National Semiconductor LM5118 Technical data

LM5118
Wide Voltage Range Buck-Boost Controller

LM5118 Wide Voltage Range Buck-Boost Controller

May 19, 2008

General 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. The
Buck-Boost topology maintains output voltage regulation
when the input voltage is either less than or greater than the
output voltage making it especially suitable for automotive
applications. The LM5118 operates as a buck regulator while
the input voltage is sufficiently greater than the regulated out­put voltage and gradually transitions to the buck-boost mode
as the input voltage approaches the output. This dual mode
approach maintains regulation over a wide range of input
voltages with optimal conversion efficiency in the buck mode
and a glitch-free output during mode transitions. This easy to
use controller includes drivers for the high side buck MOSFET
and the low side boost MOSFET. The regulator’s control
method is based upon current mode control utilizing an em­ulated current ramp. Emulated current mode control reduces
noise sensitivity of the pulse-width modulation circuit, allow­ing reliable control of the very 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 TSSOP-20
package featuring an exposed die attach pad to aid thermal
dissipation.

Typical Application Circuit

Features

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

■

Emulated peak current mode control

■

Smooth transition between step-down and step- up modes

■

Switching frequency programmable to 500KHz

■

Oscillator synchronization capability

■

Internal high voltage bias regulator

■

Integrated high and low-side gate drivers

■

Programmable soft-start time

■

Ultra low shutdown current

■

Enable input wide bandwidth error amplifier

■

1.5% feedback reference accuracy

■

Thermal shutdown

■

Package

TSSOP-20EP (Exposed pad)

30058501

© 2008 National Semiconductor Corporation 300585 www.national.com

Connection Diagram

LM5118

See NS Package Numbers MXA20A

Top View

30058502

Ordering Information

Ordering Number Package Type NSC Package Drawing Supplied As

LM5118MH TSSOP-20EP MXA20A 73 Units Per Anti-Static Tube

LM5118MHX TSSOP-20EP MXA20A 2500 units shipped as Tape & Reel

Pin Descriptions

Pin Name Description

1 VIN Input supply voltage.

2 UVLO If the UVLO pin is below 1.23V, the regulator will be in standby mode (VCC regulator running, switching

regulator disabled). When the UVLO pin exceeds 1.23V, the regulator enters the normal operating mode. An
external voltage divider can be used to set an under-voltage shutdown threshold. A fixed 5 µA current is sourced
out of the EN pin. If a current limit condition exists for 256 consecutive switching cycles, an internal switch pulls
the UVLO pin to ground and then releases.

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. An external capacitor connected between this pin and the AGND pin sets the ramp slope

used for emulated current mode control.

6 AGND Analog ground.

7 SS Soft-Start. An external capacitor and an internal 10 µA current source set the rise time of the error amp

reference. The SS pin is held low when VCC is less than the VCC under-voltage threshold (< 3.7V), when the
UVLO pin is low (< 1.23V), when EN is low (< 0.5V) or when thermal shutdown is active.

8 FB Feedback signal from the regulated output. Connect to the inverting input of the internal error amplifier.

9 COMP Output of the internal error amplifier. The loop compensation network should be connected between COMP

and the FB pin.

10 VOUT Output voltage monitor for emulated current mode control. Connect this pin directly to the regulated output.

11 SYNC Sync input for switching regulator synchronization to an external clock.

12 CS Current sense input. Connect to the diode side of the current sense resistor.

13 CSG Current sense ground input. Connect to the ground side of the current sense resistor.

14 PGND Power Ground.

15 LO Boost MOSFET gate drive output. Connect to the gate of the external boost MOSFET.

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Pin Name Description

16 VCC Output of the bias regulator. Locally decouple to PGND using a low ESR/ESL capacitor located as close to

the controller as possible.

17 VCCX Optional input for an externally supplied bias supply. If the voltage at the VCCX pin is greater than 3.9V, the

internal VCC regulator is disabled and the VCC pin is internally connected to VCCX pin supply. If VCCX is not
used, connect to AGND.

