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LM5118, LM5118-Q1

www.ti.com

SNVS566G –APRIL 2008–REVISED FEBRUARY 2013

Wide Voltage Range Buck-Boost Controller

Check for Samples: LM5118, LM5118-Q1

FEATURES

DESCRIPTION

The LM5118 wide voltage range Buck-Boost

• LM5118-Q1 is an Automotive Grade product

switching regulator controller features all of the

that is AEC-Q100 grade 1 qualified (-40°C to

functions necessary to implement a high

125°C operating junction temperature)

performance, cost efficient Buck-Boost regulator

• Ultra-wide input voltage range from 3V to 75V

using a minimum of external components. The Buck-

Boost topology maintains output voltage regulation

• Emulated peak current mode control

when the input voltage is either less than or greater

• Smooth transition between step-down and

than the output voltage making it especially suitable

step- up modes

for automotive applications. The LM5118 operates as

• Switching frequency programmable to 500KHz

a buck regulator while the input voltage is sufficiently

greater than the regulated output voltage and

• Oscillator synchronization capability

gradually transitions to the buck-boost mode as the

• Internal high voltage bias regulator

input voltage approaches the output. This dual mode

• Integrated high and low-side gate drivers

approach maintains regulation over a wide range of

• Programmable soft-start time input voltages with optimal conversion efficiency in

the buck mode and a glitch-free output during mode

• Ultra low shutdown current

transitions. This easy to use controller includes

• Enable input wide bandwidth error amplifier

drivers for the high side buck MOSFET and the low

• 1.5% feedback reference accuracy

side boost MOSFET. The regulators control method

is based upon current mode control utilizing an

• Thermal shutdown

emulated current ramp. Emulated current mode

control reduces noise sensitivity of the pulse-width

PACKAGE

modulation circuit, allowing reliable control of the very

• HTSSOP-20 (Exposed pad)

small duty cycles necessary in high input voltage

applications. Additional protection features include

current limit, thermal shutdown and an enable input.

The device is available in a power enhanced

HTSSOP-20 package featuring an exposed die attach

pad to aid thermal dissipation.

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 (37 pages)

