LT1959CR#TRPBF Linear Technology, LT1959CR#TRPBF Datasheet

IC SW REG STEP-DWN 500KHZ 7-DD

LT1959CR#TRPBF

Manufacturer Part Number
LT1959CR#TRPBF
Description
IC SW REG STEP-DWN 500KHZ 7-DD
Manufacturer
Linear Technology
Type
Step-Down (Buck)r
Datasheet

Specifications of LT1959CR#TRPBF

Internal Switch(s)
Yes
Synchronous Rectifier
No
Number Of Outputs
1
Voltage - Output
1.21 ~ 38 V
Current - Output
4.5A
Frequency - Switching
500kHz
Voltage - Input
4.3 ~ 15 V
Operating Temperature
0°C ~ 125°C
Mounting Type
Surface Mount
Package / Case
D²Pak, TO-263 (7 leads + tab)
Dc To Dc Converter Type
Step Down
Pin Count
7 +Tab
Input Voltage
16V
Output Voltage
1.21 to 2.42V
Switching Freq
540kHz
Output Current
8.5A
Package Type
DDPAK
Output Type
Adjustable
Switching Regulator
Yes
Line Regulation
0.03%/V
Mounting
Surface Mount
Input Voltage (min)
4V
Operating Temperature Classification
Commercial
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Power - Output
-
Lead Free Status / Rohs Status
Compliant

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LT1959CR#TRPBFLT1959CR
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LT1959CR#TRPBFLT1959CR
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FEATURES
TYPICAL
APPLICATIO S
Operates with Input as Low as 4V
Output Range Down to 1.21V
Constant 500kHz Switching Frequency
Uses All Surface Mount Components
Inductor Size Reduced to 1.8 H
Saturating Switch Design: 0.07
Shutdown Current: 15 A
Easily Synchronizable
Cycle-by-Cycle Current Limiting
4.5A Switch
Current Mode Control
Portable Computers
Battery-Powered Systems
Battery Chargers
Distributed Power
5V to 3.3V Conversion
5V to 2.5V Conversion
5V to 1.8V Conversion
INPUT
CERAMIC
5V
10 F TO
50 F
C3
APPLICATION
+
OPEN
HIGH
U
= ON
5V to 1.8V Down Converter
OR
1N914
D2
V
SHDN
IN
GND
LT1959
BOOST
U
V
C
V
C
1.5nF
SW
FB
C
C2
0.68 F
D1
MBRS330T3
5 H
L1
R2
2.49k
1.21k
R1
+
DESCRIPTIO
The LT
regulator functionally identical to the LT1506 but optimized
for lower output voltage applications. It will operate down
to 1.21V output compared to 2.42V for the LT1506. A 4.5A
switch is included on the die along with all the necessary
oscillator, control and logic circuitry. High switching fre-
quency allows a considerable reduction in the size of ex-
ternal components. The topology is current mode for fast
transient response and good loop stability.
A special high speed bipolar process and new design tech-
niques achieve high efficiency at high switching frequency.
Efficiency is maintained over a wide output current range
by keeping quiescent supply current to 3.8mA and by uti-
lizing a supply boost capacitor to saturate the power switch.
The LT1959 fits into standard 7-pin DD and fused lead
SO-8 packages. Full cycle-by-cycle short-circuit protection
and thermal shutdown are provided. Standard surface
mount external parts are used, including the inductor and
capacitors. There is the optional function of shutdown or
synchronization. A shutdown signal reduces supply current
to 15 A. Synchronization allows an external logic level sig-
nal to increase the internal oscillator from 580kHz to 1MHz.
1959 TA01
, LTC and LT are registered trademarks of Linear Technology Corporation.
C1
100 F, 10V
SOLID
TANTALUM
OUTPUT
1.8V
4A
4.5A, 500kHz Step-Down
®
1959 is a 500kHz monolithic buck mode switching
Switching Regulator
90
85
80
75
70
U
0
0.5
Efficiency vs Load Current
1.0
LOAD CURRENT (A)
1.5
2.0
2.5
V
V
L = 10 H
3.0
OUT
IN
= 5V
LT1959
= 3.3V
3.5
1959 TA02
4.0
1

Related parts for LT1959CR#TRPBF

LT1959CR#TRPBF Summary of contents

Page 1

... There is the optional function of shutdown or synchronization. A shutdown signal reduces supply current Synchronization allows an external logic level sig- nal to increase the internal oscillator from 580kHz to 1MHz. , LTC and LT are registered trademarks of Linear Technology Corporation OUTPUT 1 ...

Page 2

LT1959 ABSOLUTE MAXIMUM Input Voltage .......................................................... 16V BOOST Voltage ........................................................ 30V BOOST Pin Above Input Voltage ............................. 15V SHDN Pin Voltage ..................................................... 7V FB Pin Voltage ....................................................... 3.5V FB Pin Current ....................................................... 1mA U PACKAGE/ORDER INFORMATION FRONT ...

Page 3

ELECTRICAL CHARACTERISTICS temperature range, otherwise specifications are at T otherwise noted. PARAMETER Switch On Resistance (Note 7) Maximum Switch Duty Cycle Switch Frequency Switch Frequency Line Regulation Frequency Shifting Threshold on FB Pin Minimum Input Voltage (Note 3) Minimum Boost ...

