Datasheet

LT1170/LT1171/LT1172
4
117012fg
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature 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.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
REF
Reference Voltage Measured at Feedback Pin
V
C
= 0.8V l
1.224
1.214
1.244
1.244
1.264
1.274
V
V
I
B
Feedback Input Current V
FB
= V
REF
l
350 750
1100
nA
nA
g
m
Error Amplifier Transconductance ∆I
C
= ±25µA
l
3000
2400
4400 6000
7000
µmho
µmho
Error Amplifier Source or Sink Current V
C
= 1.5V
l
150
120
200 350
400
µA
µA
Error Amplifier Clamp Voltage Hi Clamp, V
FB
= 1V
Lo Clamp, V
FB
= 1.5V
1.80
0.25 0.38
2.30
0.52
V
V
Reference Voltage Line Regulation 3V ≤ V
IN
≤ V
MAX
V
C
= 0.8V
l 0.03 %/V
A
V
Error Amplifier Voltage Gain 0.9V ≤ V
C
≤ 1.4V 500 800 V/V
Minimum Input Voltage (Note 5)
l
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
l
0.8
0.6
0.9 1.08
1.25
V
V
Normal/Flyback Threshold on Feedback Pin 0.4 0.45 0.54 V
V
FB
Flyback Reference Voltage (Note 5) I
FB
= 50µA
l
15.0
14.0
16.3 17.6
18.0
V
V
Change in Flyback Reference Voltage 0.05 ≤ I
FB
≤ 1mA 4.5 6.8 9 V
Flyback Reference Voltage Line Regulation
(Note 5)
I
FB
= 50µA
7V ≤ V
IN
≤ V
MAX
0.01 0.03 %/V
Flyback Amplifier Transconductance (g
m
)∆I
C
= ±10µA 150 300 650 µmho
Flyback Amplifier Source and Sink Current V
C
= 0.6V Source
I
FB
= 50µA Sink
l
l
15
25
32
40
70
70
mA
mA
BV Output Switch Breakdown Voltage 3V ≤ V
IN
≤ V
MAX
, LT1170/LT1171/LT1172
I
SW
= 1.5mA LT1170HV/LT1171HV/LT1172HV
LT1172S8
l
l
l
65
75
60
90
90
80
V
V
V
V
SAT
Output Switch “On” Resistance (Note 3) LT1170
LT1171
LT1172
l
l
l
0.15
0.30
0.60
0.24
0.50
1.00



Control Voltage to Switch Current
Transconductance
LT1170
LT1171
LT1172
8
4
2
A/V
A/V
A/V
I
LIM
Switch Current Limit (LT1170) Duty Cycle = 50% T
J
≥ 25°C
Duty Cycle = 50% T
J
< 25°C
Duty Cycle = 80% (Note 4)
l
l
l
5
5
4
10
11
10
A
A
A
(LT1171) Duty Cycle = 50% T
J
≥ 25°C
Duty Cycle = 50% T
J
< 25°C
Duty Cycle = 80% (Note 4)
l
l
l
2.5
2.5
2.0
5.0
5.5
5.0
A
A
A
(LT1172) Duty Cycle = 50% T
J
≥ 25°C
Duty Cycle = 50% T
J
< 25°C
Duty Cycle = 80% (Note 4)
l
l
l
1.25
1.25
1.00
3.0
3.5
2.5
A
A
A
∆I
IN
∆I
SW
Supply Current Increase During Switch
On-Time
25 35 mA/A
f Switching Frequency
l
88
85
100 112
115
kHz
kHz