NSC LM5116 Datasheet

April 2007

LM5116
Wide Range Synchronous Buck Controller

General Description

The LM5116 is a synchronous buck controller intended for
step-down regulator applications from a high voltage or widely
varying input supply. The control method is based upon cur­rent mode control utilizing an emulated current ramp. Current
mode control provides inherent line feed-forward, cycle by
cycle current limiting and ease of loop compensation. The use
of an emulated control ramp reduces noise sensitivity of the
pulse-width modulation circuit, allowing reliable control of
very small duty cycles necessary in high input voltage appli­cations. The operating frequency is programmable from
50kHz to 1MHz. The LM5116 drives external high-side and
low-side NMOS power switches with adaptive dead-time con­trol. A user-selectable diode emulation mode enables discon­tinuous mode operation for improved efficiency at light load
conditions. A low quiescent current shutdown disables the
controller and consumes less than 10µA of total input current.
Additional features include a high voltage bias regulator, au­tomatic switch-over to external bias for improved efficiency,
thermal shutdown, frequency synchronization, cycle by cycle
current limit and adjustable line under-voltage lockout. The
device is available in a power enhanced TSSOP-20 package
featuring an exposed die attach pad to aid thermal dissipation.

Features

■

Emulated peak current mode

■

Wide operating range up to 100V

■

Low IQ shutdown (<10µA)

■

Drives standard or logic level MOSFETs

■

Robust 3.5A peak gate drive

■

Free-run or synchronous operation to 1MHz

■

Optional diode emulation mode

■

Programmable output from 1.215V to 80V

■

Precision 1.5% voltage reference

■

Programmable current limit

■

Programmable soft-start

■

Programmable line under-voltage lockout

■

Automatic switch to external bias supply

■

TSSOP-20EP exposed pad

■

Thermal shutdown

Typical Application

30007501

© 2007 National Semiconductor Corporation 300075 www.national.com

LM5116 Wide Range Synchronous Buck Controller

Connection Diagram

30007502

Top View

See NS Package Numbers MXA20A

Ordering Information

Ordering Number Package Type NSC Package Drawing Supplied As

LM5116MH TSSOP-20EP MXA20A 73 Units Per Anti-Static Tube

LM5116MHX TSSOP-20EP MXA20A 2500 units shipped as Tape & Reel

Pin Descriptions

Pin Name Description

1 VIN Chip supply voltage, input voltage monitor and input to the VCC regulator.

2 UVLO If the UVLO pin is below 1.215V, the regulator will be in standby mode (VCC regulator running, switching regulator

disabled). If the UVLO pin voltage is above 1.215V, the regulator is operational. An external voltage divider can be
used to set an under-voltage shutdown threshold. There is a fixed 5µA pull up current on this pin when EN is high.
UVLO is pulled to ground in the event a current limit condition exists for 256 clock cycles.

3 RT/

SYNC

The internal oscillator is set with a single resistor between this pin and the AGND pin. The recommended frequency
range is 50kHz to 1MHz. The internal oscillator can be synchronized to an external clock by AC coupling a positive
edge onto this node.

4 EN If the EN pin is below 0.5V, the regulator will be in a low power state drawing less than 10µA from VIN. EN must be

pulled above 3.3V 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 current mode control.

6 AGND Analog ground.

7 SS An external capacitor and an internal 10µA current source set the soft start time constant for the rise of the error amp

reference. The SS pin is held low during VCC < 4.5V, UVLO < 1.215V, EN input low or thermal shutdown.

8 FB Feedback signal from the regulated output. This pin is connected to the inverting input of the internal error amplifier.

The regulation threshold is 1.215V.

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

FB pin.

10 VOUT Output monitor. Connect directly to the output voltage.

11 DEMB Low-side MOSFET source voltage monitor for diode emulation. For start-up into a pre-biased load, tie this pin to

ground at the CSG connection. For fully synchronous operation, use an external series resistor between DEMB and
ground to raise the diode emulation threshold above the low-side SW on-voltage.

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LM5116

Pin Name Description

12 CS Current sense amplifier input. Connect to the top of the current sense resistor or the drain of the low-sided MOSFET

if R

DS(ON)

current sensing is used.

13 CSG Current sense amplifier input. Connect to the bottom of the sense resistor or the source of the low-side MOSFET if

R

DS(ON)

current sensing is used.

14 PGND Power ground.

15 LO Connect to the gate of the low-side synchronous MOSFET through a short, low inductance path.

16 VCC 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 VCC. If VCCX > 4.5V, VCCX is internally connected to VCC and the internal

VCC regulator is disabled. If VCCX is unused, it should be connected to ground.

