LT1683 Datasheet, PDF (1/24 Pages) Linear Technology – Ultralow Noise Push-Pull DC/DC Controller

FEATURES
s _{Greatly Reduced Conducted and Radiated EMI}
s _{Low Switching Harmonic Content}
s _{Independent Control of Output Switch Voltage and}
Current Slew Rates
s _{Greatly Reduced Need for External Filters}
s _{Dual N-Channel MOSFET Drivers}
s _{20kHz to 250kHz Oscillator Frequency}
s _{Easily Synchronized to External Clock}
s _{Regulates Positive and Negative Voltages}
s _{Easier Layout Than with Conventional Switchers}
U
APPLICATIO S
s _{Power Supplies for Noise Sensitive Communication}
Equipment
s _{EMI Compliant Offline Power Supplies}
s _{Precision Instrumentation Systems}
s _{Isolated Supplies for Industrial Automation}
s _{Medical Instruments}
s _{Data Acquisition Systems}
, LTC and LT are registered trademarks of Linear Technology Corporation.
LT1683
Ultralow Noise
Push-Pull DC/DC Controller
DESCRIPTIO
The LT^®1683 is a switching regulator controller designed
to lower conducted and radiated electromagnetic interfer-
ence (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 cir-
cuitry can regulate both positive and negative voltages.
The oscillator 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 APPLICATIO
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
25k 3.3k
1.5k
0.22µF 22nF
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
15
R_CSL
20
PGND
12
V_C
9
FB
SS GND NFB
13 11 10
10nF
10pF
200V
Si9422
MBRS340
10pF
200V
30pF
0.1Ω
30pF
22µH
150µF
OS-CON
OPTIONAL
B
22µH
A 5V/2A
2×100µF
POSCAP
7.50k
2.49k
A
200µV/DIV
B
20mV/DIV
1683 TA01
5V Output Noise
(Bandwidth = 100MHz)
200µV_P-P
5µs/DIV
1683 TA01a
1683f
1