Datasheet

LTC1772B
3
1772bfa
ELECTRICAL CHARACTERISTICS
The l denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at T
A
= 25°C. V
IN
= 4.2V unless otherwise specifi ed. (Note 2)
PARAMETER CONDITIONS MIN TYP MAX UNITS
V
FB
Input Current (Note 5) 10 50 nA
Overvoltage Protect Threshold Measured at V
FB
0.820 0.860 0.895 V
Overvoltage Protect Hysteresis 20 mV
Oscillator Frequency V
FB
= 0.8V
V
FB
= 0V
500 550
120
650 kHz
kHz
Gate Drive Rise Time C
LOAD
= 3000pF 40 ns
Gate Drive Fall Time C
LOAD
= 3000pF 40 ns
Peak Current Sense Voltage (Note 6) 105 mV
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: The LTC1772BE is guaranteed to meet specifi cations from 0°C to
85°C. Specifi cations over the –40°C to 85°C operating temperature range
are assured by design, characterization and correlation with statistical
process controls. The LTC1772BI is guaranteed to meet specifi cations over
the full –40°C to 85°C operating temperature range.
Note 3: T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
according to the following formula:
T
J
= T
A
+ (P
D
• θ
JA
°C/W)
Note 4: Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency.
Note 5: The LTC1772B is tested in a feedback loop that servos V
FB
to the
output of the error amplifi er.
Note 6: Peak current sense voltage is reduced dependent on duty cycle to
a percentage of value as given in Figure 2.