OMO ElectronicOMO Electronic
Expand menu
Hello, Sign inMy Account
0 Cart

LTC3778EF#PBF

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24
1
LTC3778
3778f
FEATURES
DESCRIPTIO
U
APPLICATIO S
U
TYPICAL APPLICATIO
U
Wide Operating Range,
No R
SENSE
TM
Step-Down Controller
■
Wide V
IN
Range: 4V to 36V
■
Sense Resistor Optional
■
True Current Mode Control
■
2% to 90% Duty Cycle at 200kHz
■
t
ON(MIN)
≤ 100ns
■
Stable with Ceramic C
OUT
■
Dual N-Channel MOSFET Synchronous Drive
■
Power Good Output Voltage Monitor
■
±1% 0.6V Reference
■
Adjustable Current Limit
■
Adjustable Switching Frequency
■
Programmable Soft-Start
■
Output Overvoltage Protection
■
Optional Short-Circuit Shutdown Timer
■
Micropower Shutdown: I
Q
≤ 30µA
■
Available in a 1mm 20-Lead TSSOP Package
■
Notebook and Palmtop Computers, PDAs
■
Battery Chargers
■
Distributed Power Systems
■
DDR Memory Power Supply
■
Automobile DC Power Supply
The LTC
®
3778 is a synchronous step-down switching
regulator controller for computer memory, automobile
and other DC/DC power supplies. The controller uses a
valley current control architecture to deliver very low duty
cycles without requiring a sense resistor. Operating fre-
quency is selected by an external resistor and is compen-
sated for variations in V
IN
and V
OUT
.
Discontinuous mode operation provides high efficiency
operation at light loads. A forced continuous control pin
reduces noise and RF interference, and can assist second-
ary winding regulation when the main output is lightly
loaded. SENSE
+
and
SENSE
–
pins provide true Kelvin
sensing across the optional sense resistor or the
sychronous MOSFET.
Fault protection is provided by internal foldback current
limiting, an output overvoltage comparator, optional short-
circuit shutdown timer and input undervoltage lockout.
Soft-start capability for supply sequencing is accom-
plished using an external timing capacitor. The regulator
current limit level is user programmable. Wide supply
range allows operation from 4V to 36V at the input and
from 0.6V up to (0.9)V
IN
at the output.
, LTC and LT are registered trademarks of Linear Technology Corporation.
No R
SENSE
is a trademark of Linear Technology Corporation.
Figure 1. High Efficiency Step-Down Converter
Efficiency vs Load Current
LOAD CURRENT (A)
0.01
EFFICIENCY (%)
80
90
3778 F01b
70
60
0.1
1
10
100
V
IN
= 5V
V
IN
= 25V
+
D
B
CMDSH-3
D1
B340A
L1
1.8µH
C
VCC
4.7µF
C
IN
10µF
35V
×3
V
IN
5V TO 28V
V
OUT
2.5V
10A
+
C
OUT
180µF
4V
×2
M2
Si4874
3778 F01a
M1
Si4884
R
ON
1.4M
C
SS
0.1µF
I
ON
V
IN
TG
SW
BOOST
RUN/SS
I
TH
SGND
INTV
CC
BG
PGND
SENSE
–
SENSE
+
V
FB
PGOOD
C
B
0.22µF
R
C
20k
LTC3778
C
C
500pF
R2
40.2k
R1
12.7k
DRV
CC
2
LTC3778
3778f
(Note 1)
Input Supply Voltage (V
IN
, I
ON
)..................36V to –0.3V
Boosted Topside Driver Supply Voltage
(BOOST) ................................................... 42V to –0.3V
SENSE
+
,
SW Voltage.................................... 36V to –5V
DRV
CC
, EXTV
CC
, (BOOST – SW),
FCB,
RUN/SS, PGOOD Voltages .................... 7V to –0.3V
V
ON,
V
RNG
Voltages................... INTV
CC
+ 0.3V to –0.3V
I
TH
, V
FB
Voltages...................................... 2.7V to –0.3V
TG, BG, INTV
CC
Peak Currents.................................. 2A
TG, BG, INTV
CC
RMS Currents ............................ 50mA
Operating Ambient Temperature
Range (Note 4) ................................... –40°C to 85°C
Junction Temperature (Note 2)............................ 125°C
Storage Temperature Range ................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec)..................300°C
ORDER PART
NUMBER
LTC3778EF
Consult LTC Marketing for parts specified with wider operating temperature ranges.
T
JMAX
= 125°C, θ
JA
= 110°C/W
The ● denotes specifications which apply over the full operating
temperature range, otherwise specifications are T
A
= 25°C. V
IN
= 15V unless otherwise noted.
ABSOLUTE AXI U RATI GS
WWWU
PACKAGE/ORDER I FOR ATIO
UU
W
