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FEATURES
n
Wide Input Range: 3.6V to 36V
n
5V at 600mA from 16V to 36V Input
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3.3V at 600mA from 12V to 36V Input
n
5V at 500mA from 6.3V to 36V Input
n
3.3V at 500mA from 4.5V to 36V Input
n
Fixed Frequency 500kHz Operation
n
Uses Tiny Capacitors and Inductors
n
Soft-Start
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Internally Compensated
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Low Shutdown Current: <2μA
n
Output Adjustable Down to 1.25V
n
Low Profi le (1mm) SOT-23 (ThinSOT™) and
(2mm × 3mm × 0.75mm) 6-Pin DFN Packages
APPLICATIONS
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Automotive Battery Regulation
n
Industrial Control Supplies
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Wall Transformer Regulation
n
Distributed Supply Regulation
n
Battery-Powered Equipment
TYPICAL APPLICATION
3.3V Step-Down Converter
V
IN
V
BOOST
IN
4.5V TO 36V
LT1933
SHDN
OFF ON
GND
2.2μF
1N4148
0.1μF
22μH
SW
FB
MBRM140
16.5k
10k
600mA, 500kHz Step-Down
Switching Regulator in
SOT-23 and DFN Packages
DESCRIPTION
The LT
®
1933 is a current mode PWM step-down DC/DC
converter with an internal 0.75A power switch, packaged
in a tiny 6-lead SOT-23. The wide input range of 3.6V
to 36V makes the LT1933 suitable for regulating power
from a wide variety of sources, including unregulated wall
transformers, 24V industrial supplies and automotive
batteries. Its high operating frequency allows the use of
tiny, low cost inductors and ceramic capacitors, resulting
in low, predictable output ripple.
Cycle-by-cycle current limit provides protection against
shorted outputs, and soft-start eliminates input current
surge during start up. The low current (<2μA) shutdown
provides output disconnect, enabling easy power manage-
ment in battery-powered systems.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. ThinSOT is a trademark of Linear Technology Corporation. All other
trademarks are the property of their respective owners.
95
90
85
V
OUT
80
3.3V/500mA
75
22μF
70
65
1933 TA01a
0
Effi ciency
V
= 12V
IN
V
= 5V
OUT
V
= 3.3V
OUT
100
200
500
300
400
LOAD CURRENT (mA)
1933 TA01b
LT1933
600
1933fe
1
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Related Manuals for Linear Technology LT1933
Summary of Contents for Linear Technology LT1933
- Page 1 APPLICATIONS L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. ThinSOT is a trademark of Linear Technology Corporation. All other Automotive Battery Regulation trademarks are the property of their respective owners.
-
Page 2: Absolute Maximum Ratings
LT1933 ABSOLUTE MAXIMUM RATINGS (Note 1) LT1933I ..........–40°C to 125°C Input Voltage (V ) ........–0.4V to 36V LT1933H ..........–40°C to 150°C BOOST Pin Voltage ...........43V Maximum Junction Temperature BOOST Pin Above SW Pin .........20V LT1933E, LT1933I ..........125°C SHDN Pin ........... -
Page 3: Electrical Characteristics
LT1933 ELECTRICAL CHARACTERISTICS denotes the specifi cations which apply over the full operating temperature range, otherwise specifi cations are at T = 25°C. V = 12V, V = 17V, unless otherwise noted. (Note 2) BOOST PARAMETER CONDITIONS UNITS Undervoltage Lockout 3.35... - Page 4 LT1933 TYPICAL PERFORMANCE CHARACTERISTICS Effi ciency, V = 5V Effi ciency, V = 3.3V Switch Current Limit 1200 = 25°C = 25°C = 25°C = 5V = 3.3V TYPICAL 1000 = 12V = 5V MINIMUM = 12V = 24V = 24V...
- Page 5 LT1933 TYPICAL PERFORMANCE CHARACTERISTICS SHDN Pin Current Frequency Foldback Soft-Start = 25°C = 25°C = 25°C DC = 30% SHDN PIN VOLTAGE (V) SHDN PIN VOLTAGE (V) FB PIN VOLTAGE (V) 1933 G10 1933 G11 1933 G12 Typical Minimum Input Voltage...
