Datasheet

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LT1934/LT1934-1

1934fe

TYPICAL APPLICATION

DESCRIPTION

Micropower Step-Down

Switching Regulators

in ThinSOT and DFN

The LT

1934 is a micropower step-down DC/DC converter

with internal 400mA power switch, packaged in a low

proﬁ le (1mm) ThinSOT. With its wide input range of 3.2V

to 34V, the LT1934 can regulate a wide variety of power

sources, from 4-cell alkaline batteries and 5V logic rails

to unregulated wall transformers and lead-acid batteries.

Quiescent current is just 12μA and a zero current shut-

down mode disconnects the load from the input source,

simplifying power management in battery-powered sys-

tems. Burst Mode

operation and the low drop internal

power switch result in high efﬁ ciency over a broad range

of load current.

The LT1934 provides up to 300mA of output current. The

LT1934-1 has a lower current limit, allowing optimum

choice of external components when the required output

current is less than 60mA. Fast current limiting protects

the LT1934 and external components against shorted

outputs, even at 34V input.

L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.

Burst Mode is a registered trademark of Linear Technology Corporation.

ThinSOT is a trademark of Linear Technology Corporation.

All other trademarks are the property of their respective owners.

FEATURES

APPLICATIONS

Wide Input Voltage Range: 3.2V to 34V

Micropower Operation: I

= 12μA

5V at 250mA from 6.5V to 34V Input (LT1934)

5V at 60mA from 6.5V to 34V Input (LT1934-1)

3.3V at 250mA from 4.5V to 34V Input (LT1934)

3.3V at 60mA from 4.5V to 34V Input (LT1934-1)

Low Shutdown Current: <1μA

Low V

CESAT

Switch: 200mV at 300mA

Low Proﬁ le (1mm) SOT-23 (ThinSOT™) and

(2mm × 3mm × 0.8mm) 6-Pin DFN Package

Wall Transformer Regulation

Automotive Battery Regulation

Standby Power for Portable Products

Distributed Supply Regulation

Industrial Control Supplies

3.3V Step-Down Converter

Efﬁ ciency

BOOST

LT1934

SHDN

1934 TA01

2.2μF

0.22μF

10pF

C1: SANYO 4TPB100M

C2: TAIYO YUDEN GMK325BJ225MN

D1: ON SEMICONDUCTOR MBR0540

D2: CENTRAL CMDSH-3

L1: SUMIDA CDRH4D28-470

OUT

3.3V

250mA

604k

47μH

4.5V TO 34V

ON OFF

GND

100μF

LOAD CURRENT (mA)

EFFICIENCY (%)

100

0.1 10 100

1934 TA02

LT1934

= 12V

OUT

= 5V

OUT

= 3.3V

Summary of content (20 pages)

