Datasheet

3
LT1170/LT1171/LT1172
SYMBOL PARAMETER CONDITIONS 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
g
m
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 1.80 2.30 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
A
V
Error Amplifier Voltage Gain 0.9V ≤ V
C
≤ 1.4V 500 800 V/V
Minimum Input Voltage (Note 5) ● 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 0.4 0.45 0.54 V
on Feedback Pin
V
FB
Flyback Reference Voltage I
FB
= 50µA 15.0 16.3 17.6 V
(Note 5) ● 14.0 18.0 V
Change in Flyback Reference 0.05 ≤ I
FB
≤ 1mA 4.5 6.8 9 V
Voltage
Flyback Reference Voltage I
FB
= 50µA 0.01 0.03 %/V
Line Regulation (Note 5) 7V ≤ V
IN
≤ V
MAX
Flyback Amplifier ∆I
C
= ±10µA 150 300 650 µmho
Transconductance (g
m
)
Flyback Amplifier Source V
C
= 0.6V Source ● 15 32 70 µA
and Sink Current I
FB
= 50µASink ● 25 40 70 µA
BV Output Switch Breakdown 3V ≤ V
IN
≤ V
MAX
, LT1170/LT1171/LT1172 ● 65 90 V
Voltage I
SW
= 1.5mA LT1170HV/LT1171HV/LT1172HV ● 75 90 V
LT1172S8 ● 60 80 V
V
SAT
Output Switch LT1170 ● 0.15 0.24 Ω
“On” Resistance (Note 3) LT1171
● 0.30 0.50 Ω
LT1172 ● 0.60 1.00 Ω
Control Voltage to Switch LT1170 8 A/V
Current Transconductance LT1171 4 A/V
LT1172 2 A/V
I
LIM
Switch Current Limit (LT1170) Duty Cycle = 50% T
J
≥ 25°C ● 510A
Duty Cycle = 50% T
J
< 25°C ● 511A
Duty Cycle = 80% (Note 4) ● 410A
(LT1171) Duty Cycle = 50% T
J
≥ 25°C ● 2.5 5.0 A
Duty Cycle = 50% T
J
< 25°C ● 2.5 5.5 A
Duty Cycle = 80% (Note 4) ● 2.0 5.0 A
(LT1172) Duty Cycle = 50% T
J
≥ 25°C ● 1.25 3.0 A
Duty Cycle = 50% T
J
< 25°C ● 1.25 3.5 A
Duty Cycle = 80% (Note 4) ● 1.00 2.5 A
The ● denotes the specifications which apply over the full operating tem-
perature range, otherwise specifications are at T
A
= 25°C. V
IN
= 15V, V
C
= 0.5V, V
FB
= V
REF
, output pin open, unless otherwise noted.
ELECTRICAL CHARACTERISTICS