LT1103_15 Datasheet, PDF (5/32 Pages) Linear Technology – Offline Switching Regulator

LT1103/LT1105
ELECTRICAL CHARACTERISTICS
V_IN = 20V, V_C = 0.85V, OVLO = 0V, V_SW Open, T_A = 25°C, unless otherwise noted.
SYMBOL
PARAMETER
Switch Output Low Level
(LT1105)
Rise Time (LT1105)
Fall Time (LT1105)
I_LIM Threshold Voltage (LT1105)
Low Switch Drive Lockout
Threshold
High Switch Drive Lockout
Threshold
CONDITONS
I_SW = 200mA
I_SW = 750mA
C_L = 1000pF
C_L = 1000pF
Duty Cycle = 25% (Note 5)
Measured at V_SW (LT1103)
Measured at 15V Gate Bias Reference (LT1105)
Measured at V_SW (LT1103)
Measured at 15V Gate Bias Reference (LT1105)
MIN TYP MAX UNIT
q
0.25 0.50
V
q
0.75 1.50
V
50
ns
20
ns
q 300 375 450
mV
q 9.0 9.5 10.5
V
q 17.0 18.5 20.0
V
The q denotes specifications which apply over the full operating
temperature range.
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: The OVLO pin is clamped with a 5.5V Zener and can sink a
maximum input current of 1mA.
Note 3: FB input bias current changes as a function of the V_C pin voltage.
Rate of change of FB input bias current is 11µA/V of change on V_C. By
including a resistor in series with the FB pin, load regulation can be set
to zero.
Note 4: Current limit on V_SW is constant for DC < 35% and decreases for
DC > 35% due to internal slope compensation circuity. The LT1103 switch
current limit is given by I_LIM = 1.76 (1.536 – DC) above 35% duty cycle.
Note 5: The current limit threshold voltage is constant for DC < 35% and
decreases for DC > 35% due to internal slope compensation circuitry. The
LT1105 switch current limit threshold voltage is given by V_LIM = 0.225
(1.7 – DC) above 35% duty cycle.
TYPICAL PERFORMANCE CHARACTERISTICS
Supply Current vs Input Voltage
25
25°C
20
15
10
5
I_SHUT
I_START
0
0 5 10 15 20 25 30
INPUT VOLTAGE (V)
LT1103 G01
Start-Up Supply Current vs
Input Voltage
500
450
400
350
300
125°C
25°C
250
200
150
–55°C
100
50
0
0
3
6
9
12
15
INPUT VOLTAGE (V)
LT1103 G02
Quiescent Supply Current vs
Input Voltage
22
21
20
125°C
19
25°C
18
17
16
–55°C
15
14
13
12
0 5 10 15 20 25 30 35 40
INPUT VOLTAGE (V)
LT1103 G03
5