Datasheet

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LTC3824

3824fh

For more information www.linear.com/LTC3824

Typical applicaTion

FeaTures

applicaTions

DescripTion

High Voltage Step-Down

Controller With 40µA

Quiescent Current

The LT C

3824 is a step-down DC/DC controller designed

to drive an external P-channel MOSFET. With a wide input

range of 4V to 60V and a high voltage gate driver, the

LTC3824 is suitable for many industrial and automotive

high power applications. Constant frequency current mode

operation provides excellent performance.

The LTC3824 can be configured for Burst Mode operation.

Burst Mode operation enhances low current efficiency

(only 40µA quiescent current) and extends battery run

time. The switching frequency can be programmed up to

600kHz and is easily synchronizable.

Other features include current limit, soft-start, micropower

shutdown, and Burst Mode disable.

The LTC3824 is available in a 10-lead MSE power package.

5V/2A Buck Converter

Wide Input Range: 4V to 60V

Current Mode Constant Frequency PWM

Very Low Dropout Operation: 100% Duty Cycle

Programmable Switching Frequency:

200kHz to 600kHz

Selectable High Efﬁcient Burst Mode

Operation:

40µA Quiescent Current

Easy Synchronization

8V, 2A Gate Drive (V

> 10V) for Industrial High

Voltage P-Channel MOSFET

Programmable Soft-Start

Programmable Current Limit

Available in a Small 10-Pin Thermally Enhanced

MSE Package

Industrial and Automotive Power Supplies

Telecom Power Supplies

Distributed Power Systems

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

All other trademarks are the property of their respective owners. Protected by U.S. Patents

including 5731964.

Efficiency and Power Loss vs Load Current

3824 TA01

10k

80.6k

0.025Ω

51Ω

CAP

0.1µF

422k

100pF

OUT

100µF

×2

22µH

OUT

0.1µF

392k

33µF

100V

3.3nF

LTC3824

SENSE

GATE

CAP

SET

GND

SYNC/MODE

5.5V TO 60V

LOAD CURRENT (mA)

EFFICIENCY (%)

POWER LOSS (W)

10 100

3824 TA01a

100

0.5

1.0

2.0

1.5

2.5

EFFICIENCY

POWER LOSS

20001000

= 12V

= 40V

= 12V

Downloaded from Arrow.com.

Summary of content (16 pages)

