Datasheet

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LTC3630A

3630afa

For more information www.linear.com/LTC3630A

Typical applicaTion

FeaTures DescripTion

High Efficiency, 76V

500mA Synchronous

Step-Down Converter

The LTC

3630A is a high efficiency step-down DC/DC

converter with internal high side and synchronous power

switches that draws only 12μA typical DC supply current

while maintaining a regulated output voltage at no load.

The LTC3630A can supply up to 500mA load current and

features a programmable peak current limit that provides

a simple method for optimizing efficiency and for reduc

ing output ripple and component size. The LTC3630A’s

combination

of Burst Mode

operation, integrated power

switches, low quiescent current, and programmable peak

current limit provides high efficiency over a broad range

of load currents.

With its wide input range of 4V to 76V, the LTC3630A is

a robust converter suited for regulating a wide variety of

power sources. A feedback comparator output enables

multiple LTC3630As to be paralleled in higher current

applications.

The LTC3630A is available in the thermally-enhanced

3mm × 5mm DFN and the MSE16 packages.

PARAMETER LTC3630A LTC3630

Maximum Operating V

76V 65V

Absolute Maximum V

80V 70V

Efficiency and Power Loss vs Load Current

12.5V to 76V Input to 12V Output, 500mA Step-Down Converter

applicaTions

Wide Operating Input Voltage Range: 4V to 76V

Synchronous Operation for Highest Efficiency

Internal High Side and Low Side Power MOSFETs

No Compensation Required

Adjustable 50mA to 500mA Maximum Output Current

Low Dropout Operation: 100% Duty Cycle

Low Quiescent Current: 12µA

Wide Output Range: 0.8V to V

0.8V ±1% Feedback Voltage Reference

Precise RUN Pin Threshold

Internal and External Soft-Start

Programmable 1.8V, 3.3V, 5V or Adjustable Output

Few External Components Required

Low Profile (0.75mm) 3mm × 5mm DFN and

Thermally-Enhanced MSE16 Packages

Industrial Control Supplies

Medical Devices

Portable Instruments

Automotive

Avionics

L, LT, LTC, LT M , Burst Mode, Linear Technology and the Linear logo are registered trademarks

and ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the

property of their respective owners.

22µH

RUN

22µF

OUT

12V

500mA

200k

2.2µF

12.5V TO 76V

FBO

OVLO

SET

PRG1

PRG2

GND

LTC3630A

147k

3630a TA01a

LOAD CURRENT (mA)

EFFICIENCY (%)

100

0.1 10 100 1000

3630a TA01b

OUT

= 12V

= 24V

= 76V

POWER LOSS (mW)

100

1000

EFFICIENCY

POWER LOSS

Summary of content (26 pages)