18 HB High-side driver supply for bootstrap gate drive. Connect to the cathode of the bootstrap diode and the positive

terminal of the bootstrap capacitor. The bootstrap capacitor supplies current to charge the high-side MOSFET gate
and should be placed as close to the controller as possible.

19 HO Connect to the gate of the high-side synchronous MOSFET through a short, low inductance path

20 SW Switch node. Connect to the negative terminal of the bootstrap capacitor and the source terminal of the high-side

MOSFET.

EP EP Exposed pad. Solder to ground plane.

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LM5116

Absolute Maximum Ratings (Note 1)

If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.

VIN to GND -0.3V to 100V
VCC, VCCX, UVLO to GND (Note 3) -0.3 to 16V
SW, CS to GND -3.0 to 100V
HB to SW -0.3 to 16V
HO to SW -0.3 to HB+0.3V
VOUT to GND -0.3 to 100V
CSG to GND -1V to 1V
LO to GND -0.3 to VCC+0.3V
SS to GND -0.3 to 7V
FB to GND -0.3 to 7V
DEMB to GND -0.3 to VCC

RT to GND -0.3 to 7V
EN to GND -0.3 to 100V
ESD Rating

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

Operating Ratings (Note 1)

VIN 6V to 100V
VCC, VCCX 4.75V to 15V
HB to SW 4.75V to 15V
DEMB to GND -0.3V to 2V
Junction Temperature -40°C to +125°C

Note: RAMP, COMP are output pins. As such they are not specified to have
an external voltage applied.

Electrical Characteristics Limits in standard type are for T

J

= 25°C only; limits in boldface type apply over the
junction temperature range of -40°C to +125°C and are provided for reference only. Unless otherwise specified, the following
conditions apply: VIN = 48V, VCC = 7.4V, VCCX = 0V, EN = 5V, RT = 16kΩ, no load on LO and HO.

Symbol Parameter Conditions Min Typ Max Units

VIN Supply

I

BIAS

VIN Operating Current VCCX = 0V, VIN = 48V 5 7 mA

VCCX = 0V, VIN = 100V 5.9 8 mA

I

BIASX

VIN Operating Current VCCX = 5V, VIN = 48V 1.2 1.7 mA

VCCX = 5V, VIN = 100V 1.6 2.3 mA

I

STDBY

VIN Shutdown Current EN = 0V, VIN = 48V 1 10 µA

EN = 0V, VIN = 100V 1 µA

VCC Regulator

V

CC(REG)

VCC Regulation 7.1 7.4 7.7 V

VCC LDO Mode Turn-off 10.6 V

VCC Regulation VIN = 6V 5.0 5.9 6.0 V

VCC Sourcing Current Limit VCC = 0V 15 26 mA

VCCX Switch Threshold VCCX Rising 4.3 4.5 4.7 V

VCCX Switch Hysteresis 0.25 V

VCCX Switch R

DS(ON)

ICCX = 10mA 3.8 6.2

Ω

VCCX Leakage VCCX = 0V -200 nA

VCCX Pull- down Resistance VCCX = 3V 100

kΩ

VCC Under-voltage Threshold VCC Rising 4.3 4.5 4.7 V

VCC Under-voltage Hysteresis 0.2 V

HB DC Bias Current HB-SW = 15V 125 200 µA

EN Input

VIL max EN Input Low Threshold 0.5 V

VIH min EN Input High Threshold 3.3 V

EN Input Bias Current VEN = 3V -7.5 -3 1 µA

EN Input Bias Current VEN = 0.5V -1 0 1 µA

EN Input Bias Current VEN = 100V 20 90 µA

UVLO Thresholds

UVLO Standby Threshold UVLO Rising 1.170 1.215 1.262 V

UVLO Threshold Hysteresis 0.1 V

UVLO Pull-up Current Source UVLO = 0V 5.4 µA

UVLO Pull-down R

DS(ON)

80 210

Ω

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LM5116

Symbol Parameter Conditions Min Typ Max Units

Soft Start

SS Current Source SS = 0V 8 11 14 µA

SS Diode Emulation Ramp Disable

Threshold

SS Rising 3 V

SS to FB Offset FB = 1.25V 160 mV

SS Output Low Voltage Sinking 100µA, UVLO = 0V 45 mV

Error Amplifier

V

REF

FB Reference Voltage Measured at FB pin, FB =

COMP

1.195 1.215 1.231 V

FB Input Bias Current FB = 2V 15 500 nA

COMP Sink/Source Current 3 mA

A

OL

DC Gain 80 dB

f

BW

Unity Gain Bandwidth 3 MHz

PWM Comparators

t

HO(OFF)

