Datasheet

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BST

SEN

GND

RTN

/SD

LM34910C

www.ti.com

SNVS517B –MAY 2007–REVISED MARCH 2013

LM34910C High Voltage (50V, 1.25A) Step Down Switching Regulator

Check for Samples: LM34910C

FEATURES

DESCRIPTION

The LM34910C Step Down Switching Regulator

• Integrated 55V, N-Channel Buck Switch

features all of the functions needed to implement a

• Integrated Start-Up Regulator

low cost, efficient, buck bias regulator capable of

• Input Voltage Range: 8V to 50V

supplying 1.25A to the load. This buck regulator

contains a 55V N-Channel Buck Switch, and is

• No Loop Compensation Required

available in the thermally enhanced WSON-10

• Ultra-Fast Transient Response

package. The hysteretic regulation scheme requires

• Operating Frequency Remains Constant with

no loop compensation, results in fast load transient

Load Current and Input Voltage

response, and simplifies circuit implementation. The

operating frequency remains constant with line and

• Maximum Duty Cycle Limited During Start-Up

load variations due to the inverse relationship

• Adjustable Output Voltage

between the input voltage and the on-time. The

• Valley Current Limit At 1.25A

current limit detection is set at 1.25A. Additional

features include: VCC under-voltage lockout, thermal

• Precision Internal Reference

shutdown, gate drive under-voltage lockout, and

• Low Bias Current

maximum duty cycle limiter.

• Highly Efficient Operation

• Thermal Shutdown

Package

• WSON-10 (4 mm x 4 mm)

TYPICAL APPLICATIONS

• Exposed Thermal Pad For Improved Heat

Dissipation

• High Efficiency Point-Of-Load (POL) Regulator

• Non-Isolated Telecommunication Buck

Regulator

• Secondary High Voltage Post Regulator

Connection Diagram

10-Lead WSON

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of

Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

2All trademarks are the property of their respective owners.

PRODUCTION DATA information is current as of publication date.

Products conform to specifications per the terms of the Texas

Instruments standard warranty. Production processing does not

necessarily include testing of all parameters.

Summary of content (19 pages)

