Datasheet

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