA, V
EXTVCC
= 5V
I
CC
= 20mA, V
EXTVCC
Rising
●
●
5.7
5.4
6
0.2
5.7
200
150
300
200
400
50
–15
15
6.3
2
V
%
V
mV
300
330
220
440
mV
kHz
kHz
kHz
kΩ
µA
µA
Oscillator and Phase-Locked Loop
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
T
J
for the QFN package is calculated from the temperature T
A
and
power dissipation P
D
according to the following formula:
T
J
= T
A
+ (P
D
• 34°C/W)
Note 3:
The IC is tested in a feedback loop that servos V
ITH
to a specified
voltage and measures the resultant V
OSENSE
.
Note 4:
Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency.
Note 5:
Rise and fall times are measured using 10% and 90% levels. Delay
times are measured using 50% levels.
Note 6:
The minimum on-time condition is specified for an inductor peak-
to-peak ripple current
≥
40% of I
MAX
(see minimum on-time
considerations in the Applications Information section).
Note 7:
The LTC3780E is guaranteed to meet performance specifications
from 0°C to 85°C. Performance over the –40°C to 85°C operating
temperature range is assured by design, characterization and correlation
with statistical process controls. The LTC3780I is guaranteed and tested
over the – 40°C to 85°C operating temperature range.
3780f
4
LTC3780
TYPICAL PERFOR A CE CHARACTERISTICS
Efficiency vs Output Current
(Boost Operation)
100
BURST
90
DCM
EFFICIENCY (%)
EFFICIENCY (%)
DCM
70
60
50
CCM
EFFICIENCY (%)
80
70
CCM
60
50
40
0.01
V
IN
= 6V
V
OUT
= 12V
0.1
I
LOAD
(A)
3780 G01
1
Supply Current vs Input Voltage
2500
V
FCB
= 0V
2000
SUPPLY CURRENT (µA)
6.5
6.0
STANDBY
1500
5.5
5.0
4.5
4.0
EXTV
CC
VOLTAGE DROP (mV)
INTV
CC
VOLTAGE (V)
1000
500
SHUTDOWN
0
0
5
20
15
10
25
INPUT VOLTAGE (V)
30
35
INTV
CC
and EXTV
CC
Switch
Voltage vs Temperature
6.05
5
INTV
CC
AND EXTV
CC
SWITCH VOLTAGE (V)
6.00
5.95
5.90
5.85
5.80
5.75
5.70
5.65
5.60
5.55
–50 –25
EXTV
CC
SWITCH RESISTANCE (Ω)
INTV
CC
VOLTAGE
3
NORMALIZED V
OUT
(%)
EXTV
CC
SWITCHOVER THRESHOLD
50
25
0
75
TEMPERATURE (°C)
U W
10
3780 G04
T
A
= 25°C unless otherwise noted.
Efficiency vs Output Current
(Buck Operation)
100
Efficiency vs Output Current
100
BURST
90
80
90
SC
80
70
60
50
V
IN
= 12V
V
OUT
= 12V
0.1
I
LOAD
(A)
3780 G02
CCM
DCM
40
0.01
1
10
40
0.01
V
IN
= 18V
V
OUT
= 12V
0.1
I
LOAD
(A)
3780 G03
1
10
Internal 6V LDO Line Regulation
120
100
80
60
40
20
0
EXTV
CC
Voltage Drop
3.5
0
5
20
15
25
10
INPUT VOLTAGE (V)
30
35
1
10
20
30
CURRENT (mA)
40
50
3780 G06
3780 G05
EXTV
CC
Switch Resistance
vs Temperature
0
Load Regulation
V
IN
= 18V
4
–0.1
–0.2
V
IN
= 12V
2
–0.3
V
IN
= 6V
–0.4
FCB = 0V
V
OUT
= 12V
0
1
3
2
LOAD CURRENT (A)
4
5
3780 G09
1
100
125
0
–50
–25
50
25
0
75
TEMPERATURE (°C)
100
125
–0.5
3780 G07
3780 G08
3780f
5
单片机
京公网安备 11010802033920号
Copyright © 2005-2026 EEWORLD.com.cn, Inc. All rights reserved
电子工程世界