PAGE 1
LTC3824 High Voltage Step-Down Controller With 40µA Quiescent Current Description Features n n n n n n n n n n Wide Input Range: 4V to 60V Current Mode Constant Frequency PWM Very Low Dropout Operation: 100% Duty Cycle Programmable Switching Frequency: 200kHz to 600kHz Selectable High Efficient Burst Mode® Operation: 40µA Quiescent Current Easy Synchronization 8V, 2A Gate Drive (VCC > 10V) for Industrial High Voltage P-Channel MOSFET Programmable Soft-Start Programmable Current Limit Available in a Sma
PAGE 2
LTC3824 Absolute Maximum Ratings Pin Configuration (Note 1) VCC ............................................................................65V SS, RSET, VFB ..............................................................4V VC ...............................................................................3V SYNC/MODE................................................................6V VCC – VSENSE ...............................................................1V Operating Junction Temperature Range (Note 2).
PAGE 3
LTC3824 electrical characteristics The l denotes the specifications which apply over the specified operating junction temperature range, otherwise specifications are at TA = 25°C (Note 2). VCC = 12V, RSET = 392k, CCAP = 0.1µF. No load on any outputs, unless otherwise specified. PARAMETER CONDITIONS Supply Voltage (VCC) Supply Current (IVCC) MIN l TYP 4 MAX UNITS 60 V 1.3 mA VC ≤ 0.4V (Switching Off), VCC ≤ 60V VSYNC = 0V (Burst Mode operation Disable) 0.
PAGE 4
LTC3824 Electrical Characteristics The l denotes the specifications which apply over the specified operating junction temperature range, otherwise specifications are at TA = 25°C (Note 2). VCC = 12V, RSET = 392k, CCAP = 0.1µF. No load on any outputs, unless otherwise specified. PARAMETER CONDITIONS MIN TYP MAX 7.9 7.9 8.8 8.
PAGE 5
LTC3824 Typical Performance Characteristics 8.5 (VCC – VCAP) vs IGATE at VDRIVE Low 3 TA = 25°C unless otherwise noted. ICC vs VCC 3 8.4 2 8.2 ΔFREQUENCY (kHz) 8.3 VCC-VCAP (V) Switching Frequency Change vs VCC at RSET = 392kΩ 2 ICC (mA) 8.1 8.0 7.9 VFB = 0.75V 1 VFB = 0.85V 1 0 –1 7.8 –2 7.7 7.6 0 20 30 IGATE (mA) 10 40 0 50 0 10 20 3824 G01 VREF Change vs VCC 30 VCC (V) 40 50 –3 60 3824 G02 Switching Frequency vs RSET 0.
PAGE 6
LTC3824 Typical Performance Characteristics TA = 25°C unless otherwise noted.
PAGE 7
LTC3824 pin functions GND (Pin 1, Exposed Pad Pin 11): Ground. Exposed pad must be soldered to PCB with expanded metal trace for rated thermal performance. SYNC/MODE (Pin 2): Synchronization Input and Burst Mode Operation Enable/Disable. If this pin is left open or pulled higher than 2V, Burst Mode operation will be enabled at light load and the typical threshold of entering Burst Mode operation is one third of current limit.
PAGE 8
LTC3824 block diagram SENSE 1.1V VCC + + SS VIN Burst Mode DISABLE – REFERENCE RS 100k VREF GATE Q1 B1 1.8V L VOUT 0.3µA 100k – M2 – 50pF + + Y1 S Q R – – + 1 2V CAP D1 + C2 RF1 COUT E1 M1 1.5V RF2 OR1 Y2 RFREQ – OSC + RSET + 0.1V – Y6 + SHUTDOWN + 50KHz FOLDBACK SYNC DISABLE 6 ++ + 0.5V SLOPE COMP 0.025V + PWM GND Y5 – + + 250k 8V + SYNC/ MODE + 2.5V CCAP 0.1µF – GM Burst Mode OPERATION CONTROL FB D6 – D7 + VREF 0.
PAGE 9
LTC3824 applications information Burst Mode Operation The LTC3824 can be configured for Burst Mode operation to enhance light load efficiency (only 40µA quiescent current) and extend battery run time by leaving the SYNC/ MODE pin open or pulling it higher than 2V. In this mode, when output load drops the loop control voltage VC also drops and when VC reaches approximately 0.9V at low duty cycle the LTC3824 goes into sleep mode with the switch turned off.
PAGE 10
LTC3824 applications information Inductor Selection The maximum inductor current is determined by : IRIPPLE 2 (V – V ) • D where IRIPPLE = IN OUT f •L +V V and Duty Cycle D = OUT D VIN + VD PMOSFET = IL(MAX) =IOUT(MAX) + (VIN– VOUT ) • D f • 0.4 •IOUT(MAX) The saturation current level of the inductor should be sufficiently larger than IL(MAX).
PAGE 11
LTC3824 Applications Information on the P-channel switch duty cycle. At high input voltages the diode conducts most of the time. As VIN approaches VOUT the diode conducts only a small fraction of the time. The worst condition for the diode is when the output is shorted to ground. Under this condition the diode must safely handle the maximum current at close to 100% of the time. Therefore, the diode must be carefully chosen to meet the worst case voltage and current requirements.
PAGE 12
LTC3824 applications information 2. Power MOSFET switching and conduction losses: PMOSFET = VOUT + VD (I )2 (1+ δ)RDS(ON) VIN + VD OUT + K(VIN )2 (IOUT )(CRSS )(f) 3. The I2R losses of the current sense resistor: P(SENSE R) = (IOUT)2 • R • D where D is the duty cycle 4. The inductor loss due to winding resistance: P(WINDING) = (IOUT)2 • RW Place the LTC3824 and associated components tightly together and next to the section with power components.
PAGE 13
LTC3824 typical application 12V 2A Buck Converter VIN 12.5V TO 60V CIN1 33µF 100V + CCAP 0.1µF CIN2 2.2µF 100V CAP VCC SYNC/MODE SENSE 100pF CIN1: SANYO 63MV68AX CIN2: TDK C4532X7R2A225M COUT: SANYO OSCON, 16SP270M, TDKC2012X7RIC105K L1: D104C919AS-330M D1: SS3H9 Q1: Si7465DP RS 0.025Ω LTC3824 RSET GATE 301k Q1 L1 33µH GND + 1000pF D1 68k SS 0.1µF 113k COUT 270µF VOUT 12V 1µF 2A 16V X7R VFB VC 8.06k 15k 3824 TA02 1000pF 3824fh For more information www.linear.
PAGE 14
LTC3824 package description Please refer to http://www.linear.com/product/LTC3824#packaging for the most recent package drawings. MSE Package 10-Lead Plastic MSOP, Exposed Die Pad (Reference LTC DWG # 05-08-1664 Rev I) BOTTOM VIEW OF EXPOSED PAD OPTION 1.88 ±0.102 (.074 ±.004) 5.10 (.201) MIN 1 0.889 ±0.127 (.035 ±.005) 1.68 ±0.102 (.066 ±.004) 0.05 REF 10 0.305 ± 0.038 (.0120 ±.0015) TYP RECOMMENDED SOLDER PAD LAYOUT 3.00 ±0.102 (.118 ±.
PAGE 15
LTC3824 Revision History (Revision history begins at Rev F) REV DATE DESCRIPTION F 12/10 E-grade Ordering Information updated to 125°C 2 EC header corrected to Operation Junction Temperature 2 Updated/corrected Note 2 3 Updated Block Diagram 7 G 3/11 PAGE NUMBER Shutdown section updated 8 Package updated 12 Related Parts updated per Marketing request 14 Updated Temperature Range for MP-grade part 2 Added LTC3824MP to Electrical Characteristics tables H 01/16 2, 3 Updated Note 2
PAGE 16
LTC3824 Typical Application 3V 2A Buck Converter VIN 4.5V TO 60V CIN1 33µF 100V CIN2 2.2µF 100V + CIN1: SANYO 63MV68AX CIN2: TDK C4532X7R2A225M COUT: SANYO OSCON, 16SP270M, TDKC2012X7RIC105K L1: D104C919AS-330M D1: SS3H9 Q1: Si7465DP Q2: 2N7002 CCAP 0.1µF CAP VCC 100pF RS 0.025Ω SYNC/MODE SENSE LTC3824 RSET GATE Q1 L1 33µH 301k GND + 100pF D1 51Ω SS 4.7MΩ* COUT 270µF VOUT 3.3V 1µF 2A 16V 255k VFB VC 80.6k Q2* 0.