LT1683_15 Datasheet, PDF (1/26 Pages) Linear Technology – Slew Rate Controlled Ultralow Noise Push-Pull DC/DC Controller

LT1683
Slew Rate Controlled
Ultralow Noise Push-Pull DC/DC Controller
FEATURES
DESCRIPTION
n _{Greatly Reduced Conducted and Radiated EMI}
n _{Low Switching Harmonic Content}
n _{Independent Control of Output Switch Voltage and}
Current Slew Rates
n _{Greatly Reduced Need for External Filters}
n _{Dual N-Channel MOSFET Drivers}
n _{20kHz to 250kHz Oscillator Frequency}
n _{Easily Synchronized to External Clock}
n _{Regulates Positive and Negative Voltages}
n _{Easier Layout Than with Conventional Switchers}
APPLICATIONS
n _{Power Supplies for Noise Sensitive Communication}
Equipment
n _{EMI Compliant Offline Power Supplies}
n _{Precision Instrumentation Systems}
n _{Isolated Supplies for Industrial Automation}
n _{Medical Instruments}
n _{Data Acquisition Systems}
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
DirectSense is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
The LT^®1683 is a switching regulator controller designed to
lower conducted and radiated electromagnetic interference
(EMI). Ultralow noise and EMI are achieved by controlling
the voltage and current slew rates of external N-channel
MOSFET switches. Current and voltage slew rates can
be independently set to optimize harmonic content of
the switching waveforms vs efficiency. The LT1683 can
reduce high frequency harmonic power by as much as
40dB with only minor losses in efficiency.
The LT1683 utilizes a dual output (push-pull) current
mode architecture optimized for low noise topologies.
The IC includes gate drivers and all necessary oscillator,
control and protection circuitry. Unique error amp circuitry
can regulate both positive and negative voltages. The oscil-
lator may be synchronized to an external clock for more
accurate placement of switching harmonics.
Protection features include gate drive lockout for low V_IN,
opposite gate lockout, soft-start, output current limit,
short-circuit current limiting, gate drive overvoltage clamp
and input supply undervoltage lockout.
TYPICAL APPLICATION
Ultralow Noise 48V to 5V DC/DC Converter
51k
1N4148
510Ω
0.5W
FZT853
10µF
20V
2N3904
8.2V
48V
39µF
63V
MIDCOM 31244
MBR0530
MBRS340
11V
68µF
20V
17 3
23.2k
976Ω
1.2nF
16.9k
25k 3.3k
V_IN GCL
5pF
14
SHDN
5
V5
6
SYNC
2
CAP A
1
GATE A
5pF
7
C_T
18
CAP B
8
R_T
LT1683
19
GATE B
16
R_VSL
4 Si9422
CS
25k 3.3k
1.5k
15
R_CSL
12
V_C
0.22µF 22nF
SS
20
PGND
9
FB
GND NFB
13 11 10
10nF
10pF
200V
Si9422
MBRS340
10pF
200V
30pF
0.1Ω
30pF
22µH
150µF
OS-CON
OPTIONAL
B
22µH
2×100µF
POSCAP
7.50k
2.49k
A 5V/2A
A
200µV/DIV
B
20mV/DIV
1683 TA01
5V Output Noise
(Bandwidth = 100MHz)
200µV_P-P
5µs/DIV
1683 TA01a
1683fd
1