LTC1143 Linear Technology, LTC1143 Datasheet

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LTC1143

Manufacturer Part Number
LTC1143
Description
Dual High Efficiency SO-16 Step-Down Switching Regulator Controllers
Manufacturer
Linear Technology
Datasheet

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APPLICATIONS
FEATURES
TYPICAL
3.3V/2A
High Efficiency Maintained over Three Decades of
Dual Outputs
Very High Efficiency: Over 95% Possible
Current Mode Operation for Excellent Line and Load
Transient Response
Output Current
Low Standby Current at Light Loads: 160 A/Output
Logic-Controlled Shutdown (LTC1143, LTC1143L)
Wide V
(LTC1143L, LTC1143L-ADJ)
Very Low Dropout Operation: 100% Duty Cycle
Available in Narrow 16-Pin SO Package
Personal Digital Assistants
Notebook and Palmtop Computers
Battery-Operated Digital Devices
Portable Instruments
DC Power Distribution Systems
V
C
220 F
L1, L2: SUMIDA CDRH125-270
P1: SILICONIX Si4953DY/FAIRCHILD NDS8947
R
OUT1
OUT1
SENSE1,
10V
LTC1143, LTC1143L: 3.3V, 5V
LTC1143L-ADJ: Dual Adjustable
2
49.9k
R
R
+
IN
SENSE2
0.05
1%
SENSE1
R1
Range: 3.5V to 16V
APPLICATION
: DALE WSL-2010-.05
R2
82.5k
1%
27 H
+
U
L1
100pF
C
22 F
25V
IN1
2
P1A
1000pF
D1
MBRS320T3
0.22 F
U
16
4
1
2
Figure 1. High Efficiency Dual 3.3V/2.5V Regulator
P-DRIVE 1
SENSE
SENSE
V
FB1
GND1
V
IN1
13
300pF
3
+
C
1
1
T1
C
T1
14
I
TH1
15
R
1k
C1
C
3300pF
LTC1143L-ADJ
C1
4V TO 14V
Step-Down Switching Regulator
V
IN
3300pF
DESCRIPTION
The LTC1143 series is a dual step-down switching regulator
controller featuring automatic Burst Mode
maintain high efficiencies at low output currents. This
device is composed of two separate regulator blocks,
each driving an external power MOSFET at switching
frequencies up to 400kHz using a constant off-time current
mode architecture. Both fixed and adjustable voltages are
available.
The operating current level for both regulators is user-
programmable via an external current sense resistor.
Wide input supply range allows operation from 4V to 14V
(16V maximum). The LTC1143L and LTC1143L-ADJ
extend operation to V
low dropout regulation limited only by the R
external MOSFET and resistance of the inductor and
current sense resistor.
The LTC1143 series is ideal for applications requiring dual
output voltages with high conversion efficiencies over a
wide load current range in a small amount of board space.
Burst Mode is a trademark of Linear Technology Corporation.
C
C2
, LTC and LT are registered trademarks of Linear Technology Corporation.
I
TH2
7
R
1k
Dual High Efficiency SO-16
C2
C
T2
6
C
300pF
P-DRIVE 2
T2
SENSE
SENSE
GND2
5
V
IN2
V
11
FB2
+
2
2
U
9
8
10
12
MBRS320T3
IN
LTC1143/LTC1143L
0.22 F
= 3.5V. 100% duty cycle provides
1000pF
D2
P1B
LTC1143L-ADJ
100pF
27 H
L2
+
49.9k
Controllers
1%
R4
C
22 F
25V
IN2
R
2
0.05
SENSE2
R3
49.9k
1%
TM
DS(ON)
operation to
+
1143 F01
C
220 F
10V
V
2.5V/2A
OUT2
2
OUT2
of the
1

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LTC1143 Summary of contents

Page 1

... R external MOSFET and resistance of the inductor and current sense resistor. The LTC1143 series is ideal for applications requiring dual output voltages with high conversion efficiencies over a wide load current range in a small amount of board space. , LTC and LT are registered trademarks of Linear Technology Corporation. ...

Page 2

... LTC1143L-ADJ ABSOLUTE MAXIMUM Input Supply Voltage (Pins 5,13) ............... 16V to –0.3V Continuous Output Current (Pins 4,12) ................ 50mA Sense Voltages (Pins 16) V 12.7V .......................................... 13V to – 0. < 12.7V .............................. (V IN Shutdown Voltage (LTC1143, LTC1143L, Pins 2, 10)...........7V to – 0.3V U PACKAGE/ORDER INFORMATION TOP VIEW + – SENSE SENSE 3 SHUTDOWN 3 2 ...

Page 3

... See Applications Information. and power Note 3: In applications where R A off-time increases approximately 40%. Note 4: The LTC1143 series is guaranteed to meet specified performance from and is designed, characterized and expected to meet these extended temperature limits, but is not tested at – LTC1143/LTC1143L LTC1143L-ADJ ...

Page 4

... NOT INCLUDING PINS 5, 13 GATE CHARGE CURRENT 1.8 1.5 ACTIVE MODE 1.2 PER REGULATOR BLOCK 0.9 0.6 0.3 SLEEP MODE INPUT VOLTAGE (V) LTC1143 • G07 4 3.3V Output Efficiency 100 10V 100 1000 LOAD CURRENT (mA) LTC1143 G02 Line Regulation 40 ...

Page 5

... MOSFET, 5V Section. Voltage swing at this pin is from V to ground. IN5 LTC1143/LTC1143L LTC1143L-ADJ Current Sense Threshold Voltage 175 MAXIMUM THRESHOLD 150 125 100 75 50 MINIMUM THRESHOLD TEMPERATURE (°C) LTC1143 G12 sets the current trip threshold SENSE < 100 ...

