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LT1676CS8#PBF

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P16
1
LT1676
Wide Input Range,
High Efficiency, Step-Down
Switching Regulator
■
Wide Input Range: 7.4V to 60V
■
700mA Peak Switch Current Rating
■
Adaptive Switch Drive Maintains Efficiency at High
Load Without Pulse Skipping at Light Load
■
True Current Mode Control
■
100kHz Fixed Operating Frequency
■
Synchronizable to 250kHz
■
Low Supply Current in Shutdown: 30µA
■
Available in 8-Pin SO and PDIP Packages
■
Automotive DC/DC Converters
■
Telecom 48V Step-Down Converters
■
Cellular Phone Battery Charger Accessories
■
IEEE 1394 Step-Down Converters
The LT
®
1676 is a wide input range, high efficiency Buck
(step-down) switching regulator. The monolithic die in-
cludes all oscillator, control and protection circuitry. The
part can accept input voltages as high as 60V and contains
an output switch rated at 700mA peak current. Current
mode control offers excellent dynamic input supply rejec-
tion and short-circuit protection.
The LT1676 contains several features to enhance effi-
ciency. The internal control circuitry is normally powered
via the V
CC
pin, thereby minimizing power drawn directly
from the V
IN
supply (see Applications Information). The
action of the LT1676 switch circuitry is also load depen-
dent. At medium to high loads, the output switch circuitry
maintains high rise time for good efficiency. At light loads,
rise time is deliberately reduced to avoid pulse skipping
behavior.
The available SO-8 package and 100kHz switching fre-
quency allow for minimal PC board area requirements.
Figure 1
, LTC and LT are registered trademarks of Linear Technology Corporation.
39µF
63V
1676 F01
V
IN
V
CC
V
SW
LT1676
FB
V
C
SHDN
SYNC
2
5
4
3
7
8
1
6
GND
+
100µF
10V
+
MBR160
36.5k
1%
5V
400mA
12.1k
1%
22k
220µH*
2200pF
V
IN
8V TO 50V
100pF
*65T #30 ON MAGNETICS
MPP #55030
I
LOAD
(mA)
1
60
EFFICIENCY (%)
70
80
90
10 100 1000
1676 TA01
50
40
30
20
V
IN
= 12V
V
IN
= 24V
V
IN
= 36V
V
IN
= 48V
Efficiency vs V
IN
and I
LOAD
FEATURES
DESCRIPTIO
U
APPLICATIO S
U
TYPICAL APPLICATIO
U
2
LT1676
ABSOLUTE MAXIMUM RATINGS
W
WW
U
PACKAGE/ORDER INFORMATION
W
U
U
ORDER PART
NUMBER
Consult factory for Military grade parts.
1676
1676I
LT1676CN8
LT1676CS8
LT1676IN8
LT1676IS8
S8 PART MARKING
T
JMAX
= 125°C, θ
JA
= 130°C/W (N8)
T
JMAX
= 125°C, θ
JA
= 110°C/W (S8)
1
2
3
4
8
7
6
5
TOP VIEW
V
C
FB
SYNC
V
IN
SHDN
V
CC
V
SW
GND
N8 PACKAGE
8-LEAD PDIP
S8 PACKAGE
8-LEAD PLASTIC SO
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Power Supplies
V
IN(MIN)
Minimum Input Voltage 6.7 7.0 V
● 7.4 V
I
VIN
V
IN
Supply Current V
C
= 0V 620 800 µA
● 900 µA
I
VCC
V
CC
Supply Current V
C
= 0V 3.2 4.0 mA
● 5.0 mA
V
VCC
V
CC
Dropout Voltage (Note 2) ● 2.8 3.1 V
Shutdown Mode I
VIN
V
SHDN
= 0V 30 50 µA
● 75 µA
Feedback Amplifier
V
REF
Reference Voltage 1.225 1.240 1.255 V
● 1.215 1.265 V
I
IN
FB Pin Input Bias Current 600 1500 nA
g
m
Feedback Amplifier Transconductance ∆lc = ±10µA 400 650 1000 µmho
● 200 1500 µmho
I
SRC
, I
SNK
Feedback Amplifier Source or Sink Current 60 100 170 µA
● 45 220 µA
V
CL
Feedback Amplifier Clamp Voltage 2.0 V