PAGE 1
LTC3630A High Efficiency, 76V 500mA Synchronous Step-Down Converter Features n n n n n n n n n n n n n n Description Wide Operating Input Voltage Range: 4V to 76V Synchronous Operation for Highest Efficiency Internal High Side and Low Side Power MOSFETs No Compensation Required Adjustable 50mA to 500mA Maximum Output Current Low Dropout Operation: 100% Duty Cycle Low Quiescent Current: 12µA Wide Output Range: 0.8V to VIN 0.
PAGE 2
LTC3630A Absolute Maximum Ratings (Note 1) VIN Supply Voltage...................................... –0.3V to 80V RUN Voltage................................................. –0.3V to 6V SS, FBO, ISET Voltages.................................. –0.3V to 6V VFB, VPRG1, VPRG2 Voltages.......................... –0.3V to 6V Operating Junction Temperature Range (Notes 2, 3, 4) LTC3630AE, LTC3630AI..................... –40°C to 125°C LTC3630AH........................................ –40°C to 150°C LTC3630AMP....
PAGE 3
LTC3630A 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). VIN = 12V, unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS 4 76 V 0.8 VIN V 3.85 3.
PAGE 4
LTC3630A Electrical Characteristics Note that the maximum ambient temperature consistent with these specifications is determined by specific operating conditions in conjunction with board layout, the rated package thermal impedance and other environmental factors. Note 4: This IC includes over temperature protection that is intended to protect the device during momentary overload conditions. The maximum rated junction temperature will be exceeded when this protection is active.
PAGE 5
LTC3630A Typical Performance Characteristics Efficiency vs Input Voltage 95 Line Regulation vs Input Voltage 0.05 VOUT = 5V FIGURE 13 CIRCUIT 90 75 70 ILOAD = 500mA ILOAD = 100mA ILOAD = 10mA ILOAD = 1mA 60 20 10 0.02 0.01 0 –0.01 –0.02 30 50 60 40 INPUT VOLTAGE (V) –0.05 70 4.97 15 5 35 45 55 25 INPUT VOLTAGE (V) 65 0.798 125 155 5.5 5.3 5.2 5.1 5.0 4.9 4.8 4.7 4.6 4.
PAGE 6
LTC3630A Typical Performance Characteristics Quiescent VIN Supply Current vs Temperature Switch On-Resistance vs Temperature 1.6 2.0 VIN = 12V 1.8 SLEEP 12 8 SHUTDOWN 4 1.6 1.4 1.2 TOP 1.0 0.8 BOTTOM 0.6 0.4 –25 65 5 95 35 TEMPERATURE (°C) 125 0 155 0 10 20 30 40 50 60 INPUT VOLTAGE (V) 3630a G16 VIN = 65V 10 8 6 SW = 65V 2 0 –2 SW = 0V –4 –6 –55 –25 95 65 35 TEMPERATURE (°C) 5 125 155 3630a G19 6 BOTTOM 0.6 0.
PAGE 7
LTC3630A Pin Functions SW (Pin 1): Switch Node Connection to Inductor. This pin connects to the drains of the internal power MOSFET switches. NC (Pins 2, 4, 13, 15 DHC Package Only): No Internal Connection. Leave these pins open. VIN (Pin 3): Main Input Supply Pin. A ceramic bypass capacitor should be tied between this pin and GND. RUN (Pin 5): Run Control Input. A voltage on this pin above 1.21V enables normal operation. Forcing this pin below 0.
PAGE 8
LTC3630A Block Diagram 1.3V 11 ACTIVE: 5µA SLEEP: 1µA ISET VIN 3 CIN PEAK CURRENT COMPARATOR + 5V – SLEEP, ACTIVE: 2µA SHUTDOWN: 0µA 2M 5 VIN + RUN + 1.21V LOGIC AND SHOOTTHROUGH PREVENTION – SW L1 VOUT 1 COUT GND 16 + – 5V REVERSE CURRENT COMPARATOR 20µA 12 FEEDBACK COMPARATOR FBO + + – 70Ω 14 8 17 VOLTAGE REFERENCE START-UP: 50µA NORMAL: 5µA 0.800V R1 R2 GND GND 5V VPRG2 VPRG1 GND GND SS SS GND SS GND SS VOUT ADJUSTABLE 5V FIXED 3.3V FIXED 1.
PAGE 9
LTC3630A Operation (Refer to Block Diagram) The LTC3630A is a synchronous step-down DC/DC converter with internal power switches that uses Burst Mode control. The low quiescent current and high switching frequency results in high efficiency across a wide range of load currents.
PAGE 10
LTC3630A Operation (Refer to Block Diagram) supply droop is desired, a capacitor can be placed from the SS pin to ground. The 5µA current that is sourced out of this pin will create a smooth voltage ramp on the capacitor. If this ramp rate is slower than the internal 0.8ms soft-start, then the output voltage will be limited by the ramp rate on the SS pin instead. The internal and external soft-start functions are reset on start-up and after an undervoltage event on the input supply.
PAGE 11
LTC3630A Applications Information The basic LTC3630A application circuit is shown on the front page of the data sheet. External component selection is determined by the maximum load current requirement and begins with the selection of the peak current programming resistor, RISET. The inductor value L can then be determined, followed by capacitors CIN and COUT. Peak Current Resistor Selection The peak current comparator has a guaranteed maximum current limit of 1A (1.
PAGE 12
LTC3630A Applications Information VOUT = 3.3V ISET OPEN L = 4.2µH 500 400 300 L = 10µH 200 L = 22µH 100 0 10 20 30 40 100 L = 100µH L = 47µH 0 1000 INDUCTOR VALUE (µH) SWITCHING FREQUENCY (kHz) 600 50 60 10 100 70 VIN INPUT VOLTAGE (V) 1000 PEAK INDUCTOR CURRENT (mA) 3630a F03 Figure 3. Switching Frequency for VOUT = 3.3V well-controlled, the inductor value must be chosen so that it is larger than a minimum value which can be computed as follows: L> VIN(MAX) • tON(MIN) • 1.
PAGE 13
LTC3630A Applications Information CIN and COUT Selection The input capacitor, CIN, is needed to filter the trapezoidal current at the source of the top high side MOSFET. CIN should be sized to provide the energy required to charge the inductor without causing a large decrease in input voltage (∆VIN).