Page 6

... SENSE 3 (Pin 16): Connects to internal resistive divider which sets the output voltage for the 3.3V section. Pin 16 is also the (–) input for the current comparator on the 3.3V section. LTC1143L-ADJ + SENSE 1 (Pin 1): The (+) Input to the Section 1 Current Comparator. A built-in offset between Pins 1 and 16 in ...

Page 7

... U U FUNCTIONAL DIAGRA Only one regulator block shown. Connections shown for LT1143/LTC1143L; changes create LTC1143L-ADJ SLEEP – – V TH1 V TH2 T + OFF-TIME 14(6) CONTROL OPERATION Refer to Functional Diagram and Figure 1. The LTC1143 series consists of two individual regulator blocks, each using current mode, constant off-time archi- tectures to switch an external power MOSFET ...

Page 8

... Burst Mode operation, a built-in offset ( APPLICATIONS INFORMATION The basic LTC1143L-ADJ application circuit is shown in Figure 1. The LTC1143 and LTC1143L are similar but omit the external resistive V dividers (see Figures 10 and OUT 13). External component selection is driven by the load requirement and begins with V ...

Page 9

... The resulting reduced to approximately I SC(AVG) L and C Selection for Operating Frequency T Each regulator section of the LTC1143 series uses a constant off-time architecture with t external timing capacitor C . Each time the P-channel T MOSFET switch turns on the voltage on C approximately 3.3V. During the off-time, C ...

Page 10

... If too small an inductor is used, the inductor current will become discontinuous before the LTC1143 series enters Burst Mode operation. A consequence of this is that the LTC1143 series will delay entering Burst Mode operation and efficiency will be degraded at low currents. Inductor Core Selection Once the minimum value for L is known, the type of inductor must be selected ...

Page 11

... Always consult the manufacturer if there is any question. An additional 0 ceramic capacitor is also required on each V frequency decoupling. The selection of C ESR of C OUT for proper operation of the LTC1143 series: C Required ESR < 2R OUT Optimum efficiency is obtained by making the ESR equal to R SENSE efficiency degrades by less than 1% ...

Page 12

... 10V the DC supply current for each section is 160 A IN for no load and increases proportionally with load constant 1.6mA after the LTC1143 series has entered continuous mode. Because the DC bias current is can be monitored for OUT causing a rapid drop regulator can ...

Page 13

... losses cause the Shutdown Considerations Pins 2 and 10 on the LTC1143 and LTC1143L shut down their respective sections when pulled high. They require CMOS logic level signals with t be floated. The LTC1143L-ADJ gives up the pin-controlled shutdown function in order to gain feedback pins for programming the output voltages ...

Page 14

... LTC1143/LTC1143L LTC1143L-ADJ U U APPLICATIONS INFORMATION The LTC1143L-ADJ outputs can be turned off in one of two ways placing a power MOSFET switch in the V to the entire regulator pulling the V 1.4V, which trips comparator V and forces P-DRIVE high (see Functional Diagram). V can be pulled high with a ...

Page 15

... Check the following in your layout: > 5A) OUT 1) Are the signal and power grounds segregated? The LTC1143 series GND Pin 3 (11) must return separately – pin to to: a) the power and b) the signal grounds. The power ground returns to the anode of the Schottky diode and (– ...

Page 16

... V C OUT3 OUT3 – *MUST BE LOCATED CLOSE TO LTC1143 BOLD LINES INDICATE HIGH CURRENT PATHS Figure 9. LTC1143 Layout Diagram (see Board Layout Checklist high impedance and must not be allowed to float. Both pins can be driven by the same external signal if needed. 7) For the LTC1143L-ADJ, are the V ...

Page 17

... TH2 T2 TH1 510 220pF 3300pF 3300pF P1: IR IRF7406 L1: SUMIDA CDRH125-150 P2: IR IRF7204 L2: SUMIDA CDRH125-270 LTC1143/LTC1143L LTC1143L-ADJ + C + IN5 22 F 25V 2 5 P1B V IN5 P-DRIVE 5 SENSE5 SENSE 5 0.01 F – SENSE GND5 MBRS140T3 ...

Page 18

... AVX TPSD226K025R0200 IN1 IN2 AVX TPSE227M010R0100 OUT1 OUT2 L1: SUMIDA CDRH125-270 L2: PULSE ENGINEERING PE-53718 3.5V TO 10V 13 V IN1 P-DRIVE 1 P-DRIVE 2 + SENSE 1 SENSE LTC1143L-ADJ – SENSE 1 SENSE V FB1 C GND1 TH2 T2 TH1 ...

Page 19

... DWG # 05-08-1610 0.228 – 0.244 (5.791 – 6.197 0.053 – 0.069 (1.346 – 1.752) 0.014 – 0.019 (0.355 – 0.483) LTC1143/LTC1143L LTC1143L-ADJ 0.386 – 0.394* (9.804 – 10.008 0.150 – 0.157** (3.810 – 3.988 0.004 – ...

Page 20

... R : KRL SL-1/2-C1-0R033J SENSE3 R : KRL SL-1/2-C1-0R050J SENSE5 Synchronous Equivalent to LTC1143, 4V < V Synchronous Equivalent to LTC1143L-ADJ, 3.5V < < V (1/2) LTC1143L-ADJ in SO-8 Single Channel with Internal Switch Constant Frequency Current Mode, Drives Synchronous N-Channel MOSFETS Up to Four Output Voltages from G28 Package Full Featured Dual Controller in G36 Package ...

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