Datasheet

3
LT1681
1681f
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
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
5V External Reference
V
5VREF
5V Reference Voltage 0 ≤ (I
5VREF
– I
VC
) < 20mA 4.85 5 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
Error Amp
V
FB
Error Amplifier Reference Voltage Measured at Feedback Pin 1.242 1.250 1.258 V
● 1.225 1.265 V
I
FB
Feedback Input Current V
FB
= V
REF
–50 nA
A
V
Error Amplifier Voltage Gain 72 dB
I
VC
Error Amplifier Current Limit Source ● 10 25 mA
Sink
● 0.5 1 mA
V
VC
Zero Current Output Voltage 1.4 V
Maximum Output Voltage 3.2 V
GBW Gain Bandwidth Product (Note 3) 1 MHz
Current Sense and Blanking
A
V
Amplifier DC Gain 12 V/V
I
SENSE
Input Bias Current –275 µA
V
SENSE
Current Limit Threshold Measured at SENSE Pin 135 150 165 mV
● 130 170 mV
t
D
Current Sense to Switch Delay 175 ns
V
BLKSENS
Blanking Input Threshold ● 4.5 5 5.5 V
I
BLKSENS
Blanking Input Bias Current –2 µA
t
MIN
Switch Minimum On Time V
BLKSENS
= V
BG
, Measured at BG Output 250 ns
I
MAX
Sense
I
IMAX
Input Bias Current –250 µA
V
IMAX
I
MAX
Threshold (Rising Edge) Measured at I
MAX
Input ● 320 360 400 mV
I
MAX
Threshold Hysteresis Measured at I
MAX
Input 140 mV
t
P
I
MAX
Output Switch Disable Delay Measured at BG Output 130 ns
THERM and OVLO Fault Detectors
V
THERM
/ Threshold (Rising Edge) ● 1.2 1.25 1.3 V
V
OVLO
Threshold Hysteresis ● 20 40 60 mV
t
P
Fault Delay to Output Disable 50mV Overdrive 650 ns
Oscillator and Synchronization Decoder
f
OSC
Oscillator Frequency, Free Run Measured at FSET Pin 700 kHz
Frequency Programming Error, Free Run f
OSC
≤ 500kHz (Note 3) ● –10 5 %
I
FSET
FSET Input Bias Current FSET Charging, V
FSET
= 2V 50 nA
V
SYNC
SYNC Logic High Input Threshold Positive-Going Edge ● 1.4 2 V
SYNC Logic Low Input Threshold Negative-Going Edge
● 0.8 1.4 V
f
SYNC
SYNC Frequency ● f
OSC
/2 350 kHz
t
H, L
Maximum SYNC Pulse Width f
OSC
= Oscillator Free-Run Frequency 1/f
OSC
s
(Logic High or Logic Low)