Forced HO Off-time 320 450 580 ns

t

ON(min)

Minimum HO On-time VIN = 80V, C

RAMP

= 50pF 100 ns

Oscillator

f

SW1

Frequency 1

RT = 16kΩ

180 200 220 kHz

f

SW2

Frequency 2

RT = 5kΩ

480 535 590 kHz

RT output voltage 1.191 1.215 1.239 V

RT sync positive threshold 3.0 3.5 4.0 V

Current Limit

V

CS(TH)

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

VCCX = 0V, RAMP = 0V 94 110 126 mV

V

CS(THX)

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

VCCX = 5V, RAMP = 0V 105 122 139 mV

CS Bias Current CS = 100V -1 1 µA

CS Bias Current CS = 0V 90 125 µA

CSG Bias Current CSG = 0V 90 125 µA

Current Limit Fault Timer

RT = 16kΩ, (200kHz), (256
clock cycles)

1.28 ms

RAMP Generator

I

R1

RAMP Current 1 VIN = 60V, VOUT=10V 235 285 335 µA

I

R2

RAMP Current 2 VIN = 10V, VOUT = 10V 21 28 35 µA

VOUT Bias Current VOUT = 36V 200 µA

RAMP Output Low Voltage VIN = 60V, VOUT = 10V 265 mV

Diode Emulation

SW Zero Cross Threshold -6 mV

DEMB Output Current DEMB = 0V, SS = 1.25V 1.6 2.7 3.8 µA

DEMB Output Current DEMB =0V, SS = 2.8V 28 38 48 µA

DEMB Output Current DEMB = 0V, SS = Regulated

by FB

45 65 85 µA

LO Gate Driver

V

OLL

LO Low-state Output Voltage ILO = 100mA 0.08 0.17 V

V

OHL

LO High-state Output Voltage ILO = -100mA, V

OHL

= VCC -

V

LO

0.25 V

LO Rise Time C-load = 1000pF 18 ns

LO Fall Time C-load = 1000pF 12 ns

I

OHL

Peak LO Source Current VLO = 0V 1.8 A

I

OLL

Peak LO Sink Current VLO = VCC 3.5 A

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LM5116

Symbol Parameter Conditions Min Typ Max Units

HO Gate Driver

V

OLH

HO Low-state Output Voltage IHO = 100mA 0.17 0.27 V

V

OHH

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

OHH

= VHB –

V

HO

0.45 V

HO Rise Time C-load = 1000pF 19 ns

HO High-side Fall Time C-load = 1000pF 13 ns

I

OHH

Peak HO Source Current VHO = 0V 1 A

I

OLH

Peak HO Sink Current VHO = VCC 2.2 A

HB to SW under-voltage 3 V

Switching Characteristics

LO Fall to HO Rise Delay C-load = 0 75 ns

HO Fall to LO Rise Delay C-load = 0 70 ns

Thermal

T

SD

Thermal Shutdown Rising 170 °C

Thermal Shutdown Hysteresis 15 °C

θ

JA

Junction to Ambient 40 °C/W

θ

JC

Junction to Case 4 °C/W

Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the component may occur. Operating Ratings are conditions under which operation
of the device is guaranteed. Operating Ratings do not imply guaranteed performance limits. For guaranteed performance limits and associated test conditions,
see the Electrical Characteristics tables.

Note 2: The human body model is a 100pF capacitor discharged through a 1.5kΩ resistor into each pin. LO, HO and HB are rated at 1kV. 2kV rating for all pins
except VIN which is rated for 1.5kV.

Note 3: These pins must not exceed VIN.

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LM5116

Typical Performance Characteristics

Typical Application Circuit Efficiency

30007503

Driver Source Current vs VCC

30007504

Driver Dead-time vs Temperature

30007505

HO High R

DS(ON)

vs VCC

30007506

Driver Sink Current vs VCC

30007507

HO Low R

DS(ON)

vs VCC

30007508

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LM5116

LO High R

DS(ON)

vs VCC

30007509

EN Input Threshold vs Temperature

30007510

LO Low R

DS(ON)

vs VCC

30007511

HB to SW UVLO vs Temperature

30007512

Forced HO Off-time vs Temperature

VCCX = 5V

30007513

HB DC Bias Current vs Temperature

30007514

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LM5116