Datasheet

3
LT1680
Note 2: Supply current specification does not include external FET gate
charge currents. Actual supply currents will be higher and vary with
operating frequency, operating voltages and the type of external FETs used.
See Applications Information.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Error Amplifier
V
SENSE
Peak Current Limit Threshold Measured at Sense Inputs ● 170 190 mV
Average Current Limit Threshold Measured at Sense Inputs, V
CMSENSE
= 10V ● 110 120 130 mV
V
IAVG
Average Current Limit Threshold Measured at I
AVG
Pin 2.5 V
Current Sense Amplifier
A
V
Amplifier DC Gain Measured at I
AVG
Pin 15 V/V
V
OS
Amplifier Input Offset Voltage 2V < V
CMSENSE
< 60V, ● 0.1 mV
SENSE
+
– SENSE
–
= 5mV
I
BIAS
Input Bias Current Sink (V
CMSENSE
> 5V) ● 45 75 µA
Source (V
CMSENSE
= 0V) ● 700 1200 µA
Oscillator
f
O
Operating Frequency, Free Run ● 200 kHz
Frequency Programming Error f
O
≤ 200kHz, R
CT
= 16.9k, C
CT
= 1000pF ● –5 5 %
I
CT
Timing Capacitor Discharge Current LT1680C ● 2.20 2.5 2.75 mA
LT1680I
● 2.10 2.5 2.75 mA
V
SYNC
SYNC Input Threshold Rising Edge ● 0.8 2.0 V
f
SYNC
SYNC Frequency Range f
SYNC
≤ 200kHz ● f
O
1.4f
O
Output Drivers
V
GATE
Undervoltage Output Clamp 12V
IN
≤ 8.2V ● 0.4 0.7 V
Standby Mode Output Clamp V
RUN
< 0.5V ● 0.1 V
Gate Output On Voltage
● 11 11.9 12 V
Gate Output Off Voltage
● 0.4 0.7 V
t
GATER
Gate Output Rise Time ● 60 200 ns
t
GATEF
Gate Output Fall Time ● 60 140 ns
Note 1: Absolute Maximum Ratings are those values beyond which the life of
a device may be impaired.
The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at T
A
= 25°C.
12V
IN
= 12V, V
VC
= 2V, V
FB
= V
REF
= 1.25V, C
GATE
= 3000pF, unless otherwise noted.
ELECTRICAL CHARACTERISTICS