LT1508ISW View Datasheet(PDF) - Linear Technology
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LT1508ISW Datasheet PDF : 16 Pages
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LT1508
ELECTRICAL CHARACTERISTICS
VCC = 18V, RSET = 15k to GND, CSET = 1nF to GND, IAC = 100µA, ISENSE = 0V, CAOUT = 3.5V, VAOUT = 5V, OVP = VREF. No load on any
outputs, unless otherwise noted.
PARAMETER
Soft Start Current
SS1 Current (PFC)
SS2 Current (PWM)
Comparators in PWM Section
ILIM Input Current
Current Limit Comparator (CL) Threshold
GTDR2 Switching Off Threshold at VC or at SS2
VC Input Current
PWMOK Comparator Low Threshold (in Terms of VREF)
VC Pin High Voltage
GTDR2 Turn-On Blanking Time
CONDITIONS
SS1 = 2.5V
SS2 = 1V
ILIM = 0V, VC = 1.6V
VC > 2.6V
ILIM = 0V
VC = 0V
1mA into VC Pin
MIN TYP MAX
q
5
q
5
12
30
12
30
q
– 0.3 – 2
q
0.95
1.1
1.20
q
1
q – 20
– 80
q 0.57 0.63 0.70
q
6.2
6.9
7.5
180
UNITS
µA
µA
µA
V
V
µA
V
ns
The q denotes specifications which apply over the full operating
temperature range.
Note 1: Multiplier Gain Constant: K =
IM
IAC (VAOUT – 2)2
Note 2: GTDR2 (PWM) pulse is delayed by 53% duty cycle after GTDR1
(PFC) is set. See PFC/PWM Synchronization graph in the Typical
Performance Characteristics section.
TYPICAL PERFORMANCE CHARACTERISTICS
PFC Voltage Amplifier Open-Loop
Gain and Phase
100
0
80
–20
GAIN
60
–40
40
–60
20
PHASE
0
–80
–100
–20
–120
10 100 1k 10k 100k 1M 10M
FREQUENCY (Hz)
1508 G01
PFC Current Amplifier Open-Loop
Gain and Phase
100
0
80
–20
GAIN
60
–40
40
–60
20
PHASE
0
–80
–100
–20
–120
10 100 1k 10k 100k 1M 10M
FREQUENCY (Hz)
1508 G02
PFC/PWM Synchronization
PFC (GTDR1)
53%
PWM (GTDR2)
TIME
1508 G03
4
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