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LM5118, LM5118-Q1 www.ti.com SNVS566G – APRIL 2008 – REVISED FEBRUARY 2013 Wide Voltage Range Buck-Boost Controller Check for Samples: LM5118, LM5118-Q1 FEATURES DESCRIPTION • The LM5118 wide voltage range Buck-Boost switching regulator controller features all of the functions necessary to implement a high performance, cost efficient Buck-Boost regulator using a minimum of external components.
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LM5118, LM5118-Q1 SNVS566G – APRIL 2008 – REVISED FEBRUARY 2013 www.ti.
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LM5118, LM5118-Q1 www.ti.com SNVS566G – APRIL 2008 – REVISED FEBRUARY 2013 Package HTSSOP-20 (Exposed pad) Connection Diagram 1 20 HS UVLO VIN 2 19 HO RT 3 18 HB EN 4 17 VCCX RAMP 5 16 VCC AGND 6 15 LO SS 7 14 PGND FB 8 13 CSG COMP 9 12 CS VOUT 10 11 SYNC Figure 1.
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LM5118, LM5118-Q1 SNVS566G – APRIL 2008 – REVISED FEBRUARY 2013 www.ti.com PIN DESCRIPTIONS Pin Name Description 1 VIN 2 UVLO Input supply voltage. 3 RT The internal oscillator frequency is set with a single resistor between this pin and the AGND pin. The recommended frequency range is 50 kHz to 500 kHz. 4 EN If the EN pin is below 0.5V, the regulator will be in a low power state drawing less than 10 µA from VIN. EN must be raised above 3V for normal operation. 5 RAMP Ramp control signal.
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LM5118, LM5118-Q1 www.ti.com SNVS566G – APRIL 2008 – REVISED FEBRUARY 2013 Absolute Maximum Ratings (1) VIN, EN, VOUT to GND -0.3V to 76V VCC, LO, VCCX, UVLO to GND (2) -0.3 to 15V HB to HS -0.3 to 15V HO to HS -0.3 to HB+0.3V HS to GND -4V to 76V CSG, CS to GND -0.3V to +0.3V RAMP, SS, COMP, FB, SYNC, RT to GND -0.
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LM5118, LM5118-Q1 SNVS566G – APRIL 2008 – REVISED FEBRUARY 2013 www.ti.com Electrical Characteristics Limits in standard type are for TJ = 25°C only; limits in boldface type apply over the junction temperature range of -40°C to +125°C. Unless otherwise specified, the following conditions apply: VIN = 48V, VCCX = 0V, EN = 5V, RT = 29.11 kΩ, No load on LO and HO (1). Symbol Parameter Conditions IBIAS VIN Operating Current IBIASX ISTDBY Min Typ Max Units VCCX = 0V 4.5 5.
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LM5118, LM5118-Q1 www.ti.com SNVS566G – APRIL 2008 – REVISED FEBRUARY 2013 Electrical Characteristics (continued) Limits in standard type are for TJ = 25°C only; limits in boldface type apply over the junction temperature range of -40°C to +125°C. Unless otherwise specified, the following conditions apply: VIN = 48V, VCCX = 0V, EN = 5V, RT = 29.11 kΩ, No load on LO and HO (1). Symbol Parameter Conditions Min Typ Max Units fSW1 Frequency 1 RT = 29.
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LM5118, LM5118-Q1 SNVS566G – APRIL 2008 – REVISED FEBRUARY 2013 www.ti.com Typical Performance Characteristics Efficiency vs VIN and IOUT VOUT = 12V 100 90 3 AMP x 85 CURRENT LIMIT THRESHOLD (mV) x EFFICIENCY (%) -100 xxx xx 95 x 1 AMP x 2 AMP x 80 75 Current Limit Threshold vs VOUT/VIN VOUT = 12V 0 x 10 20 30 40 50 60 -125 -150 -175 -200 -225 -250 -275 65 70 70 75 VIN (V) 85 Figure 3.
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LM5118, LM5118-Q1 www.ti.com SNVS566G – APRIL 2008 – REVISED FEBRUARY 2013 Typical Performance Characteristics (continued) Oscillator Frequency vs RT 600 500 FOSC (kHz) 400 300 200 100 0 0 20 40 60 80 100 120 140 160 RT (k:) Figure 8.
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LM5118, LM5118-Q1 SNVS566G – APRIL 2008 – REVISED FEBRUARY 2013 www.ti.com BLOCK DIAGRAM AND TYPICAL APPLICATION CIRCUIT 17 LM5118 Vin (4V - 75V ) VIN 1 VCCX 7V VIN VCC 16 REGULATOR VCC UVLO R8 C8 C2 C1 4 EN 3.9V 3V 5 PA THERMAL SHUTDOWN SHUTDOWN AND STANDBY MODE CONTROL R1 HB 18 C13 HB UVLO 2 DISABLE UVLO R2 C12 1.23V Vin HICCUP MODE FAULT TIMER 10 PA 7 SS Q1 CLK 5V PWM C4 S Q R Q HO 19 HS 20 L1 LEVEL SHIFT D2 VOUT 1.
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LM5118, LM5118-Q1 www.ti.com SNVS566G – APRIL 2008 – REVISED FEBRUARY 2013 DETAILED OPERATING DESCRIPTION The LM5118 high voltage switching regulator features all of the functions necessary to implement an efficient high voltage buck or buck-boost regulator using a minimum of external components. The regulator switches smoothly from buck to buck-boost operation as the input voltage approaches the output voltage, allowing operation with the input greater than or less than the output voltage.
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LM5118, LM5118-Q1 SNVS566G – APRIL 2008 – REVISED FEBRUARY 2013 www.ti.com VIN Buck Switch Current HB Q1 HO D2 VOUT HS D1 LM5118 Diode Current CS CSG Q2 LO Figure 11. Buck-Boost Mode Operation 100 90 70 60 50 40 30 DUTY CYCLE (%) 80 20 10 18 17 16 15 14 13 12 0 VIN (V) Figure 12.