PAGE 14
LTC3630A Applications Information Ceramic Capacitors and Audible Noise Higher value, lower cost ceramic capacitors are now becoming available in smaller case sizes. Their high ripple current, high voltage rating, and low ESR make them ideal for switching regulator applications. However, care must be taken when these capacitors are used at the input and output.
PAGE 15
LTC3630A Applications Information application circuit. To keep the variation of the rising VIN UVLO threshold to less than 5% due to the internal pullup circuitry, the following equations should be used to calculate R3 and R4: VOUT LTC3630A VFB R1 5V 4.2M R2 0.8V 800k SS VPRG1 VPRG2 3630a F07 Figure 7. Setting the Output Voltage with External and Internal Resistors RUN Pin and External Input Undervoltage Lockout The RUN pin has two different threshold voltage levels. Pulling the RUN pin below 0.
PAGE 16
LTC3630A Applications Information Note that the soft-start capacitor may not be the limiting factor in the output voltage ramp. The maximum output current, which is equal to half the peak current, must charge the output capacitor from 0V to its regulated value. For small peak currents or large output capacitors, this ramp time can be significant.
PAGE 17
LTC3630A Applications Information The gate charge current results from switching the gate capacitance of the internal power MOSFET switches. Each time the gate is switched from high to low to high again, a packet of charge, ∆Q, moves from VIN to ground. The resulting ∆Q/dt is the current out of VIN that is typically larger than the DC bias current. 2. I2R losses are calculated from the resistances of the internal switches, RSW and external inductor RL.
PAGE 18
LTC3630A Applications Information Next, verify that this value meets the LMIN requirement. For this input voltage and peak current, the minimum inductor value is: 24V • 150ns ≅ 3µH 1.2A LMIN = Therefore, the minimum inductor requirement is satisfied and the 10μH inductor value may be used. Next, CIN and COUT are selected. For this design, CIN should be sized for a current rating of at least: IRMS = 500mA • 3.3V 24V • – 1 ≅ 175mARMS 24V 3.
PAGE 19
LTC3630A Applications Information PC Board Layout Checklist When laying out the printed circuit board, the following checklist should be used to ensure proper operation of the LTC3630A. Check the following in your layout: 1. Large switched currents flow in the power switches and input capacitor. The loop formed by these components should be as small as possible. A ground plane is recommended to minimize ground impedance. 2.
PAGE 20
LTC3630A Applications Information Pin Clearance/Creepage Considerations The LTC3630A is available in two packages (MSE16 and DHC) both with identical functionality. However, the 0.2mm (minimum space) between pins and paddle on the DHCpackage may not provide sufficient PC board trace clearance between high and low voltage pins in some higher voltage applications. In applications where clearance is required, the MSE16 package should be used.
PAGE 21
LTC3630A Typical Applications 4V to 24V Input to 3.3V Output, 250mA Regulator with External Soft-Start, Small Size COUT 10µF CSS 100nF GND RISET 100k VIN = 12V 90 VOUT 3.3V 250mA EFFICIENCY 80 3630a TA02a 1000 70 60 100 50 10 40 30 POWER LOSS POWER LOSS (mW) CIN 2.
PAGE 22
LTC3630A Typical Applications 5V to 76V Input to 5V Output,150mA Regulator with 20kHz Minimum Burst Frequency L1 33µH CIN 2.2µF VIN SW RUN RISET 60.4k COUT 10µF LTC3630A VFB 30.
PAGE 23
LTC3630A Package Description Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. MSE Package Variation: MSE16 (12) 16-Lead Plastic MSOP with 4 Pins Removed Exposed Die Pad (Reference LTC DWG # 05-08-1871 Rev D) BOTTOM VIEW OF EXPOSED PAD OPTION 2.845 ±0.102 (.112 ±.004) 5.10 (.201) MIN 2.845 ±0.102 (.112 ±.004) 0.889 ±0.127 (.035 ±.005) 8 1 1.651 ±0.102 (.065 ±.004) 1.651 ±0.102 3.20 – 3.45 (.065 ±.004) (.126 – .136) 16 0.305 ±0.038 (.0120 ±.
PAGE 24
LTC3630A Package Description Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. DHC Package 16-Lead Plastic DFN (5mm × 3mm) (Reference LTC DWG # 05-08-1706 Rev Ø) 0.65 ±0.05 3.50 ±0.05 1.65 ±0.05 2.20 ±0.05 (2 SIDES) PACKAGE OUTLINE 0.25 ± 0.05 0.50 BSC 4.40 ±0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 5.00 ±0.10 (2 SIDES) R = 0.20 TYP 3.00 ±0.10 (2 SIDES) 9 R = 0.115 TYP 0.40 ±0.10 16 1.65 ±0.
PAGE 25
LTC3630A Revision History REV DATE DESCRIPTION A 8/13 Removed RUN pin connection from VIN on schematic. PAGE NUMBER 1 3630afa 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 representation that the interconnection of its information circuits as described herein will not infringe on existing patent rights. For more www.linear.
PAGE 26
LTC3630A Typical Application 4V to 76V Input to 3.3V Output, 500mA Step-Down Converter VIN 4V TO 76V L1 10µH CIN 2.2µF VIN SW COUT 47µF LTC3630A RUN VFB SS VPRG1 VPRG2 FBO ISET GND VOUT 3.3V 500mA 3630a TA06 CIN: TDK CGA6N3X7R2A225K COUT: MURATA GCM32ER70J476KE19L L1: COILCRAFT MSS1038T-103 Related Parts PART NUMBER DESCRIPTION COMMENTS LTC3630 65V 500mA Synchronous Step-Down DC/DC Converter VIN: 4V to 65V, VOUT(MIN) = 0.