LTC3720EGN Linear Technology, LTC3720EGN Datasheet

IC STP-DN CNTRLR SNGL-PHS 28SSOP

LTC3720EGN

Manufacturer Part Number
LTC3720EGN
Description
IC STP-DN CNTRLR SNGL-PHS 28SSOP
Manufacturer
Linear Technology
Datasheet

Specifications of LTC3720EGN

Applications
Controller, Intel Pentium®
Voltage - Input
4 ~ 36 V
Number Of Outputs
1
Voltage - Output
1.05 ~ 1.83 V
Operating Temperature
-40°C ~ 85°C
Mounting Type
Surface Mount
Package / Case
28-SSOP
Lead Free Status / RoHS Status
Contains lead / RoHS non-compliant

Available stocks

Company
Part Number
Manufacturer
Quantity
Price
Part Number:
LTC3720EGN
Manufacturer:
LT/凌特
Quantity:
20 000
FEATURES
TYPICAL APPLICATIO
APPLICATIO S
5-Bit Programmable Output Voltage:
1.05V to 1.825V (VRM8.5)
No Sense Resistor Required
2% to 87% Duty Cycle at 200kHz
t
Supports Active Voltage Positioning
True Current Mode Control
Stable with Ceramic C
Dual N-Channel MOSFET Synchronous Drive
Power Good Output Voltage Monitor
Wide V
Adjustable Current Limit
Adjustable Switching Frequency
Forced Continuous Control Pin
Programmable Soft-Start
Output Overvoltage Protection
Optional Short-Circuit Shutdown Timer
Micropower Shutdown: I
Available in 28-Lead Narrow SSOP Package
Power Supplies for Pentium
Notebook Computers and Servers
ON(MIN)
1% 0.8V Reference
470pF
5-BIT VID
IN
0.1 F
20k
Range: 4V to 36V
100ns
PGOOD
RUN/SS
I
SGND
VID4
VID3
VID2
VID1
VID0
TH
Figure 1. High Efficiency Step-Down Converter
LTC3720
U
V
SENSE
SENSE¯
BOOST
INTV
OSENSE
PGND
V
SW
I
V
BG
TG
ON
CC
CC
IN
+
OUT
Q
330k
+
< 30 A
®
CMDSH-3
0.33 F
4.7 F
Processors
U
IRF7811W
IRF7811W
3
2
Current Mode Step-Down Controller
1 H
L1
UPS840
3720 F01a
+
C
OUT
L1: SUMIDA CEP125-IROMC
: CORNELL DUBILIER
DESCRIPTIO
The LTC
regulator controller for CPU power. An output voltage
between 1.05V and 1.825V is selected by a 5-bit code
(Intel VRM8.5 VID specification). The controller uses a
valley current control architecture to deliver very low duty
cycles without requiring a sense resistor. Operating fre-
quency is selected by an external resistor and is compen-
sated for variations in V
Discontinuous mode operation provides high efficiency
operation at light loads. A forced continuous control pin
reduces noise and RF interference and can assist second-
ary winding regulation by disabling discontinuous mode
operation when the main output is lightly loaded.
Fault protection is provided by internal foldback current
limiting, an output overvoltage comparator and optional
short-circuit shutdown timer. Soft-start capability for sup-
ply sequencing is accomplished using an external timing
capacitor. The regulator current limit level is also user
programmable. Wide supply range allows operation from
4V to 36V at the input.
No R
Pentium is a registered trademark of Intel Corporation.
10 F
C
270 F
2V
ESRE271M02B
5
OUT
4
, LTC and LT are registered trademarks of Linear Technology Corporation.
SENSE
V
5V TO 24V
V
1.05V TO 1.825V
20A
IN
OUT
is a trademark of Linear Technology Corporation.
®
3720 is a synchronous step-down switching
Single Phase VRM8.5
U
100
95
90
85
80
75
70
65
60
55
0.01
IN
V
L1 = 1 H
Efficiency vs Output Current
OUT
and V
= 1.45V
0.1
OUTPUT CURRENT (A)
OUT
V
IN
V
IN
= 5V
.
= 15V
1
LTC3720
10
3720 F01b
100
1
3720f

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LTC3720EGN Summary of contents

Page 1

... The regulator current limit level is also user programmable. Wide supply range allows operation from 4V to 36V at the input. , LTC and LT are registered trademarks of Linear Technology Corporation trademark of Linear Technology Corporation. SENSE Pentium is a registered trademark of Intel Corporation. ...

Page 2

... CC CC TG, BG, INTV , EXTV RMS Currents .............. 50mA CC CC Operating Ambient Temperature Range LTC3720EGN (Note 2) ........................ – Junction Temperature (Note 3) ............................ 125 C Storage Temperature Range ................. – 150 C Lead Temperature (Soldering, 10 sec).................. 300 C ELECTRICAL CHARACTERISTICS temperature range, otherwise specifications are T SYMBOL PARAMETER Main Control Loop ...

Page 3

... Specifications over the – operating temperature range are assured by design, characterization and correlation with statistical process controls. Note calculated from the ambient temperature T J dissipation P as follows: D LTC3720EGN • Note 4: The LTC3720 is tested in a feedback loop that adjusts V a specified error amplifier output voltage (I ) ...

Page 4

LTC3720 W U TYPICAL PERFOR A CE CHARACTERISTICS Current Sense Threshold vs I Voltage TH 300 RNG 200 1.4V 1V 0.7V 100 0.5V 0 –100 –200 0 1.0 1.5 2.0 2.5 3.0 0.5 I VOLTAGE (V) TH ...