18 HB High side gate driver supply used in bootstrap operation. The bootstrap capacitor supplies current to charge

the high side MOSFET gate. This capacitor should be placed as close to the controller as possible and
connected between HB and HS.

19 HO Buck MOSFET gate drive output. Connect to the gate of the high side buck MOSFET through a short, low

inductance path.

20 HS Buck MOSFET source pin. Connect to the source terminal of the high side buck MOSFET and the bootstrap

capacitor.

EP Solder to the ground plane under the IC to aid in heat dissipation.

LM5118

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Absolute Maximum Ratings (Note 1)

If Military/Aerospace specified devices are required,

LM5118

please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.

VIN, EN, VOUT to GND -0.3V to 76V
VCC, LO, VCCX, UVLO to GND (Note 5) -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 -0.3 to 7V
ESD Rating

HBM (Note 2) 2 kV
Storage Temperature Range -55°C to +150°C
Junction Temperature +150°C

Operating Ratings (Note 1)

VIN (Note 4) 3V to 75V
VCC, VCCX 4.75V to 14V
Junction Temperature -40°C to +125°C

Electrical Characteristics Limits in standard type are for T

= 25°C only; limits in boldface type apply over the

J

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 (Note 3).

Symbol Parameter Conditions Min Typ Max Units

VIN SUPPLY

I

BIAS

I

BIASX

I

STDBY

VIN Operating Current VCCX = 0V 4.5 5.5 mA

VIN Operating Current VCCX = 5V 1 1.85 mA

VIN Shutdown Current EN = 0V 1 10 µA

VCC REGULATOR

V

CC(REG)

V

CC(REG)

VCC Regulation VCCX = 0V 6.8 7 7.2 V

VCC Regulation VCCX = 0V, VIN = 6V 5 5.25 5.5 V

VCC Sourcing Current Limit VCC = 0 21 35 mA

VCCX Switch threshold VCCX Rising 3.68 3.85 4.02 V

VCCX Switch hysterisis 0.2 V

VCCX Switch RDS(ON) ICCX = 10 mA 5 12

VCCX Switch Leakage VCCX = 0V 0.5 1 µA

VCCCX Pull-down Resistance VCCX = 3V 70

VCC Under-Voltage Lockout

VCC Rising 3.52 3.7 3.86 V

Voltage

VCC Under-Voltage Hysterisis 0.21 V

HB DC Bias current HB-HS = 15V 205 260 µA

VC LDO Mode Turn-off 10 V

EN INPUT

V

V

IL max

IH min

EN Input Low Threshold 0.5 V

EN Input High Threshold 3.00 V

EN Input Bias Current VEN = 3V -1 1 µA

EN Input Bias Current VEN = 0.5V -1 1 µA

EN Input Bias Current VEN = 75V 50 µA

UVLO THRESHOLDS

UVLO Standby Threshold UVLO Rising 1.191 1.231 1.271 V

UVLO Threshold Hysteresis 0.105 V

UVLO Pull-up Current Source UVLO = 0V 5 µA

UVLO Pull-down R

DS(ON)

100 200

SOFT- START

SS Current Source SS = 0V 7.5 10.5 13.5 µA

SS to FB Offset FB = 1.23V 150 mV

SS Output Low Voltage Sinking 100 µA, UVLO = 0V 7 mV

ERROR AMPLIFIER

V

REF

FB Reference Voltage Measured at FB pin,

1.212 1.230 1.248 V

FB = COMP

FB Input Bias Current FB = 2V 20 200 nA

Ω

kΩ

Ω

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Symbol Parameter Conditions Min Typ Max Units

COMP Sink/Source Current 3 mA

A

OL

f

BW

DC Gain 80 dB

Unity Bain Bandwidth 3 MHz

PWM COMPARATORS

t

HO(OFF)

T

ON(MIN)