PAGE 1
LM34910C www.ti.com SNVS517B – MAY 2007 – REVISED MARCH 2013 LM34910C High Voltage (50V, 1.25A) Step Down Switching Regulator Check for Samples: LM34910C FEATURES DESCRIPTION • • • • • • The LM34910C Step Down Switching Regulator features all of the functions needed to implement a low cost, efficient, buck bias regulator capable of supplying 1.25A to the load. This buck regulator contains a 55V N-Channel Buck Switch, and is available in the thermally enhanced WSON-10 package.
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LM34910C SNVS517B – MAY 2007 – REVISED MARCH 2013 www.ti.com Typical Application Circuit and Block Diagram 7V SERIES REGULATOR 8V-50V Input LM34910C 10 VIN VCC 9 C3 VCC UVLO C5 THERMAL SHUTDOWN C1 RON RON/ 8 SD 280 ns OFF TIMER ON TIMER RON START COMPLETE + 0.7V START COMPLETE BST 2 GATE DRIVE UVLO C4 VIN 2.5V 11.5 PA DRIVER LOGIC 7 SS C6 DRIVER L1 LEVEL SHIFT SW 1 VOUT1 6 FB + REGULATION COMPARATOR + OVER2.875V VOLTAGE COMPARATOR 5 RTN D1 CURRENT LIMIT COMPARATOR + 62.
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LM34910C www.ti.com SNVS517B – MAY 2007 – REVISED MARCH 2013 Absolute Maximum Ratings (1) (2) VIN to GND 55V BST to GND 70V SW to GND (Steady State) -1.5V ESD Rating (3) Human Body Model 2kV BST to VCC 55V VIN to SW 55V BST to SW 14V VCC to GND 14V SGND to RTN -0.3V to +0.3V Current out of ISEN See Text SS to RTN -0.3V to 4V All Other Inputs to GND -0.
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LM34910C SNVS517B – MAY 2007 – REVISED MARCH 2013 www.ti.com Electrical Characteristics (continued) Specifications with standard typeface are for TJ = 25°C, and those with boldface type apply over full Operating Junction Temperature range. VIN = 24V, RON = 200k unless otherwise stated(1). Symbol Parameter Conditions Min Typ Max Units Softstart Pin Pull-up voltage 2.5 V Internal current source 11.5 µA Current Limit ILIM Threshold Current out of ISEN 1 1.25 1.
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LM34910C www.ti.com SNVS517B – MAY 2007 – REVISED MARCH 2013 Typical Performance Characteristics 7.5 7.0 kH = 19 4 6.5 S FS = 730 kHz F VCC (V) z FS = 100 kHz 6.0 5.5 Load Current = 500 mA 5.0 6.5 7.0 7.5 8.0 8.5 9.0 VIN (V) Figure 1. VCC vs VIN Figure 2.
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LM34910C SNVS517B – MAY 2007 – REVISED MARCH 2013 www.ti.com Functional Description The LM34910C Step Down Switching Regulator features all the functions needed to implement a low cost, efficient buck bias power converter capable of supplying 1.25A to the load. This high voltage regulator contains a 55V N-Channel buck switch, is easy to implement, and is available in the thermally enhanced WSON-10 package.
PAGE 7
LM34910C www.ti.com SNVS517B – MAY 2007 – REVISED MARCH 2013 Output voltage regulation is based on ripple voltage at the feedback input, requiring a minimum amount of ESR for the output capacitor C2. The LM34910C requires a minimum of 25 mV of ripple voltage at the FB pin. In cases where the capacitor’s ESR is insufficient additional series resistance may be required (R3 in Typical Application Circuit and Block Diagram).
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LM34910C SNVS517B – MAY 2007 – REVISED MARCH 2013 www.ti.com Regulation Comparator The feedback voltage at FB is compared to the voltage at the Softstart pin (2.5V). In normal operation (the output voltage is regulated), an on-time period is initiated when the voltage at FB falls below 2.5V. The buck switch stays on for the on-time, causing the FB voltage to rise above 2.5V. After the on-time period, the buck switch stays off until the FB voltage falls below 2.5V.
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LM34910C www.ti.com SNVS517B – MAY 2007 – REVISED MARCH 2013 Figure 6 illustrates the inductor current waveform. During normal operation the load current is Io, the average of the ripple waveform. When the load resistance decreases the current ratchets up until the lower peak reaches 1.25A. During the Current Limited portion of Figure 6, the current ramps down to 1.25A during each off-time, initiating the next on-time (assuming the voltage at FB is <2.5V).
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LM34910C SNVS517B – MAY 2007 – REVISED MARCH 2013 www.ti.com APPLICATIONS INFORMATION EXTERNAL COMPONENTS The following guidelines can be used to select the external components. R1 and R2: The ratio of these resistors is calculated from: R1/R2 = (VOUT/2.5V) - 1 (8) R1 and R2 should be chosen from standard value resistors in the range of 1.0 kΩ - 10 kΩ which satisfy the above ratio. RON: The minimum value for RON is calculated from: 200 ns x VINMAX RON t 1.
PAGE 11
LM34910C www.ti.com SNVS517B – MAY 2007 – REVISED MARCH 2013 C2, and R3: Since the LM34910C requires a minimum of 25 mVp-p of ripple at the FB pin for proper operation, the required ripple at VOUT1 is increased by R1 and R2. This necessary ripple is created by the inductor ripple current acting on C2’s ESR + R3. The minimum ripple current is calculated using Equation 11, rearranged to solve for IOR at minimum VIN.
PAGE 12
LM34910C SNVS517B – MAY 2007 – REVISED MARCH 2013 www.ti.com PC BOARD LAYOUT The LM34910C regulation, over-voltage, and current limit comparators are very fast, and respond to short duration noise pulses. Layout considerations are therefore critical for optimum performance. The layout must be as neat and compact as possible, and all of the components must be as close as possible to their associated pins. The current loop formed by D1, L1, C2 and the SGND and ISEN pins should be as small as possible.
PAGE 13
LM34910C www.ti.com SNVS517B – MAY 2007 – REVISED MARCH 2013 REVISION HISTORY Changes from Revision A (March 2013) to Revision B • Page Changed layout of National Data Sheet to TI format ..........................................................................................................
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PACKAGE OPTION ADDENDUM www.ti.
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PACKAGE OPTION ADDENDUM www.ti.com 14-Feb-2014 continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
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PACKAGE MATERIALS INFORMATION www.ti.com 11-Oct-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing LM34910CSD/NOPB WSON DPR 10 LM34910CSDE/NOPB WSON DPR LM34910CSDX/NOPB WSON DPR SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant 1000 178.0 12.4 4.3 4.3 1.3 8.0 12.0 Q1 10 250 178.0 12.4 4.3 4.3 1.3 8.0 12.0 Q1 10 4500 330.0 12.4 4.3 4.3 1.3 8.0 12.
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PACKAGE MATERIALS INFORMATION www.ti.com 11-Oct-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM34910CSD/NOPB WSON DPR 10 1000 210.0 185.0 35.0 LM34910CSDE/NOPB WSON DPR 10 250 210.0 185.0 35.0 LM34910CSDX/NOPB WSON DPR 10 4500 367.0 367.0 35.
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MECHANICAL DATA DPR0010A SDC10A (Rev A) www.ti.
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