PAGE 1
LT1934/LT1934-1 Micropower Step-Down Switching Regulators in ThinSOT and DFN FEATURES DESCRIPTION n The LT ®1934 is a micropower step-down DC/DC converter with internal 400mA power switch, packaged in a low proﬁle (1mm) ThinSOT. With its wide input range of 3.2V to 34V, the LT1934 can regulate a wide variety of power sources, from 4-cell alkaline batteries and 5V logic rails to unregulated wall transformers and lead-acid batteries.
PAGE 2
LT1934/LT1934-1 ABSOLUTE MAXIMUM RATINGS (Note 1) Input Voltage (VIN) ................................................... 34V BOOST Pin Voltage ................................................. 40V BOOST Pin Above SW Pin........................................ 20V SHDN Pin ................................................................. 34V FB Voltage .................................................................. 6V SW Voltage ...............................................................
PAGE 3
LT1934/LT1934-1 ELECTRICAL CHARACTERISTICS The l denotes the speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are at TA = 25°C. VIN = 10V, VBOOST = 15V, unless otherwise noted. SYMBOL CONDITIONS MIN Undervoltage Lockout Quiescent Current UNITS l l 3 3 3 3.2 3.6 3.6 V V V –40°C ≤ TA ≤ 85°C –40°C ≤ TA ≤ 125°C l l 12 12 12 22 26 26 μA μA μA 0.01 2 μA –40°C ≤ TA ≤ 85°C –40°C ≤ TA ≤ 125°C l l 1.25 1.25 1.27 1.27 V V VFB = 1.
PAGE 4
LT1934/LT1934-1 TYPICAL PERFORMANCE CHARACTERISTICS LT1934 Efﬁciency, VOUT = 5V LT1934 Efﬁciency, VOUT = 3.3V LT1934 VOUT = 3.3V L = 47μH 90 TA = 25°C VIN = 12V 80 EFFICIENCY (%) EFFICIENCY (%) LT1934 VOUT = 5V L = 47μH 90 TA = 25°C VIN = 24V 70 60 90 80 VIN = 24V VIN = 12V 70 50 100 1934 G03 Off Time vs Temperature 3.0 VIN = 12V VIN = 24V 70 60 10 300 200 100 2.0 1.5 1.0 LT1934-1 100 0.5 0 –50 50 1 2.
PAGE 5
LT1934/LT1934-1 TYPICAL PERFORMANCE CHARACTERISTICS Undervoltage Lockout vs Temperature 20 4.0 15 3.5 UVLO (V) QUIESCENT CURRENT (μA) Quiescent Current vs Temperature 10 5 3.0 2.5 0 –50 –25 75 0 25 50 TEMPERATURE (°C) 100 2.0 –50 125 –25 75 0 25 50 TEMPERATURE (°C) 100 1934 G10 1934 G11 Minimum Input Voltage VOUT = 5V Minimum Input Voltage VOUT = 3.3V 6.0 8 LT1934 VOUT = 5V TA = 25°C 7 BOOST DIODE TIED TO OUTPUT INPUT VOLTAGE (V) INPUT VOLTAGE (V) LT1934 VOUT = 3.3V 5.
PAGE 6
LT1934/LT1934-1 BLOCK DIAGRAM VIN VIN + C2 + – D2 BOOST ON TIME R Qa 12μs DELAY S OFF TIME SHDN L1 SW 1.8μs DELAY ON OFF C3 Q VOUT D1 C1 + VREF 1.
PAGE 7
LT1934/LT1934-1 OPERATION (Refer to Block Diagram) The LT1934 uses Burst Mode control, combining both low quiescent current operation and high switching frequency, which result in high efﬁciency across a wide range of load currents and a small total circuit size. A comparator monitors the voltage at the FB pin of the LT1934. If this voltage is higher than the internal 1.25V reference, the comparator disables the oscillator and power switch.
PAGE 8
LT1934/LT1934-1 APPLICATIONS INFORMATION Which One to Use: LT1934 or LT1934-1? The only difference between the LT1934 and LT1934-1 is the peak current through the internal switch and the inductor. If your maximum load current is less than 60mA, use the LT1934-1. If your maximum load is higher, use the LT1934; it can supply up to ~300mA. While the LT1934-1 can’t deliver as much output current, it has other advantages.
PAGE 9
LT1934/LT1934-1 APPLICATIONS INFORMATION Table 2. Inductor Vendors VENDOR PHONE URL PART SERIES COMMENTS Murata (404) 426-1300 www.murata.com LQH3C Small, Low Cost, 2mm Height Sumida (847) 956-0666 www.sumida.com CR43 CDRH4D28 CDRH5D28 Coilcraft (847) 639-6400 www.coilcraft.com DO1607C DO1608C DT1608C Würth Electronics (866) 362-6673 www.we-online.
PAGE 10
LT1934/LT1934-1 APPLICATIONS INFORMATION capacitor is subject to large surge currents if the LT1934 circuit is connected to a low impedance supply, and that some electrolytic capacitors (in particular tantalum) must be speciﬁed for such use. Output Capacitor and Output Ripple The output capacitor ﬁlters the inductor’s ripple current and stores energy to satisfy the load current when the LT1934 is quiescent.
PAGE 11
LT1934/LT1934-1 APPLICATIONS INFORMATION when used with ceramic capacitors will be lower and may be acceptable. A ﬁnal precaution regarding ceramic capacitors concerns the maximum input voltage rating of the LT1934. A ceramic input capacitor combined with trace or cable inductance forms a high quality (under damped) tank circuit. If the LT1934 circuit is plugged into a live supply, the input voltage can ring to twice its nominal value, possibly exceeding the LT1934’s rating.
