Datasheet
2
LT1777
ABSOLUTE MAXIMUM RATINGS
W
WW
U
WU
U
PACKAGE
/
O
RDER I FOR ATIO
(Note 1)
Supply Voltage ....................................................... 48V
Switch Voltage (V
IN
– V
SW
) (Note 4) ...................... 51V
SHDN, SYNC Pin Voltage.......................................... 7V
V
CC
Pin Voltage ...................................................... 30V
FB Pin Voltage ........................................................ 3.0V
Operating Junction Temperature Range
LT1777C............................................... 0°C to 125°C
LT1777I ........................................... –40°C to 125°C
Storage Temperature Range ................ –65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
TOP VIEW
S PACKAGE
16-LEAD PLASTIC SO
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
GND*
NC
SHDN
V
CC
V
D
V
SW
SGND
GND*
GND*
NC
V
C
FB
SYNC
NC
V
IN
GND*
T
JMAX
= 125°C, θ
JA
= 50°C/W*
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are at T
J
= 25°C.
V
IN
= 24V, V
SW
Open, V
CC
= 5V, V
C
= 1.4V unless otherwise noted.
ORDER PART
NUMBER
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 2.5 3.5 mA
● 4.5 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 ∆I
C
= ±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
≤ 48V ● 0.01 %/V
Voltage Gain 200 600 V/V
*FOUR CORNER PINS ARE
FUSED TO INTERNAL DIE
ATTACH PADDLE FOR HEAT
SINKING. CONNECT THESE
FOUR PINS TO EXPANDED PC
LANDS FOR PROPER HEAT
SINKING.
LT1777CS
LT1777IS
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