Reference Voltage Line Regulation 12V ≤ V
IN
≤ 60V ● 0.01 %/V
Voltage Gain 200 600 V/V
Output Switch
V
ON
Output Switch On Voltage I
SW
= 0.5A 1.0 1.5 V
I
LIM
Switch Current Limit (Note 3) ● 0.55 0.70 1.0 A
Current Amplifier
Control Pin Threshold Duty Cycle = 0% 0.9 1.1 1.25 V
Control Voltage to Switch Transconductance 2 A/V
(Note 1)
Supply Voltage ........................................................ 60V
Switch Voltage......................................................... 60V
SHDN, SYNC Pin Voltage........................................... 7V
V
CC
Pin Voltage ....................................................... 30V
FB Pin Voltage ........................................................... 3V
Operating Junction Temperature Range
LT1676C................................................0°C to 125°C
LT1676I............................................ –40°C to 125°C
Storage Temperature Range ................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec)..................300°C
V
IN
= 48V, V
SW
open, V
CC
= 5V, V
C
= 1.4V unless otherwise noted.
The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are T
A
= 25°C.
ELECTRICAL CHARACTERISTICS
3
LT1676
ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Timing
f Switching Frequency 90 100 110 kHz
● 85 115 kHz
Maximum Switch Duty Cycle ● 85 90 %
t
ON(MIN)
Minimum Switch On Time High dV/dt Mode, R
L
= 50Ω (Note 4) 300 ns
Boost Operation
V
C
Pin Boost Threshold 1.35 V
dV/dt Below Threshold 0.2 V/ns
dV/dt Above Threshold 1.6 V/ns
Sync Function
Minimum Sync Amplitude ● 1.5 2.2 V
Synchronization Range ● 130 250 kHz
SYNC Pin Input R 40 kΩ
SHDN Pin Function
V
SHDN
Shutdown Mode Threshold 0.5 V
● 0.2 0.8 V
Upper Lockout Threshold Switching Action On 1.260 V
Lower Lockout Threshold Switching Action Off 1.245 V
I
SHDN
Shutdown Pin Current V
SHDN
= 0V 12 20 µA
V
SHDN
= 1.25V 2.5 10 µA
V
IN
= 48V, V
SW
open, V
CC
= 5V, V
C
= 1.4V unless otherwise noted.
The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are T
A
= 25°C.
TEMPERATURE (°C)
–50
7.4
7.2
7.0
6.8
6.6
6.4
6.2
6.0
25 75
LT1676 G01
–25 0
50 100 125
INPUT VOLTAGE (V)
Minimum Input Voltage vs
Temperature
SWITCH CURRENT (mA)
0
SWITCH VOLTAGE (V)
1.50
1.25
1.00
0.75
0.50
0.25
0
300 500
1676 G02
100 200
400 600 700
125°C
–55°C
25°C
DUTY CYCLE (%)
0
SWITCH CURRENT LIMIT (mA)
1000
800
600
400
200
0
80
1676 G03
2010 30 50 70 90
40
60
100
T
A
= 25°C
Switch Current Limit vs
Duty Cycle
Switch-On Voltage vs
Switch Current
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: Control circuitry powered from V
CC
.
Note 3: Switch current limit is DC trimmed and tested in production.
Inductor dl/dt rate will cause a somewhat higher current limit in actual
application.
Note 4: Minimum switch on time is production tested with a 50Ω resistive
load to ground.
TYPICAL PERFORMANCE CHARACTERISTICS
UW
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LT1676CS8#PBF

Mfr. #:
Buy LT1676CS8#PBF
Manufacturer:
Analog Devices / Linear Technology
Description:
Switching Voltage Regulators Wide In Rng, Hi Eff, Buck Sw Reg
Lifecycle:
New from this manufacturer.
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