PAGE 12
LT1934/LT1934-1 APPLICATIONS INFORMATION Minimum Input Voltage VOUT = 3.3V 6.0 INPUT VOLTAGE (V) LT1934 VOUT = 3.3V 5.5 TA = 25°C BOOST DIODE TIED TO OUTPUT 5.0 VIN TO START 4.5 4.0 VIN TO RUN 3.5 3.0 0.1 to VIN), then the LT1934’s internal circuitry will pull its quiescent current through its SW pin. This is ﬁne if your system can tolerate a few mA in this state. If you ground the SHDN pin, the SW pin current will drop to essentially zero.
PAGE 13
LT1934/LT1934-1 APPLICATIONS INFORMATION VIN VIN SW GND SW GND (5a) (5b) IC1 VSW VIN C2 L1 SW D1 GND C1 1934 F05 (5c) Figure 5. Subtracting the Current When the Switch is On (a) from the Current When the Switch is Off (b) Reveals the Path of the High Frequency Switching Current (c). Keep This Loop Small. The Voltage on the SW and BOOST Nodes Will Also be Switched; Keep These Nodes as Small as Possible.
PAGE 14
LT1934/LT1934-1 APPLICATIONS INFORMATION Figure 7 shows the waveforms that result when an LT1934 circuit is connected to a 24V supply through six feet of 24-gauge twisted pair. The ﬁrst plot is the response with a 2.2μF ceramic capacitor at the input. The input voltage rings as high as 35V and the input current peaks at 20A. One method of damping the tank circuit is to add another capacitor with a series resistor to the circuit. In Figure 7b an aluminum electrolytic capacitor has been added.
PAGE 15
LT1934/LT1934-1 APPLICATIONS INFORMATION in series with the input to eliminate the voltage overshoot (it also reduces the peak input current). A 0.1μF capacitor improves high frequency ﬁltering. This solution is smaller and less expensive than the electrolytic capacitor. For high input voltages its impact on efﬁciency is minor, reducing efﬁciency less than one half percent for a 5V output at full load operating from 24V. Voltage overshoot gets worse with reduced input capacitance.
PAGE 16
LT1934/LT1934-1 TYPICAL APPLICATIONS 3.3V Step-Down Converter D2 0.1μF BOOST VIN 4.5V TO 34V D1 LT1934-1 SHDN ON OFF VOUT 3.3V 45mA SW VIN C2 1μF L1 100μH 10pF 1M + FB C1 22μF 604k GND C1: TAIYO YUDEN JMK316BJ226ML C2: TAIYO YUDEN GMK316BJ105ML D1: ZETEX ZHCS400 OR ON SEMI MBR0540 D2: CENTRAL CMDSH-3 L1: COILCRAFT DO1608C-104 OR WURTH ELECTRONICS WE-PD4 TYPE S 1934 TA04 5V Step-Down Converter D2 0.1μF BOOST VIN 6.
PAGE 17
LT1934/LT1934-1 TYPICAL APPLICATIONS 1.8V Step-Down Converter D2 0.1μF BOOST VIN 3.6V TO 16V VIN C2 2.2μF VOUT 1.8V 250mA SW D1 LT1934 147k SHDN ON OFF L1 33μH + FB C1 100μF 332k GND C1: SANYO 2R5TPB100M C2: TAIYO YUDEN EMK316BJ225ML D1: ZETEX ZHCS400 OR ON SEMI MBR0540 D2: CENTRAL CMPD914 L1: SUMIDA CR43-330 1934 TA06 Loop Powered 3.3V Supply with Additional Isolated Output D3 L1B 50μH • SW VIN D4 10V 390k GND • D1 LT1934-1 SHDN 1μF D2 C1 L1A 50μH BOOST VIN 14V TO 32V <3.
PAGE 18
LT1934/LT1934-1 TYPICAL APPLICATIONS Standalone 350mA Li-Ion Battery Charger D2 0.1μF L1 47μH BOOST D3 VIN 7V TO 28V VIN SHDN CHRG GATE 0.022μF LTC4052 FB 332k 0.047μF VIN D1 1M GND + 10k SW LT1934 C2 1μF 1k 1k + ACPR SENSE TIMER GND BAT C1 47μF CTIMER 0.1μF C5 10μF C1: SANYO 6TPB47M C2: TAIYO YUDEN GMK316BJ105ML D1, D3: ON SEMICONDUCTOR MBR0540 D2: CENTRAL CMDSH-3 L1: SUMIDA CR43-470 (619) 661-6835 (408) 573-4150 (602) 244-6600 (516) 435-1110 (847) 956-0667 350mA 1-CELL 4.
PAGE 19
LT1934/LT1934-1 PACKAGE DESCRIPTION S6 Package 6-Lead Plastic TSOT-23 (Reference LTC DWG # 05-08-1636) 0.62 MAX 2.90 BSC (NOTE 4) 0.95 REF 1.22 REF 2.80 BSC 1.4 MIN 3.85 MAX 2.62 REF 1.50 – 1.75 (NOTE 4) PIN ONE ID RECOMMENDED SOLDER PAD LAYOUT PER IPC CALCULATOR 0.30 – 0.45 6 PLCS (NOTE 3) 0.95 BSC 0.80 – 0.90 0.20 BSC 0.01 – 0.10 1.00 MAX DATUM ‘A’ 0.30 – 0.50 REF 1.90 BSC 0.09 – 0.20 (NOTE 3) NOTE: 1. DIMENSIONS ARE IN MILLIMETERS 2. DRAWING NOT TO SCALE 3.
PAGE 20
LT1934/LT1934-1 TYPICAL APPLICATION 5V Step-Down Converter D2 0.1μF BOOST VIN 6.5V TO 34V D1 LT1934 SHDN ON OFF VOUT 5V 250mA SW VIN C2 2.2μF L1 68μH 10pF 1M + FB C1 68μF 332k GND C1: SANYO 6TPB68M C2: TAIYO YUDEN GMK325BJ225MN D1: ZETEX ZHCS400 OR ON SEMI MBR0540 D2: CENTRAL CMPD914 L1: SUMIDA CDRH5D28-680 1934 TA03 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1616 25V, 500mA (IOUT), 1.4MHz, High Efﬁciency Step-Down DC/DC Converter VIN = 3.6V to 25V, VOUT = 1.25V, IQ = 1.