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Linear Technology Electronic Components Datasheet

LTC3718 Datasheet

Low Input Voltage DC/DC Controller

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LTC3718 pdf
LTC3718
www.DataSheet4U.com
Low Input Voltage
DC/DC Controller for
DDR/QDR Memory Termination
FEATURES
s Very Low VIN(MIN): 1.5V
s Ultrafast Transient Response
s True Current Mode Control
s 5V Drive for N-Channel MOSFETs Eliminates
Auxillary 5V Supply
s No Sense Resistor Required
s Uses Standard 5V Logic-Level N-Channel MOSFETs
s VOUT(MIN): 0.4V
s VOUT Tracks 1/2 VIN or External VREF
s Symmetrical Source and Sink Output Current Limit
s Adjustable Switching Frequency
s tON(MIN) <100ns
s Power Good Output Voltage Monitor
s Programmable Soft-Start
s Output Overvoltage Protection
s Optional Short-Circuit Shutdown Timer
s Small 24-Lead SSOP Package
U
APPLICATIO S
s Bus Termination: DDR/QDR Memory, SSTL, HSTL, ...
s Servers, RAID Systems
s Distributed Power Systems
s Synchronous Buck with General Purpose Boost
DESCRIPTIO
The LTC®3718 is a high current, high efficiency synchro-
nous switching regulator controller for DDR and QDRTM
memory termination. It operates from an input as low as
1.5V and provides a regulated output voltage equal to
(0.5)VIN. The controller uses a valley current control
architecture to enable high frequency operation with very
low on-times without requiring a sense resistor. Operating
frequency is selected by an external resistor and is com-
pensated for variations in VIN and VOUT. The LTC3718 uses
a pair of standard 5V logic level N-channel external
MOSFETs, eliminating the need for expensive P-channel
or low threshold devices.
Forced continuous operation reduces noise and RF inter-
ference. Fault protection is provided by internal foldback
current limiting, an output overvoltage comparator and an
optional short-circuit timer. Soft-start capability for sup-
ply sequencing can be accomplished using an external
timing capacitor. OPTI-LOOP® compensation allows the
transient response to be optimized over a wide range of
loads and output capacitors.
, LTC and LT are registered trademarks of Linear Technology Corporation.
OPTI-LOOP is a registered trademark of Linear Technology Corporation. No RSENSE is a
trademark of Linear Technology Corporation. QDR RAMs and Quad Data Rate RAMs comprise a
new family of products developed by Cypress Semiconductor, IDT and Micron Technology, Inc.
TYPICAL APPLICATIO
RON
237k
VOUT
CSS
0.1µF
C1 820pF X7R RC 4.75k
RF1 12.1k
SHDN
BOOST
VREF
TG
LTC3718
ION SW1
VFB1 SENSE+
PGOOD PGND1
SENSE
RUN/SS
ITH
SGND1
BG
INTVCC
VIN1
VIN2
SGND2 PGND2
VFB2
SW2
RF2 37.4k
DB
CMDSH-3
CB
0.33µF
M1
Si7440DP
CIN1
22µF
×2
D1
B340A
VIN
2.5V
L1 0.8µH
M2
Si7440DP
+
D2
B340A
COUT
470µF
×2
VOUT
1.25V
±10A
CIN2
4.7µF
L2
4.7µH
CVCC1
10µF
D3
MBR0520
VIN
COUT: SANYO POSCAP 4TPB470M
L1: SUMIDA CEP125-0R8MC
L2: PANASONIC ELJPC4R7MF
3718 TA01
Figure 1. High Efficiency Bus Termination Supply without Auxiliary 5V Supply
Efficiency vs Load Current
100
90
VIN = 2.5V
VOUT = 1.25V
80
70
60
50
40
30
20
10
0
0.01
FIGURE 1 CIRCUIT
0.1 1
10
LOAD CURRENT (A)
100
3718 G05/TA01a
3718fa
1


Linear Technology Electronic Components Datasheet

LTC3718 Datasheet

Low Input Voltage DC/DC Controller

No Preview Available !

