lt3781 Linear Technology Corporation, lt3781 Datasheet - Page 2

• Manufacturer Part Number: lt3781
• Description: Bootstrap Start Dual Transistor Synchronous Forward Controller
• Manufacturer: Linear Technology Corporation

ABSOLUTE AXI U RATI GS
(Note 1)
LT3781
Power Supply (V
Topside Supply (V
Topside Reference Pin (V
SHDN Pin Voltage ........................... –0.3V to V
All Other Input Voltages .............. –0.3V to 5V
5V
FSET Pin Current ...................................... –2mA to 5mA
All Other Input Pin Currents ...................... –2mA to 2mA
Operating Ambient
Operating Junction
Temperature Range ...............................–40 C to 125 C
Storage Temperature Range ..................–65 C to 150 C
Lead Temperature (Soldering, 10 sec).................. 300 C
ELECTRICAL CHARACTERISTICS
The
V
SYMBOL
Supply and Protection
V
V
I
V
V
I
V
V
5V External Reference
V
I
R
2
CC
SS
5VREFSC
CCUVLO
CCSHDN
BST
SHDN
SS
BSTUVLO
5VREF
CC
5VREF
Low Impedance Source Voltage ............. –0.3V to 20V
Shutdown Mode:
REF
Temperature Range (Note 4) ...............–40 C to 85 C
= V
(Supply Self-Regulates to 18V)
Maximum Input Current ............................... 20mA
V
denotes specifications which apply over the full operating temperature range, otherwise specifications are T
BST
Pin Sink Current ......................................... 10mA
BSTREF
PARAMETER
Undervoltage Lockout Threshold
Shutdown Mode Shunt Regulator
DC Active Supply Current
DC Active UVLO Supply Current
DC Standby Supply Current
DC Active Supply Current
DC Standby Supply Current
Shutdown Rising Threshold
Shutdown Threshold Hysteresis
Soft-Start Charge Current
Soft-Start Reset Threshold
Boost Undervoltage Lockout
(V
Boost UVLO Hysteresis
5V Reference Voltage
Short-Circuit Current
Output Impedance
= 12V, V
BST
-BSTREF)
– 0.3V to V
CC
BSTREF
W
BST
)
) ....................................................
= 0V, V
BSTREF
BSTREF
W W
VC
= 2V, V
) ............... –0.6V to 75V
+20V (V
FB
= V
BST(MAX)
REF
U
CONDITIONS
Falling Edge
Rising Edge
100 A < I
(Note 2)
V
V
TG Logic High (Note 2)
V
V
Falling Edge
Rising Edge
0 (I
Source, I
0 (I
SHDN
SHDN
SHDN
SS
REF
= 1.25V, C
CC
= 2V
5VREF
5VREF
= 90V)
= 1.35V, V
< 0.3V
< 0.3V
+ 0.3V
+ 0.3V
VC
VCC
– I
– I
= 0
VC
VC
TG
10mA
) < 20mA
) < 20mA
CC
= C
= 8V
PACKAGE/ORDER I FOR ATIO
Consult LTC Marketing for parts specified with wider operating temperature ranges.
BG
THERM
SHDN
SGND
5V
OVLO
SYNC
= C
FSET
V
REF
SS
V
FB
C
SG
T
JMAX
20-LEAD PLASTIC SSOP
10
1
2
3
4
5
6
7
8
9
= 1000pF.
= 125 C,
G PACKAGE
TOP VIEW
JA
= 90 C/W
20
19
18
17
16
15
14
13
12
11
V
TG
BSTREF
NC
NC
BG
PWRGND
V
SG
SENSE
BST
CC
16.5
1.15
4.85
4.80
MIN
100
–14
8.0
5.7
6.5
0.3
13
20
U
14.5
1.25
TYP
800
150
– 10
225
8.4
5.0
0.1
6.4
7.0
0.6
5.0
18
17
16
45
1
ORDER PART
LT3781EG
LT3781IG
NUMBER
A
= 25 C.
W
1200
MAX
19.9
1.35
5.10
5.15
200
8.6
8.5
7.1
7.5
– 6
16
22
25
30
UNITS
U
3781f
mA
mA
mA
mV
mV
mA
V
V
V
A
A
A
V
A
V
V
V
V
V