LT1533_15 Datasheet, PDF (1/20 Pages) Linear Technology – Ultralow Noise 1A Switching Regulator

FEATURES
s _{Greatly Reduced Conducted and Radiated EMI}
(<100µV_P-P in Typical Application)
s _{Low Switching Harmonic Content}
s _{Independent Control of Switch Voltage and}
Current Slew Rates
s _{Two 1A Current Limited Power Switches}
s _{Regulates Positive and Negative Voltages}
s _{20kHz to 250kHz Oscillator Frequency}
s _{Easily Synchronized to External Clock}
s _{Wide Input Voltage Range: 2.7V to 23V}
s _{Low Shutdown Current: 12µA Typical}
s _{Easier Layout than with Conventional Switchers}
s _{Outputs Can Be Forced to 50% Duty Cycle for}
Unregulated Applications
U
APPLICATIONS
s _{Precision Instrumentation Systems}
s _{Isolated Supplies for Industrial Automation}
s _{Medical Instruments}
s _{Wireless Communications}
s _{Single Board Data Acquisition Systems}
, LTC and LT are registered trademarks of Linear Technology Corporation.
LT1533
Ultralow Noise
1A Switching Regulator
DESCRIPTION
The LT^®1533 is a new class of switching regulator designed
to reduce conducted and radiated electromagnetic interfer-
ence (EMI). Ultralow noise and EMI are achieved by providing
user control of the output switch slew rates. Voltage and
current slew rates can be independently programmed to
optimize switcher harmonic content versus efficiency. The
LT1533 can reduce high frequency harmonic power by as
much as 40dB with only minor losses in efficiency.
The LT1533 utilizes a dual output switch current mode
architecture optimized for low noise topologies. The IC
includes two 1A power switches along with all necessary
oscillator, control and protection circuitry. Unique error amp
circuitry can regulate both positive and negative voltages.
The internal oscillator may be synchronized to an external
clock for more accurate placement of switching harmonics.
Protection features include cycle by cycle current limit pro-
tection, undervoltage lockout and thermal shutdown.
Low minimum supply voltage and low supply current during
shutdown make the LT1533 well suited for portable applica-
tions. The part may also be forced into a 50% duty cycle mode
for unregulated applications. The LT1533 is available in the
16-pin narrow SO package.
TYPICAL APPLICATION
Low Noise 5V to 12V Forward Push-Pull DC/DC Converter
+
0.015µF
5V
14
33µF ₁₁
V_IN
2
SHDN
COL A
820pF
16.9k
3
DUTY
15
4
SYNC
COL B
5 _CT
16
PGND
LT1533
13
6 _RT
R_VSL
12
R_CSL
15k ₁₀
7
V_{C GND}
FB
NFB
1000pF 9
8
T1 ^1N4148
L1
300µH
L2
B ^33µH A
Note 1
1N4148 + ^C1 +
47µF
16V
15k
15k
21.5k, 1%
1533 TA01
2.49k
1%
C1: SANYO OS-CON
C2: AVX TPS TANTALUM
L1: COILTRONICS CTX300-2
L2: COILCRAFT DT1608C-333
T1: COILTRONICS CTX02-13834
NOTE 1: 25nH TRACE INDUCTANCE
OR COILCRAFT B07T
12V
150mA
12V Output Noise (BW = 100MHz)
C2
33µF
20V
A
100µV/DIV
< 100µV_P-P
B
2mV/DIV
2µs/DIV
1533 TA02
1