Datasheet

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VIN

BST

LM34919

VCC

RON/SD

8V - 40V

Input

OUT

RTN

ISEN

SGND

SHUTDOWN

LM34919

www.ti.com

SNOSAY2E –MAY 2007–REVISED FEBRUARY 2013

Ultra-Small 40-V 600-mA Constant On-Time Buck Switching Regulator

Check for Samples: LM34919

FEATURES

• Integrated N-Channel buck switch

• Precision internal reference

• Integrated start-up regulator • Low bias current

• Input Voltage Range: 8V to 40V • Highly efficient operation

• No loop compensation required • Thermal shutdown

• Ultra-Fast transient response • 10-Pin DSBGA Package

• Operating frequency remains constant with

APPLICATIONS

load current and input voltage

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

• Maximum switching frequency: 2.0 MHz

• Non-Isolated Telecommunication Buck

• Maximum Duty Cycle Limited During Start-Up

Regulator

• Adjustable output voltage

• Secondary High Voltage Post Regulator

• Valley Current Limit At 0.64A

DESCRIPTION

The LM34919 Step Down Switching Regulator features all of the functions needed to implement a low cost,

efficient, buck bias regulator capable of supplying 0.6A to the load. This buck regulator contains an N-Channel

Buck Switch, and is available in a 10-pin DSBGA package. The constant on-time feedback regulation scheme

requires no loop compensation, results in fast load transient response, and simplifies circuit implementation. The

operating frequency remains constant with line and load variations due to the inverse relationship between the

input voltage and the on-time. The valley current limit results in a smooth transition from constant voltage to

constant current mode when current limit is detected, reducing the frequency and output voltage, without the use

of foldback. Additional features include: VCC under-voltage lockout, thermal shutdown, gate drive under-voltage

lockout, and maximum duty cycle limiter.

Basic Step Down Regulator

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 (21 pages)

