Datasheet

3
LT1533
ELECTRICAL CHARACTERISTICS
V
IN
= 5V, V
C
= 0.9V, V
FB
= V
REF
. COL A, COL B, SHDN, NFB, DUTY pins open, unless otherwise noted.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
g
m
Error Amplifier Transconductance I
C
= ±25µA 1100 1500 1900 µmho
700 2300 µmho
I
ESK
Error Amplifier Sink Current V
FB
= V
REF
+ 150mV, V
C
= 0.9V, V
SHDN
= 1V 120 200 350 µA
I
ESRC
Error Amplifier Source Current V
FB
= V
REF
– 150mV, V
C
= 0.9V, V
SHDN
= 1V 120 200 350 µA
V
CLH
Error Amplifier Clamp Voltage High Clamp, V
FB
= 1V 1.33 V
V
CLL
Error Amplifier Clamp Voltage Low Clamp, V
FB
= 1.5V 0.1 V
A
V
Error Amplifier Voltage Gain 180 250 V/V
Oscillator and Sync
f
MAX
Maximum Switch Frequency 250 kHz
f
SYNC
Synchronization Frequency Range f
OSC
= 250kHz 375 kHz
R
SYNC
SYNC Pin Input Resistance 40 k
V
FBfs
FB Pin Threshold for Frequency Shift 5% Reduction from Nominal 0.4 V
Output Switches
DC
MAX
Maximum Switch Duty Cycle DUTY Pin Open, R
VSL
= R
CSL
= 4.9k, f
OSC
= 25kHz 44 45.5 %
DUTY Pin Grounded, Forced 50% Duty Cycle 50.0 %
t
IBL
Switch Current Limit Blanking Time 200 ns
BV Output Switch Breakdown Voltage 2.7V V
IN
23V 25 30 V
R
ON
Output Switch-On Resistance I
COL A
or I
COL B
= 0.75A 0.5 0.85
I
LIM(MAX)
Maximum Current Limit Duty Cycle = 15% 1 1.25 1.8 A
Short-Circuit Current Limit Duty Cycle = 40% 0.8 A
I
IN
/I
SW
Supply Current Increase During 16 mA/A
Switch-On Time
V
DUTYTH
DUTY Pin Threshold 0.35
Slew Control
V
SLEWR
Output Voltage Slew Rising Edge Either A or B, R
VSL
, R
CSL
= 17k 11 V/µs
V
SLEWF
Output Voltage Slew Falling Edge Either A or B, R
VSL
, R
CSL
= 17k 14.5 V/µs
I
SLEWR
Output Current Slew Rising Edge Either A or B, R
VSL
, R
CSL
= 17k 1.3 A/µs
I
SLEWF
Output Current Slew Falling Edge Either A or B, R
VSL
, R
CSL
= 17k 1.3 A/µs
The denotes specifications that 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 LT1533 is designed to operate over the junction temperature
range of –40°C to 125°C, but is neither tested nor guaranteed beyond 0°C
to 100°C for C grade or –40°C to 100°C for I grade.