Page 4

LT1959 W U TYPICAL PERFORMANCE CHARACTERISTICS Minimum Input Voltage with 3.3V Output 4.7 4.5 4.3 4.1 3.9 3.7 3.5 3 100 1000 LOAD CURRENT (mA) 1959 G01 Shutdown Pin Bias Current –500 AT 0.37V SHUTDOWN THRESHOLD. AFTER SHUTDOWN, ...

Page 5

W U TYPICAL PERFORMANCE CHARACTERISTICS Frequency Foldback 500 SWITCHING FREQUENCY 400 300 200 100 FEEDBACK PIN CURRENT 0 0 0.2 0.4 0.6 0.8 1.0 1.2 FEEDBACK PIN VOLTAGE (V) 1959 • G10 Maximum Load Current 3.3V OUT ...

Page 6

LT1959 PIN FUNCTIONS FB: The feedback pin is used to set output voltage using an external voltage divider that generates 1.21V at the pin with the desired output voltage. Three additional functions are performed by the FB ...

Page 7

W BLOCK DIAGRAM The LT1959 is a constant frequency, current mode buck converter. This means that there is an internal clock and two feedback loops that control the duty cycle of the power switch. In addition to the normal error ...

Page 8

LT1959 U U APPLICATIONS INFORMATION FEEDBACK PIN FUNCTIONS The feedback (FB) pin on the LT1959 is used to set output voltage and provide several overload protection features. The first part of this section deals with selecting resistors to set output ...

Page 9

U U APPLICATIONS INFORMATION The internal circuitry which forces reduced switching frequency also causes current to flow out of the feedback pin when output voltage is low. The equivalent circuitry is shown in Figure completely off during ...

Page 10

... After making an initial choice, consider the secondary things like output voltage ripple, second sourcing, etc. Use the experts in the Linear Technology’s applica- tions department if you feel uncertain about the final choice. They have experience with a wide range of inductor types and can tell you about the latest devel- opments in low profile, surface mounting, etc ...

Page 11

U U APPLICATIONS INFORMATION Table 2 SERIES VENDOR/ VALUE DC CORE RESIS- PART NO (Amps) TYPE TANCE( ) Coiltronics CTX2-1 2 4.1 Tor 0.011 CTX5-4 5 4.4 Tor 0.019 CTX8-4 8 3.5 Tor 0.020 CTX2-1P 2 3.4 Tor ...

Page 12

LT1959 U U APPLICATIONS INFORMATION Ceramic Capacitors Higher value, lower cost ceramic capacitors are now available in smaller case sizes. These are ideal for input bypassing because of their high ripple rating and tolerance to turn-on surges. As output capacitors, ...

Page 13

U U APPLICATIONS INFORMATION and does not fall to less than 1/3 of nominal output voltage, foldback will not take effect. With the overloaded condi- tion, output current will increase to a typical value of 5.7A, determined by peak switch ...

Page 14

LT1959 U U APPLICATIONS INFORMATION INPUT Keep the connections from the resistors to the shutdown pin short and make sure that interplane or surface capaci- tance to the switching nodes are minimized. If high resistor ...

Page 15

U U APPLICATIONS INFORMATION from the switch node. Also note that the high current ground path of the catch diode and input capacitor are kept very short and separate from the analog ground line. The high speed switching current path ...

Page 16

LT1959 U U APPLICATIONS INFORMATION PARASITIC RESONANCE Resonance or “ringing” may sometimes be seen on the switch node (see Figure 7). Very high frequency ringing following switch rise time is caused by switch/diode/input capacitor lead inductance and diode capacitance. Schot- ...

Page 17

U U APPLICATIONS INFORMATION The term inside the radical has a maximum value of 0.5 when input voltage is twice output, and stays near 0.5 for a relatively wide range of input voltages common practice therefore to simply ...

Page 18

LT1959 U U APPLICATIONS INFORMATION formulas show how to calculate each of these losses. These formulas assume continuous mode operation, so they should not be used for calculating efficiency at light load currents. Switch loss ...

Page 19

U U APPLICATIONS INFORMATION 40 GAIN 20 0 PHASE –20 –40 10 100 1k 10k FREQUENCY (Hz) Figure 10. Response from V C Error amplifier transconductance phase and gain are shown in Figure 11. The error amplifier can be modeled ...

Page 20

LT1959 U U APPLICATIONS INFORMATION G = Transconductance of power stage = 5.3A Error amplifier transconductance = 2(10 MA ESR = Output capacitor ESR 1.21 = Reference voltage With and ESR = 0.03 , ...

Page 21

U U APPLICATIONS INFORMATION ADJUSTABLE INPUT SUPPLY 10mV/DIV 5A/DIV 0.2ms/DIV Figure 14. Loop Stability Check The output of the regulator contains both the desired low frequency transient information and a reasonable amount of high frequency (500kHz) ripple. The ripple makes ...

Page 22

LT1959 U U APPLICATIONS INFORMATION converters 120 out of phase with each other reduces input and output ripple currents. This reduces the ripple rating, size and cost of filter capacitors. Current Sharing/Split Input Supplies Current sharing is accomplished by joining ...

Page 23

... Figure 16. Buck Converter with Adjustable Soft Start 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

... Synchronous Step-Down Switching Regulator Controller High Efficiency, Low Ripple LTC1735 High Efficiency Step-Down Converter LT1775 High Power NoR SENSE trademark of Linear Technology Corporation SENSE Linear Technology Corporation 24 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 www.linear-tech.com U Dimensions in inches (millimeters) unless otherwise noted. ...

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