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LM5118, LM5118-Q1 www.ti.com SNVS566G – APRIL 2008 – REVISED FEBRUARY 2013 OPERATION MODES Figure 12 illustrates how duty cycle affects the operational mode and is useful for reference in the following discussions. Initially, only the buck switch is active and the buck duty cycle increases to maintain output regulation as VIN decreases. When VIN is approximately equal to 15.5V, the boost switch begins to operate with a low duty cycle.
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LM5118, LM5118-Q1 SNVS566G – APRIL 2008 – REVISED FEBRUARY 2013 www.ti.com FUNCTIONAL DESCRIPTION High Voltage Start-Up Regulator The LM5118 contains a dual mode, high voltage linear regulator that provides the VCC bias supply for the PWM controller and the MOSFET gate driver. The VIN input pin can be connected directly to input voltages as high as 75V. For input voltages below 10V, an internal low dropout switch connects VCC directly to VIN. In this supply range, VCC is approximately equal to VIN.
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LM5118, LM5118-Q1 www.ti.com SNVS566G – APRIL 2008 – REVISED FEBRUARY 2013 If a current limit fault exists for more than 256 clock cycles, the regulator will enter a “hiccup” mode of current limiting and the UVLO pin will be pulled low by an internal switch. This switch turns off when the UVLO pin approaches ground potential allowing the UVLO pin to rise.
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LM5118, LM5118-Q1 SNVS566G – APRIL 2008 – REVISED FEBRUARY 2013 www.ti.com v Buck: ( 5 PA x ( Vin - Vout ) + 50 PA ) x Emulated Ramp Buck - Boost: ( 5 PA x Vin + 50 PA ) x ton Cramp ton Cramp Pedestal Level = 10 x Rs (volts/amp) t Ton Figure 17. Composition of Emulated Current Signal Ramp Generator The ramp signal of a pulse-width modulator with current mode control is typically derived directly from the buck switch drain current.
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LM5118, LM5118-Q1 www.ti.com SNVS566G – APRIL 2008 – REVISED FEBRUARY 2013 RS x A = CRAMP = gm x L CRAMP gm x L A x RS where • • gm is the ramp generator transconductance (5 µA/V) A is the current sense amplifier gain (10V/V) (4) The ramp capacitor should be located very close to the device and connected directly to the RAMP and AGND pins.
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LM5118, LM5118-Q1 SNVS566G – APRIL 2008 – REVISED FEBRUARY 2013 www.ti.com Current Limit In the buck mode the average inductor current is equal to the output current (IOUT). In buck-boost mode the average inductor current is approximately equal to: Iout x 1 + VOUT VIN (6) Consequently, the inductor current in buck-boost mode is much larger especially when VOUT is large relative to VIN. The LM5118 provides a current monitoring scheme to protect the circuit from possible over-current conditions.
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LM5118, LM5118-Q1 www.ti.com SNVS566G – APRIL 2008 – REVISED FEBRUARY 2013 Maximum Duty Cycle Each conduction cycle of the buck switch is followed by a forced minimum off-time of 400ns to allow sufficient time for the recirculating diode current to be sampled. This forced off-time limits the maximum duty cycle of the controller.
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LM5118, LM5118-Q1 SNVS566G – APRIL 2008 – REVISED FEBRUARY 2013 www.ti.com HO Output The LM5118 contains a high side, high current gate driver and associated high voltage level shift. This gate driver circuit works in conjunction with an internal diode and an external bootstrap capacitor. A 0.1 µF ceramic capacitor, connected with short traces between the HB pin and HS pin is recommended for most circuit configurations. The size of the bootstrap capacitor depends on the gate charge of the external FET.
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LM5118, LM5118-Q1 www.ti.com SNVS566G – APRIL 2008 – REVISED FEBRUARY 2013 APPLICATION INFORMATION The procedure for calculating the external components is illustrated with the following design example. The designations used in the design example correlate to the final schematic shown in Figure 26. The design specifications are: • VOUT = 12V • VIN = 5V to 75V • F = 300 kHz • Minimum load current (CCM operation) = 600 mA • Maximum load current = 3A R7 = RT RT sets the oscillator switching frequency.
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LM5118, LM5118-Q1 SNVS566G – APRIL 2008 – REVISED FEBRUARY 2013 L1 = www.ti.com VOUT (VIN1 - VOUT) Buck Mode VIN1 x f x IRIPPLE VIN2 (VOUT) L1 = (VOUT + VIN2) x f x IRIPPLE Buck-Boost Mode where • • • • • • VOUT is the output voltage VIN1 is the maximum input voltage f is the switching frequency IRIPPLE is the selected inductor peak to peak ripple current (1.2 A selected for this example) VIN2 is the minimum input voltage (10) The resulting inductor values are: L1 = 28 µH, Buck Mode L1 = 9.
