DC/DC Controller. LT1738 Datasheet

LT1738 Controller. Datasheet pdf. Equivalent

Part LT1738
Description Slew Rate Controlled Ultralow Noise DC/DC Controller
Feature U U LT1738 Slew Rate Controlled Ultralow Noise DC/DC Controller FEATURES s Greatly Reduced Conduct.
Manufacture Linear
Datasheet
Download LT1738 Datasheet



LT1738
LT1738
Slew Rate Controlled
Ultralow Noise 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 Single N-Channel MOSFET Driver
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
DESCRIPTIO
The LT®1738 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 an exter-
nal N-channel MOSFET switch. Current and voltage slew
rates can be independently set to optimize harmonic
content of the switching waveforms vs efficiency. The
LT1738 can reduce high frequency harmonic power by as
much as 40dB with only minor losses in efficiency.
The LT1738 utilizes a current mode architecture opti-
mized for single switch topologies such as boost, flyback
and Cuk. The IC includes gate drive and 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 switch-
ing harmonics.
Protection features include gate drive lockout for low VIN,
soft-start, output current limit, short-circuit current limit-
ing, gate drive overvoltage clamp and input supply
undervoltage lockout.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
Ultralow Noise 5V to 12V Converter
5V
VIN
+
100µF
1.3nF
16.9k
25k 3.3k
25k 3.3k
22nF
0.22µF
1.5k
22µH
P3
17 3
VIN GCL 5pF
14
SHDN
5
V5
6
SYNC
2
CAP
7
CT
1
GATE
8
RT
LT1738
16
RVSL
4
CS
15
RCSL
20
PGND
12
VC
9
FB
SS GND NFB
13 11 10
10nF
MBRD620
B
+
4 × 150µF
OSCON
10µH
150µF +
OSCON
OPTIONAL
A 12V
1A
POINT A
ON SCHEMATIC
500µV/DIV
Si9426
25m
21.5k
POINT B
ON SCHEMATIC
50mV/DIV
2.5k
1738 TA01
12V Output Noise
(Bandwidth = 100MHz)
400µVP-P
5µs/DIV
1738 TA01a
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LT1738
LT1738
ABSOLUTE AXI U RATI GS
(Note 1)
Supply Voltage (VIN) ................................................ 20V
Gate Drive Current ..................................... Internal Limit
V5 Current ................................................. Internal Limit
SHDN Pin Voltage .................................................... 20V
Feedback Pin Voltage (Trans. 10ms) ...................... ±10V
Feedback Pin Current ............................................ 10mA
Negative Feedback Pin Voltage (Trans. 10ms) ........ ±10V
CS Pin .......................................................................... 5V
GCL Pin ..................................................................... 16V
SS Pin .......................................................................... 3V
Operating Junction Temperature Range
(Note 3) ............................................ – 40°C to 125°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
UW U
PACKAGE/ORDER I FOR ATIO
GATE 1
CAP 2
GCL 3
CS 4
V5 5
SYNC 6
CT 7
RT 8
FB 9
NFB 10
TOP VIEW
20 PGND
19 NC
18 NC
17 VIN
16 RVSL
15 RCSL
14 SHDN
13 SS
12 VC
11 GND
ORDER PART
NUMBER
LT1738EG
LT1738IG
G PACKAGE
20-LEAD PLASTIC SSOP
TJMAX = 150°C, θJA = 110°C/ W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS The q denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 12V, VC = 0.9V, VFB = VREF, RVSL, RCSL = 16.9k, RT = 16.9k and
other pins open unless otherwise noted.
SYMBOL PARAMETER
Error Amplifiers
VREF
IFB
FBREG
VNFR
Reference Voltage
Feedback Input Current
Reference Voltage Line Regulation
Negative Feedback Reference Voltage
INFR
NFBREG
gm
Negative Feedback Input Current
Negative Feedback Reference Voltage Line Regulation
Error Amplifier Transconductance
CONDITIONS
Measured at Feedback Pin
VFB = VREF
2.7V VIN 20V
Measured at Negative Feedback Pin
with Feedback Pin Open
VNFB = VNFR
2.7V VIN 20V
IC = ±50µA
IESK
IESRC
VCLH
VCLL
AV
FBOV
ISS
Error Amp Sink Current
Error Amp Source Current
Error Amp Clamp Voltage
Error Amp Clamp Voltage
Error Amplifier Voltage Gain
FB Overvoltage Shutdown
Soft-Start Charge Current
VFB = VREF + 150mV, VC = 0.9V
VFB = VREF – 150mV, VC = 0.9V
High Clamp, VFB = 1V
Low Clamp, VFB = 1.5V
Outputs Drivers Disabled
VSS = 1V
MIN TYP MAX UNITS
q 1.235
q
q
q –2.56
1.250
250
0.012
– 2.50
1.265
1000
0.03
– 2.45
V
nA
%/V
V
– 37
q
1100
q 700
q 120
q 120
180
– 25
0.009
1500
200
200
1.27
0.12
250
1.47
9.0
0.03
2200
2500
350
350
12
µA
%/V
µmho
µmho
µA
µA
V
V
V/V
V
µA
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