-
Page 6: Block Diagram
LT1933 PIN FUNCTIONS (SOT-23/DFN) SHDN (Pin 4): The SHDN pin is used to put the LT1933 in BOOST (Pin 1): The BOOST pin is used to provide a drive voltage, higher than the input voltage, to the internal bipolar shutdown mode. Tie to ground to shut down the LT1933. - Page 7 fl op, turning on the internal 750mA power switch Q1. An to prevent switching when V is less than ~3.35V. The SHDN pin is used to place the LT1933 in shutdown, dis- amplifi er and comparator monitor the current fl owing between the V...
- Page 8 500mA, then you can decrease the value of the inductor and operate with higher ripple current. This Bypass the input of the LT1933 circuit with a 2.2μF or allows you to use a physically smaller inductor, or one higher value ceramic capacitor of X7R or X5R type.
- Page 9 fi lters the square wave generated that is intended for use in switching regulators. The ESR by the LT1933 to produce the DC output. In this role it should be specifi ed by the supplier, and should be 0.1Ω...
- Page 10 LT1933 APPLICATIONS INFORMATION Figure 1 shows the transient response of the LT1933 with drop) resulting from a larger output capacitor and a phase several output capacitor choices. The output is 3.3V. The lead capacitor. The last photo shows the response to a high load current is stepped from 100mA to 400mA and back to performance electrolytic capacitor.
- Page 11 If the input voltage is ramped slowly, or the 1N4148 or 1N914) will work well. Figure 2 shows two LT1933 is turned on with its SHDN pin when the output ways to arrange the boost circuit. The BOOST pin must is already in regulation, then the boost capacitor may not be at least 2.3V above the SW pin for best effi...
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Page 12: Out
5V/DIV 50μs/DIV 5V/DIV SHDN 0.1μF 100mA/DIV 1933 F04b 5V/DIV 0.5ms/DIV Figure 4. To Soft-Start the LT1933, Add a Resistor and Capacitor to the SHDN Pin. V = 12V, V = 3.3V, C = 22μF , R = 10Ω LOAD 1933fe... - Page 13 OR-ed with the LT1933’s pin is allowed to fl oat and the SHDN pin tors can cause problems if the LT1933 is plugged into a output. If the V live supply (see Linear Technology Application Note 88 for is held high (either by a logic signal or because it is tied a complete discussion).
- Page 14 2.2μF AI.EI. 5A/DIV 20μs/DIV (6b) 1Ω LT1933 20V/DIV 0.1μF 2.2μF 5A/DIV 1933 F06 20μs/DIV (6c) Figure 6. A Well Chosen Input Network Prevents Input Voltage Overshoot and Ensures Reliable Operation When the LT1933 is Connected to a Live Supply 1933fe...
- Page 15 This simplifi es loop compensation. In particular, discussion of loop compensation and describes how to the LT1933 does not require the ESR of the output capaci- test the stability using a transient load. tor for stability allowing the use of ceramic capacitors to achieve low output ripple and small circuit size.
- Page 16 fl ow in the LT1933’s V and SW pins, the catch two vias near the GND pin of the LT1933 to help remove diode (D1) and the input capacitor (C2). The loop formed heat from the LT1933 to the ground plane.
-
Page 17: Vin(Max) = (V Out
LT1933 TYPICAL APPLICATIONS 3.3V Step-Down Converter 4.5V TO BOOST LT1933 0.1μF 22μH SHDN 3.3V/ OFF ON 500mA 16.5k 2.2μF 22μF 6.3V 1933 TA02b 12V Step-Down Converter D3, 6V 14.5V TO BOOST LT1933 0.1μF 47μH SHDN OFF ON 12V/ 450mA 86.6k 2.2μF... - Page 18 LT1933 PACKAGE DESCRIPTION DCB Package 6-Lead Plastic DFN (2mm × 3mm) (Reference LTC DWG # 05-08-1715) 0.70 ±0.05 1.65 ±0.05 3.55 ±0.05 (2 SIDES) 2.15 ±0.05 PACKAGE OUTLINE 0.25 ± 0.05 0.50 BSC 1.35 ±0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS R = 0.115...
- Page 19 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 representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
- Page 20 = 2.5mA, I = 30μA, OUT(MIN) DC/DC Converter TSSOP16E Package Burst Mode is a registered trademark of Linear Technology Corporation. 1933fe LT 0409 REV E • PRINTED IN USA Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 www.linear.com...
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