Datasheet

3
LT1072
1072fc
SYMBOL PARAMETER CONDITlONS MIN TYP MAX UNITS
V
REF
Reference Voltage Measured at Feedback Pin 1.224 1.244 1.264 V
V
C
= 0.8V ● 1.214 1.244 1.274 V
I
B
Feedback Input Current V
FB
= V
REF
350 750 nA
● 1100 nA
gm Error Amplifier ∆I
C
= ±25µA 3000 4400 6000 µmho
Transconductance
● 2400 7000 µmho
Error Amplifier Source or V
C
= 1.5V 150 200 350 µA
Sink Current
● 120 400 µA
Error Amplifier Clamp Hi Clamp, V
FB
= 1V 1.8 2.3 V
Voltage Lo Clamp, V
FB
= 1.5V 0.25 0.38 0.52 V
Reference Voltage Line 3V ≤ V
IN
≤ V
MAX
● 0.03 %/V
Regulation V
C
= 0.8V %/V
A
V
Error Amplifier Voltage Gain 0.9V ≤ V
C
≤ 1.4V 500 800 V/V
Minimum Input Voltage ● 2.6 3.0 V
I
Q
Supply Current 3V ≤ V
IN
≤ V
MAX
, V
C
= 0.6V 6 9 mA
Control Pin Threshold Duty Cycle = 0 0.8 0.9 1.08 V
● 0.6 1.25 V
Normal/Flyback Threshold on Feedback Pin 0.4 0.45 0.54 V
V
FB
Flyback Reference Voltage l
FB
= 50µA1516.3 17.6 V
● 14 18 V
Change in Flyback Reference Voltage 0.05 ≤ I
FB
≤ 1mA 4.5 6.8 8.5 V
Flyback Reference Voltage l
FB
= 50µA 0.01 0.03 %/V
Line Regulation 3V ≤ V
IN
≤ V
MAX
(Note 4) %/V
Flyback Amplifier Transconductance (gm) ∆I
C
= ±10µA 150 300 650 µmho
Flyback Amplifier Source V
C
= 0.6V Source ● 15 32 70 µA
and Sink Current I
FB
= 50µA Sink ● 25 40 70 µA
BV Output Switch Breakdown 3V ≤ V
IN
≤ V
MAX
LT1072 ● 65 90 V
Voltage I
SW
= 1.5mA LT1072HV ● 75 90 V
LT1072S8
● 60 80 V
V
SAT
Output Switch ON Resistance (Note 2) I
SW
= 1.25A ● 0.6 1 Ω
Control Voltage to Switch Current Transconductance 2 A/V
I
LIM
Switch Current Limit Duty Cycle = 50% T
J
≥ 25°C ● 1.25 3 A
Duty Cycle = 50% T
J
< 25°C ● 1.25 3.5 A
Duty Cycle = 80% (Note 3) ● 1 2.5 A
∆I
IN
Supply Current Increase 25 35 mA/A
∆I
SW
During Switch ON Time
f Switching Frequency 35 40 45 kHz
● 33 47 kHz
DC (max) Maximum Switch Duty Cycle 90 92 97 %
Flyback Sense Delay Time 1.5 µs
Shutdown Mode 3V ≤ V
IN
≤ V
MAX
100 250 µA
Supply Current V
C
= 0.05V
Shutdown Mode 3V ≤ V
IN
≤ V
MAX
100 150 250 mV
Threshold Voltage ● 50 300 mV
The ● denotes specifications which apply over the full operating
temperature range. Unless otherwise specified, V
IN
= 15V, V
C
= 0.5V, V
FB
= V
REF
, output pin open.
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: Measured with V
C
in hi clamp, V
FB
= 0.8V.
Note 3: For duty cycles (DC) between 50% and 80%, minimum
guaranteed switch current is given by I
LIM
= 0.833 (2 – DC).
Note 4: V
MAX
= 55V for LT1072HV to avoid switch breakdown.
ELECTRICAL CHARACTERISTICS