Page 5

W U TYPICAL PERFOR A CE CHARACTERISTICS Error Amplifier g vs Temperature m 2.0 1.8 1.6 1.4 1.2 1.0 –50 – 100 125 TEMPERATURE ( C) 3720 G10 EXTV Switch Resistance CC vs Temperature 10 8 ...

Page 6

LTC3720 W U TYPICAL PERFOR A CE CHARACTERISTICS Transient Response (Forced Continuous Mode) V OUT 50mV/DIV I L 10A/DIV 20 s/DIV LOAD STEP = 0A TO 15A V = 15V 1.5V OUT FCB = 0V FIGURE 7 ...

Page 7

CTIO S V (Pin 18): Power Supply Voltage for VID. Range is from CC 3.1V to 5.5V. EXTV (Pin 19): External V Input. When EXTV CC CC ceeds 4.7V, an internal switch connects this pin ...

Page 8

LTC3720 CTIO AL DIAGRA 0.7V 2.4V 1 OST V VON t = (10pF ION S 20k + + I CMP – – 1.4V V RNG 4 ...

Page 9

U OPERATIO (Refer to Functional Diagram) Main Control Loop The LTC3720 is a current mode controller for DC/DC step-down converters. In normal operation, the top MOSFET is turned on for a fixed interval determined by a one-shot timer OST. When ...

Page 10

LTC3720 U U APPLICATIO S I FOR ATIO The basic LTC3720 application circuit is shown in Figure 1. External component selection is primarily de- termined by the maximum load current and begins with the selection of the sense resistance and ...

Page 11

U U APPLICATIO S I FOR ATIO 2.0 1.5 1.0 0 – JUNCTION TEMPERATURE ( C) Figure 2. R vs. Temperature DS(ON) the load current. When the LTC3720 is operating in continuous mode, the duty cycles ...

Page 12

LTC3720 U U APPLICATIO S I FOR ATIO R VON1 30k V OUT C VON R VON2 0.01 F 100k (3a) Figure 3. Correcting Frequency Shift with Load Current Changes shown in Figure 3a. Place capacitance ...

Page 13

U U APPLICATIO S I FOR ATIO This formula has a maximum This simple worst-case condition is RMS OUT(MAX) commonly used for design because even significant deviations do not offer much relief. Note ...

Page 14

LTC3720 U U APPLICATIO S I FOR ATIO + OPTIONAL LTC3720 EXTV CC EXTV SW CC CONNECTION 5V < V < SEC + FCB SENSE R3 BG SGND PGND Figure 4. Secondary Output Loop and ...

Page 15

... I 0 1.200V The junction temperature can be estimated from the 1 1.225V equations given in Note 3 of the Electrical Characteristics. 0 1.150V For example, the LTC3720EGN is limited to less than 1 1.175V 19mA from a 30V supply: 0 1.100V (19mA)(30V)(95 C/W) = 125 1.125V For larger currents, consider using an external supply with 0 1 ...

Page 16

LTC3720 U U APPLICATIO S I FOR ATIO External Gate Drive Buffers The LTC3720 drivers are adequate for driving up to about 60nC into MOSFET switches with RMS currents of 50mA. Applications with larger MOSFET switches or operating at higher ...

Page 17

U U APPLICATIO S I FOR ATIO operation can prove annoying during troubleshooting. The feature can be overridden by adding a pull-up current greater than the RUN/SS pin. The additional current prevents the discharge of C also ...

Page 18

LTC3720 U U APPLICATIO S I FOR ATIO Design Example As a design example, take a supply with the following specifications 24V (15V nominal 1.825V with typical at 1.5V, I OUT(MAX) First, calculate ...

Page 19

U U APPLICATIO S I FOR ATIO However 15A load step will cause an output change (ESR) = (15A) (0.005 ) = 75mV OUT(STEP) LOAD The complete circuit is shown in ...

Page 20

LTC3720 U U APPLICATIO S I FOR ATIO By positioning the output voltage 60mV above the regula- tion point at no load, it will only drop 65mV below the regulation point after the load step, well within the 100mV tolerance. ...

Page 21

... Figure 8. 15A CPU Core Voltage Regulator with Active Voltage Positioning at 300kHz V OUT 100mV/DIV 1. 10A/DIV 270 F 20 s/DIV OUT V = 15V IN FIGURE 7 CIRCUIT Figure 9. Normal Transient Response ( positioning accomplishes this with only three output ca- pacitors rather than five. Refer to Linear Technology Design Solutions 10 for additional information about active voltage positioning 0. RUN/SS BOOST ...

Page 22

LTC3720 U U APPLICATIO S I FOR ATIO PC Board Layout Checklist When laying out the printed circuit board, use the follow- ing checklist to ensure proper operation of the controller. These items are also illustrated in Figure 11. • ...

Page 23

... FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen- tation that the interconnection of its circuits as described herein will not infringe on existing patent rights. ...

Page 24

... Dual, 550kHz, 2-Phase Synchronous Step-Down Controllers LTC3728/LTC3728L LTC3730/LTC3732 3-Phase Synchronous DC/DC Step-Down Controllers LTC3831 DDR Memory Termination Power Supply Burst Mode is registered trademark of Linear Technology Corporation. Linear Technology Corporation 24 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 COMMENTS Power Good Output, Minimum Input/Output Capacitors, 3 ...

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