LTC3718 pdf
LTC3718
ABSOLUTE AXI Uwww.DataSheet4U.com RATI GS
(Note 1)
Input Supply Voltage (VIN2) .......................10V to – 0.3V
Boosted Topside Driver Supply Voltage
(BOOST) ............................................... 42V to – 0.3V
VIN1, ION, SW1 Voltage ............................. 36V to – 0.3V
RUN/SS, PGOOD Voltages ......................... 7V to – 0.3V
VON, VREF, VRNG Voltages .......(INTVCC + 0.3V) to – 0.3V
ITH, VFB1 Voltages .................................... 2.7V to – 0.3V
SW2 Voltage ............................................. 36V to – 0.4V
VFB2 Voltage ................................................. VIN2 + 0.3V
SHDN Voltage ......................................................... 10V
TG, BG, INTVCC Peak Currents .................................. 2A
TG, BG, INTVCC RMS Currents ............................ 50mA
Operating Ambient Temperature
Range (Note 4) ................................... – 40°C to 85°C
Junction Temperature (Note 2) ............................ 125°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
UW U
PACKAGE/ORDER I FOR ATIO
TOP VIEW
RUN/SS 1
VON 2
PGOOD 3
VRNG
ITH
SGND1
4
5
6
ION 7
VFB1 8
VREF 9
SHDN 10
SGND2 11
VFB2 12
24 BOOST
23 TG
22 SW1
21 SENSE+
20 SENSE
19 PGND1
18 BG
17 INTVCC
16 VIN1
15 VIN2
14 PGND2
13 SW2
G PACKAGE
24-LEAD PLASTIC SSOP
TJMAX = 125°C, θJA = 130°C/ W
ORDER PART
NUMBER
LTC3718EG
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS The q denotes specifications which apply over the full operating
temperature range, otherwise specifications are TA = 25°C. VIN1 = 15V, VIN2 = 1.5V unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN TYP MAX
Buck Regulator
IQ(VIN1)
VFB1
VFB1(LINE)
VFB1(LOAD)
gm(EA)
tON
tON(MIN)
tOFF(MIN)
VSENSE(MAX)
VSENSE(MIN)
VFB1(OV)
VFB1(UV)
VRUN/SS(ON)
VRUN/SS(LE)
Input DC Supply Current (VIN1)
Normal
Shutdown Supply Current
Feedback Voltage Accuracy
Feedback Voltage Line Regulation
Feedback Voltage Load Regulation
Error Amplifier Transconductance
On-Time
Minimum On-Time
Minimum Off-Time
Maximum Current Sense Threshold
VPGND – VSW1 (Source)
Minimum Current Sense Threshold
VPGND – VSW1 (Sink)
Output Overvoltage Fault Threshold
Output Undervoltage Fault Threshold
RUN Pin Start Threshold
RUN Pin Latchoff Enable
VRUN/SS = 0V
ITH = 1.2V (Note 3)
VIN1 = 4V to 36V, ITH = 1.2V (Note 3)
ITH = 0.5V to 1.9V (Note 3)
ITH = 1.2V (Note 3)
ION = 60µA, VON = 1.5V
ION = 30µA, VON = 1.5V
ION = 180µA
VRNG = 1V, VFB1 = VREF/2 – 50mV
VRNG = 0V, VFB1 = VREF/2 – 50mV
VRNG = INTVCC, VFB1 = VREF/2 – 50mV
VRNG = 1V, VFB1 = VREF/2 + 50mV
VRNG = 0V, VFB1 = VREF/2 + 50mV
VRNG = INTVCC, VFB1 = VREF/2 + 50mV
RUN/SS Pin Rising
q – 0.65
q
0.93
200
400
q 108
q 76
q 148
– 140
– 97
– 200
8
q 0.8
1000
15
0.1
0.002
– 0.05
1.13
250
500
50
300
135
95
185
– 165
– 115
– 235
10
– 25
1.5
4
2000
30
0.65
– 0.3
1.33
300
600
100
400
162
114
222
– 190
– 133
– 270
12
2
4.5
2
UNITS
µA
µA
%
%/V
%
mS
ns
ns
ns
ns
mV
mV
mV
mV
mV
mV
%
%
V
V
3718fa


Part Number LTC3718
Description Low Input Voltage DC/DC Controller
Maker Linear Technology
Total Page 20 Pages
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