ELECTRICAL CHARACTERISTICS
1
2
3
4
5
6
7
8
9
10
TOP VIEW
20
19
18
17
16
15
14
13
12
11
RUN/SS
V
ON
PGOOD
V
RNG
I
TH
FCB
SGND
I
ON
V
FB
EXTV
CC
BOOST
TG
SW
SENSE
+
SENSE
–
PGND
BG
DRV
CC
INTV
CC
V
IN
F PACKAGE
20-LEAD PLASTIC TSSOP
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Main Control Loop
I
Q
Input DC Supply Current
Normal 900 2000 µA
Shutdown Supply Current 15 30 µA
V
FB
Feedback Reference Voltage I
TH
= 1.2V (Note 3) ● 0.594 0.600 0.606 V
∆V
FB(LINEREG)
Feedback Voltage Line Regulation V
IN
= 4V to 30V, I
TH
= 1.2V (Note 3) 0.002 %/V
∆V
FB(LOADREG)
Feedback Voltage Load Regulation I
TH
= 0.5V to 1.9V (Note 3) –0.05 –0.3 %
I
FB
Feedback Pin Input Current –5 ±100 nA
g
m(EA)
Error Amplifier Transconductance I
TH
= 1.2V (Note 3) ● 1.4 1.7 2 mS
V
FCB
Forced Continuous Threshold ● 0.57 0.6 0.63 V
I
FCB
Forced Continuous Pin Current V
FCB
= 0.6V –1 –2 µA
t
ON
On-Time I
ON
= 60µA, V
ON
= 1.5V 200 250 300 ns
I
ON
= 60µA, V
ON
= 0V 110 ns
t
ON(MIN)
Minimum On-Time I
ON
= 180µA, V
ON
= 0V 50 100 ns
t
OFF(MIN)
Minimum Off-Time I
ON
= 60µA, V
ON
= 1.5V 250 400 ns
V
SENSE(MAX)
Maximum Current Sense Threshold V
RNG
= 1V, V
FB
= 0.56V ● 113 133 153 mV
V
SENSE
–
– V
SENSE
+
V
RNG
= 0V, V
FB
= 0.56V ● 79 93 107 mV
V
RNG
= INTV
CC
, V
FB
= 0.56V ● 158 186 214 mV
V
SENSE(MIN)
Minimum Current Sense Threshold V
RNG
= 1V, V
FB
= 0.64V 67 mV
V
SENSE
+
– V
SENSE
–
V
RNG
= 0V, V
FB
= 0.64V 47 mV
V
RNG
= INTV
CC
, V
FB
= 0.64V 93 mV
∆V
FB(OV)
Output Overvoltage Fault Threshold 7.5 10 12.5 %
∆V
FB(UV)
Output Undervoltage Fault Threshold 340 400 460 mV
3
LTC3778
3778f
The ● denotes specifications which apply over the full operating
temperature range, otherwise specifications are T
A
= 25°C. V
IN
= 15V unless otherwise noted.
ELECTRICAL CHARACTERISTICS
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
as follows:
LTC3778E: T
J
= T
A
+ (P
D
• 110°C/W)
Note 3: The LTC3778 is tested in a feedback loop that adjusts V
FB
to achieve
a specified error amplifier output voltage (I
TH
).
Note 4: The LTC3778E 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.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
RUN/SS(ON)
RUN Pin Start Threshold ● 0.8 1.5 2 V
V
RUN/SS(LE)
RUN Pin Latchoff Enable Threshold RUN/SS Pin Rising 4 4.5 V
V
RUN/SS(LT)
RUN Pin Latchoff Threshold RUN/SS Pin Falling 3.5 4.2 V
I
RUN/SS(C)
Soft-Start Charge Current –0.5 –1.2 –3 µA
I
RUN/SS(D)
Soft-Start Discharge Current 0.8 1.8 3 µA
V
IN(UVLO)
Undervoltage Lockout Threshold V
IN
Falling ● 3.4 3.9 V
V
IN(UVLOR)
Undervoltage Lockout Threshold V
IN
Rising ● 3.5 4 V
TG R
UP
TG Driver Pull-Up On Resistance TG High 2 3 Ω
TG R
DOWN
TG Driver Pull-Down On Resistance TG Low 2 3 Ω
BG R
UP
BG Driver Pull-Up On Resistance BG High 3 4 Ω
BG R
DOWN
BG Driver Pull-Down On Resistance BG Low 1 2 Ω
TG t
r
TG Rise Time C
LOAD
= 3300pF 20 ns
TG t
f
TG Fall Time C
LOAD
= 3300pF 20 ns
BG t
r
BG Rise Time C
LOAD
= 3300pF 20 ns
BG t
f
BG Fall Time C
LOAD
= 3300pF 20 ns
Internal V
CC
Regulator
V
INTVCC
Internal V
CC
Voltage 6V < V
IN
< 30V, V
EXTVCC
= 4V ● 4.7 5 5.3 V
∆V
LDO(LOADREG)
Internal V
CC
Load Regulation I
CC
= 0mA to 20mA, V
EXTVCC
= 4V –0.1 ±2%
V
EXTVCC
EXTV
CC
Switchover Voltage I
CC
= 20mA, V
EXTVCC
Rising ● 4.5 4.7 V
∆V
EXTVCC
EXTV
CC
Switch Drop Voltage I
CC
= 20mA, V
EXTVCC
= 5V 150 300 mV
∆V
EXTVCC(HYS)
EXTV
CC
Switchover Hysteresis 200 mV
PGOOD Output
∆V
FBH
PGOOD Upper Threshold V
FB
Rising 7.5 10 12.5 %
∆V
FBL
PGOOD Lower Threshold V
FB
Falling – 7.5 –10 –12.5 %
∆V
FB(HYS)
PGOOD Hysteresis V
FB
Returning 1 2.5 %
V
PGL
PGOOD Low Voltage I
PGOOD
= 5mA 0.15 0.4 V
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24

LTC3778EF#PBF

Mfr. #:
Buy LTC3778EF#PBF
Manufacturer:
Analog Devices / Linear Technology
Description:
Switching Voltage Regulators Wide Operating Rng, No RSENSE Buck Cntr
Lifecycle:
New from this manufacturer.
Delivery:
DHL FedEx Ups TNT EMS
Payment:
T/T Paypal Visa MoneyGram Western Union

Products related to this Datasheet