lt3781 Linear Technology Corporation, lt3781 Datasheet - Page 3

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

ELECTRICAL CHARACTERISTICS
SYMBOL
Error Amp
V
I
A
I
V
GBW
Current Sense
A
I
V
t
t
THERM and OVLO Fault Detectors
V
V
t
Oscillator and Synchronization Decoder
f
I
V
f
t
Output Drivers
V
t
V
t
V
t
t
t
The
V
FB
VC
SENSE
D
MIN
D
OSC
FSET
SYNC
H, L
TGr/f
BGr/f
SGr/f
SG-BG
TG-BG
FB
V
VC
V
SENSE
THERM
OVLO
SYNC
TG
BG
SG
CC
= V
denotes specifications which apply over the full operating temperature range, otherwise specifications are T
/
BST
PARAMETER
Error Amplifier Reference Voltage
Feedback Input Current
Error Amplifier Voltage Gain
Error Amplifier Current Limit
Zero Current Output Voltage
Maximum Output Voltage
Gain Bandwidth Product
Amplifier DC Gain
Input Bias Current
Current Limit Threshold
Current Sense to Switch Delay
Switch Minimum On Time
Threshold (Rising Edge)
Threshold Hysteresis
Fault Delay to Output Disable
Oscillator Frequency, Free Run
Frequency Programming Error
FSET Input Bias Current
SYNC Logic High Input Threshold
SYNC Logic Low Input Threshold
SYNC Frequency
Maximum SYNC Pulse Width
(Logic High or Logic Low)
TG On Voltage
TG Off Voltage
TG Rise/Fall Time
BG On Voltage
BG Off Voltage
BG Rise/Fall Time
SG On Voltage
SG Off Voltage
SG Rise/Fall Time
SG to BG Enable Lag Time
TG to BG Enable Lag Time
= 12V, V
BSTREF
= 0V, V
VC
= 2V, V
TS
= 0V, V
CONDITIONS
Measured at Feedback Pin
V
Source
Sink
(Note 3)
Measured at SENSE Pin
Measured at BG Output
>50mV Overdrive
Measured at F
f
F
Positive-Going Edge
Negative-Going Edge
f
10% to 90%/90% to 10%
10% to 90%/90% to 10%
10% to 90%/90% to 10%
4V On/Off Thresholds
4V On/Off Thresholds
OSC
OSC
SET
FB
FB
= V
= Oscillator Free-Run Frequency
Charging, V
= V
500kHz (Note 3)
REF
REF
= 1.25V, C
SET
FSET
Pin
= 2V
TG
= C
BG
= C
SG
= 1000pF.
f
1.242
1.225
OSC
MIN
135
130
–10
0.5
1.2
0.8
10
20
11
11
11
80
/2
1.250
– 275
1.25
11.5
11.5
11.5
TYP
–50
150
175
250
650
150
100
1.4
3.2
1.4
1.4
0.1
0.1
0.1
72
25
12
40
50
35
35
35
1
1
A
= 25 C.
1/f
1.265
1.258
MAX
165
170
700
350
300
1.3
0.5
0.5
0.5
60
12
12
5
2
OSC
LT3781
UNITS
3
MHz
3781f
kHz
kHz
V/V
mA
mA
mV
mV
mV
nA
dB
nA
ns
ns
ns
ns
ns
ns
ns
ns
%
V
V
V
V
A
V
V
V
V
V
V
V
V
V
s