Forced HO Off-time 305 400 495 ns

Minimum HO On-time 70 ns

COMP to Comparator Offset 200 mV

OSCILLATOR (RT PIN)

f

SW1

f

SW2

Frequency 1

Frequency 2

SYNC

Sync threshold falling 1.3 V

CURRENT LIMIT

V

CS(TH)

Cycle-by-cycle Sense Voltage
Threshold (CS-CSG)

V

CS(THX)

Cycle-by-cycle Sense Voltage
Threshold (CS-CSG)

CS Bias Current CS = 0V 45 60 µA

CSG Bias Current CSG = 0V 45 60 µA

Current Limit Fault Timer 256 cycles

RAMP GENERATOR

I

R1

I

R2

I

R3

RAMP Current 1 VIN = 60V, VOUT = 10V 245 305 365 µA

RAMP Current 2 VIN = 12V, VOUT = 12V 95 115 135 µA

RAMP Current 3 VIN = 5V, VOUT = 12V 65 80 95 µA

VOUT Bias Current VOUT = 48V 245 µA

LOW SIDE (LO) GATE DRIVER

V

OLL

V

OHL

LO Low-state Output Voltage ILO = 100 mA 0.095 0.14 0.23 V

LO High-state Output Voltage ILO = -100 mA

LO Rise Time C-load = 1 nF, VCC = 8V 16 ns

LO Fall Time C-load = 1 nF, VCC = 8V 14 ns

I

I

OHL

OLL

Peak LO Source Current VLO = 0V, VCC = 8V 2.2 A

Peak LO Sink Current VLO = VCC = 8V 2.7 A

HIGH SIDE (HO) GATE DRIVER

V

OLH

V

OHH

HO Low-state Output Voltage IHO = 100 mA 0.1 0.135 0.21 V

HO High-state Output Voltage IHO = -100 mA,

HO Rise Time C-load = 1 nF, VCC = 8V 14 ns

HO Fall Time C-load = 1 nF, VCC = 8V 12 ns

I

OHH

I

OLH

Peak HO Source Current VHO = 0V, VCC = 8V 2.2 V

Peak HO Sink Current VHO = VCC = 8V 3.5 V

HB-HS Under Voltage Lock-out 3 V

BUCK-BOOST CHARACTERISTICS

Buck-Boost Mode Buck Duty Cycle (Note 5) 69 75 80 %

THERMAL

T

SD

Thermal Shutdown Temp. 165 °C

Thermal Shutdown Hysterisis 25 °C

θ

JA

θ

JC

Junction to Ambient 40 °C/W

Junction to Case 4 °C/W

RT = 29.11 kΩ

RT = 9.525 kΩ

178 200 224 kHz

450 515 575 kHz

RAMP = 0 Buck Mode -103 -125 -147 mV

RAMP = 0 Buck-Boost Mode -218 -255 -300 mV

0.25 V

V

= VCC-V

OHL

LO

0.25 V

V

= VHB-V

OHH

OH

LM5118

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Note 1: Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is
intended to be functional, but does not guarantee specific performance limits. For guaranteed specifications and test conditions see the Electrical Characteristics.

Note 2: The human body model is a 100pF capacitor discharged through a 1.5 kΩ resistor into each pin.

LM5118

Note 3: Min and Max limits are 100% production tested at 25°C. Limits over the operating temperature range are guaranteed through correlation using Statistical

Quality Control (SQC) methods. Limits are used to calculate National’s Average Outgoing Quality Level (AOQL).

Note 4: 5V VIN is required to initially start the controller.

Note 5: : When the duty cycle exceeds 75%, the LM5118 controller gradually phases into the Buck-Boost mode.

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Typical Performance Characteristics

LM5118

Efficiency vs VIN and IOUT

VOUT = 12V

VCC vs VIN

30058503

Current Limit Threshold vs VOUT/VIN

VOUT = 12V

30058504

VCC vs IVCC

Error Amplifier Gain/Phase

30058505

30058507

30058506

LO and HO Peak Gate Current vs Output Voltage

VCC = 8V

30058508

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LM5118

Oscillator Frequency vs RT

30058509

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