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LM5118, LM5118-Q1 www.ti.com SNVS566G – APRIL 2008 – REVISED FEBRUARY 2013 R13(BUCK-BOOST) = 2.5V 10 x IPEAK (13) R13(BUCK-BOOST) = 18.7 mΩ A RSENSE value of no more than 18.7 mΩ must be used to ensure the required maximum output current in the buck-boost mode. A value of 15 mΩ was selected for component tolerances and is a standard value.
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LM5118, LM5118-Q1 SNVS566G – APRIL 2008 – REVISED FEBRUARY 2013 www.ti.com D4 A Schottky type recirculating diode is required for all LM5118 applications. The near ideal reverse recovery characteristics and low forward voltage drop are particularly important diode characteristics for high input voltage and low output voltage applications. The reverse recovery characteristic determines how long the current surge lasts each cycle when the buck switch is turned on.
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LM5118, LM5118-Q1 www.ti.com SNVS566G – APRIL 2008 – REVISED FEBRUARY 2013 C16 = CSS The capacitor at the SS pin determines the soft-start time, i.e. the time for the reference voltage and the output voltage, to reach the final regulated value. The time is determined from: tSS = C16 x 1.23V 10 PA (22) and assumes a current limit>Iload + ICout For this application, a C16 value of 0.1 µF was chosen which corresponds to a soft-start time of about 12 ms.
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LM5118, LM5118-Q1 SNVS566G – APRIL 2008 – REVISED FEBRUARY 2013 www.ti.com SNUBBER A snubber network across the buck recirculating diode reduces ringing and spikes at the switching node. Excessive ringing and spikes can cause erratic operation and increase noise at the regulator output. In the limit, spikes beyond the maximum voltage rating of the LM5118 or the recirculating diode can damage these devices. Selecting the values for the snubber is best accomplished through empirical methods.
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LM5118, LM5118-Q1 www.ti.com SNVS566G – APRIL 2008 – REVISED FEBRUARY 2013 ERROR AMPLIFIER CONFIGURATION R4, C18, C17 These components configure the error amplifier gain characteristics to accomplish a stable overall loop gain. One advantage of current mode control is the ability to close the loop with only three feedback components, R4, C18 and C17. The overall loop gain is the product of the modulator gain and the error amplifier gain.
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LM5118, LM5118-Q1 SNVS566G – APRIL 2008 – REVISED FEBRUARY 2013 www.ti.com For the design example, a target loop bandwidth (crossover frequency) of 2.0 kHz was selected (about 30% of the right-half-plane zero frequency). The error amplifier zero (fz) should be selected at a frequency near that of the modulator pole and much less than the target crossover frequency. This constrains the product of R4 and C18 for a desired compensation network zero to be less than 2 kHz.
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LM5118, LM5118-Q1 www.ti.com SNVS566G – APRIL 2008 – REVISED FEBRUARY 2013 a separate bias supply. In the first case, the internal VCC regulator is used to initially bias the VCC pin. After the output voltage is established, the VCC pin bias current is supplied through the VCCX pin, which effectively disables the internal VCC regulator. Any voltage greater than 4.0V can supply VCC bias through the VCCX pin. However, the voltage applied to the VCCX pin should never exceed 15V.
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LM5118, LM5118-Q1 SNVS566G – APRIL 2008 – REVISED FEBRUARY 2013 www.ti.com The highest power dissipating components are the two power MOSFETs, the recirculating diode, and the output diode. The easiest way to determine the power dissipated in the MOSFETs is to measure the total conversion losses (PIN - POUT), then subtract the power losses in the Schottky diodes, output inductor and any snubber resistors. An approximation for the recirculating Schottky diode loss is: P = (1-D) x IOUT x VFWD.
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LM5118, LM5118-Q1 www.ti.com SNVS566G – APRIL 2008 – REVISED FEBRUARY 2013 REVISION HISTORY Changes from Revision F (February 2013) to Revision G • 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.
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PACKAGE MATERIALS INFORMATION www.ti.com 8-Apr-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) LM5118MHX/NOPB HTSSOP PWP 20 2500 330.0 16.4 LM5118Q1MHX/NOPB HTSSOP PWP 20 2500 330.0 16.4 Pack Materials-Page 1 B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant 6.95 7.1 1.6 8.0 16.0 Q1 6.95 7.1 1.6 8.0 16.
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PACKAGE MATERIALS INFORMATION www.ti.com 8-Apr-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM5118MHX/NOPB HTSSOP PWP 20 2500 367.0 367.0 35.0 LM5118Q1MHX/NOPB HTSSOP PWP 20 2500 367.0 367.0 35.
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MECHANICAL DATA PWP0020A MXA20A (Rev C) www.ti.
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