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LM34919 www.ti.com SNOSAY2E – MAY 2007 – REVISED FEBRUARY 2013 Ultra-Small 40-V 600-mA Constant On-Time Buck Switching Regulator Check for Samples: LM34919 FEATURES 1 • • • • • • 2 • • • • Integrated N-Channel buck switch Integrated start-up regulator Input Voltage Range: 8V to 40V No loop compensation required Ultra-Fast transient response Operating frequency remains constant with load current and input voltage Maximum switching frequency: 2.
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LM34919 SNOSAY2E – MAY 2007 – REVISED FEBRUARY 2013 www.ti.com Connection Diagram SW D3 BST C1 C3 VCC C3 C1 SGND B1 B3 SS B3 B1 RON/SD A1 A3 FB A3 VIN D1 ISEN D2 A2 D3 D2 A2 D1 A1 RTN Figure 1. Bump Side Figure 2. Top View PIN DESCRIPTIONS 2 Pin No. Name A1 RON/SD A2 RTN A3 FB B1 SGND B3 SS C1 Description Application Information On-time control and shutdown An external resistor from VIN to this pin sets the buck switch on-time.
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LM34919 www.ti.com SNOSAY2E – MAY 2007 – REVISED FEBRUARY 2013 These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates. Absolute Maximum Ratings (1) VIN to RTN 44V BST to RTN 52V SW to RTN (Steady State) -1.5V ESD Rating, Human Body Model (2) 2kV BST to VCC 44V VIN to SW 44V BST to SW 14V VCC to RTN 14V SGND to RTN -0.3V to +0.
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LM34919 SNOSAY2E – MAY 2007 – REVISED FEBRUARY 2013 www.ti.com Electrical Characteristics Specifications with standard type are for TJ = 25°C only; limits in boldface type apply over the full Operating Junction Temperature (TJ) range. Minimum and Maximum limits are specified through test, design, or statistical correlation. Typical values represent the most likely parametric norm at TJ = 25°C, and are provided for reference purposes only.
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LM34919 www.ti.com SNOSAY2E – MAY 2007 – REVISED FEBRUARY 2013 Typical Performance Characteristics Efficiency at 800 kHz Efficiency at 2 MHz Figure 3. Figure 4. VCC vs VIN VCC vs ICC 8 7.5 7 IOUT = 0 mA, All frequencies VIN VIN = 9V 6 8 10V VIN = 8V 5 6.5 VCC (V) VCC (V) 7.0 650 kHz, IOUT = 200 mA 6.0 3 2 1.3 MHz, 5.5 4 IOUT = 200 mA VCC Externally Loaded 1 FS = 800 kHz 5.0 6.5 0 7.0 7.5 8.0 8.5 9.0 0 2 4 6 8 10 12 ICC (mA) VIN (V) Figure 5. Figure 6.
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LM34919 SNOSAY2E – MAY 2007 – REVISED FEBRUARY 2013 www.ti.com Typical Performance Characteristics (continued) Voltage at the RON/SD Pin Shutdown and Operating Current into VIN Figure 9. Figure 10. TYPICAL APPLICATION CIRCUIT AND BLOCK DIAGRAM 7V SERIES REGULATOR 8V-40V Input LM34919 VIN VCC C3 VCC UVLO C5 C1 + RON RON/SD ON TIMER RON START COMPLETE OFF TIMER 0.8V START COMPLETE BST GATE DRIVE UVLO C4 VIN 2.5V 10.
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LM34919 www.ti.com SNOSAY2E – MAY 2007 – REVISED FEBRUARY 2013 VIN 7.0V UVLO VCC SW Pin Inductor Current 2.5V SS Pin VOUT t1 t2 Figure 11. Start Up Sequence FUNCTIONAL DESCRIPTION The LM34919 Step Down Switching Regulator features all the functions needed to implement a low cost, efficient buck bias power converter capable of supplying at least 0.6A to the load. This high voltage regulator contains an N-Channel buck switch, is easy to implement, and is available in a DSBGA package.
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LM34919 SNOSAY2E – MAY 2007 – REVISED FEBRUARY 2013 www.ti.com Control Circuit Overview The LM34919 buck DC-DC regulator employs a control scheme based on a comparator and a one-shot on-timer, with the output voltage feedback (FB) compared to an internal reference (2.5V). If the FB voltage is below the reference the buck switch is turned on for a time period determined by the input voltage and a programming resistor (RON).
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LM34919 www.ti.com SNOSAY2E – MAY 2007 – REVISED FEBRUARY 2013 VCC C3 BST C4 L1 LM34919 D2 SW VOUT D1 ISEN R1 R3 SGND R2 C2 FB Figure 12. Self Biased Configuration 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 programmed on-time, causing the FB voltage to rise above 2.5V.
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LM34919 SNOSAY2E – MAY 2007 – REVISED FEBRUARY 2013 www.ti.com VIN Input Voltage RON LM34919 RON/SD STOP RUN Figure 13. Shutdown Implementation Current Limit Current limit detection occurs during the off-time by monitoring the recirculating current through the free-wheeling diode (D1). Referring to the Block Diagram, when the buck switch is turned off the inductor current flows through the load, into SGND, through the sense resistor, out of ISEN and through D1. If that current exceeds 0.
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LM34919 www.ti.com SNOSAY2E – MAY 2007 – REVISED FEBRUARY 2013 N-Channel Buck Switch and Driver The LM34919 integrates an N-Channel buck switch and associated floating high voltage gate driver. The peak current allowed through the buck switch is 1.5A, and the maximum allowed average current is 1A. The gate driver circuit works in conjunction with an external bootstrap capacitor and an internal high voltage diode. A 0.
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LM34919 SNOSAY2E – MAY 2007 – REVISED FEBRUARY 2013 www.ti.com L1: The main parameter affected by the inductor is the inductor current ripple amplitude (IOR). The minimum load current is used to determine the maximum allowable ripple in order to maintain continuous conduction mode, where the lower peak does not reach 0 mA. This is not a requirement of the LM34919, but serves as a guideline for selecting L1.
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LM34919 www.ti.com C6 = SNOSAY2E – MAY 2007 – REVISED FEBRUARY 2013 t2 x 10.5 PA 2.5V = 0.021 PF (15) D1: A Schottky diode is recommended. Ultra-fast recovery diodes are not recommended as the high speed transitions at the SW pin may inadvertently affect the IC's operation through external or internal EMI. The diode should be rated for the maximum input voltage, the maximum load current, and the peak current which occurs when the current limit and maximum ripple current are reached simultaneously.
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LM34919 SNOSAY2E – MAY 2007 – REVISED FEBRUARY 2013 www.ti.com a) Reduced ripple configuration: In Figure 18, Cff is added across R1 to AC-couple the ripple at VOUT directly to the FB pin. This allows the ripple at VOUT to be reduced to a minimum of 25 mVpp by reducing R3, since the ripple at VOUT is not attenuated by the feedback resistors. The minimum value for Cff is determined from: tON (max) Cff = (R1//R2) (17) where tON(max) is the maximum on-time, which occurs at VIN(min).
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LM34919 www.ti.com SNOSAY2E – MAY 2007 – REVISED FEBRUARY 2013 L1 SW LM34919 R1 R3 FB VOUT R2 C2 Figure 20. Alternate Minimum Output Ripple Configuration Minimum Load Current The LM34919 requires a minimum load current of 1 mA. If the load current falls below that level, the bootstrap capacitor (C4) may discharge during the long off-time, and the circuit will either shutdown, or cycle on and off at a low frequency.
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LM34919 SNOSAY2E – MAY 2007 – REVISED FEBRUARY 2013 www.ti.com REVISION HISTORY Changes from Revision D (February 2013) to Revision E • 16 Page Changed layout of National Data Sheet to TI format ..........................................................................................................
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PACKAGE OPTION ADDENDUM www.ti.
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PACKAGE MATERIALS INFORMATION www.ti.com 14-Mar-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) LM34919TL/NOPB DSBGA YPA 10 250 178.0 8.4 LM34919TLX/NOPB DSBGA YPA 10 3000 178.0 8.4 Pack Materials-Page 1 B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant 1.68 2.13 0.76 4.0 8.0 Q1 1.68 2.13 0.76 4.0 8.
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PACKAGE MATERIALS INFORMATION www.ti.com 14-Mar-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM34919TL/NOPB DSBGA YPA LM34919TLX/NOPB DSBGA YPA 10 250 210.0 185.0 35.0 10 3000 210.0 185.0 35.
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MECHANICAL DATA YPA0010 0.600 ±0.075 D E TLP10XXX (Rev D) D: Max = 1.992 mm, Min =1.931 mm E: Max = 1.53 mm, Min = 1.469 mm 4215069/A NOTES: A. All linear dimensions are in millimeters. Dimensioning and tolerancing per ASME Y14.5M-1994. B. This drawing is subject to change without notice. www.ti.
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