LT1683
1
1683fd
TYPICAL APPLICATION
DESCRIPTION
Slew Rate Controlled
Ultralow Noise Push-Pull DC/DC Controller
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.
Ultralow Noise 48V to 5V DC/DC Converter
FEATURES
APPLICATIONS
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
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
A
B
MBRS340
MIDCOM 31244
22µH
150µF
OS-CON
MBRS340
MBR0530
22µH
OPTIONAL
2×100µF
POSCAP
5V/2A
3
10
1683 TA01
1113
SHDN
CAP A
NFB
LT1683
GND
V
IN
17
14 2
GCL
SS
V5
SYNC
GATE A
5
1
C
T
CAP B
6
18
R
T
GATE B
7
19
8
R
CSL
16
V
C
15
12
R
VSL
CS
4
PGND
20
FB
9
5pF
5pF
Si9422
Si9422
0.1Ω
976Ω
23.2k
10nF
1.5k
3.3k
25k
25k
3.3k
16.9k
1.2nF
39µF
63V
48V
68µF
20V
11V
8.2V
51k
510Ω
0.5W
2N3904
1N4148
10µF
20V
30pF
22nF0.22µF
7.50k
2.49k
FZT853
10pF
200V
30pF
10pF
200V
5V Output Noise
(Bandwidth = 100MHz)
A
200µV/DIV
B
20mV/DIV
200µV
P-P
5µs/DIV 1683 TA01a
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.