National Semiconductor LM2716 Technical data

February 2004

LM2716
Dual (Step-up and Step-down) PWM DC/DC Converter

LM2716 Dual (Step-up and Step-down) PWM DC/DC Converter

General Description

The LM2716 is composed of two PWM DC/DC converters. A
buck (step-down) converter is used to generate a fixed out­put voltage. A boost (step-up) converter is used to generate
an adjustable output voltage. Both converters feature low

(0.16Ω and 0.12Ω) internal switches for maximum

R

DSON

efficiency. Operating frequency can be adjusted anywhere
between 300kHz and 600kHz allowing the use of small
external components. External soft-start pins for each en­ables the user to tailor the soft-start times to a specific
application. Each converter may also be shut down indepen­dently with its own shutdown pin. The LM2716 is available in
a low profile 24-lead TSSOP package.

Typical Application Circuit

Features

n Fixed buck converter with a 1.8A, 0.16Ω, internal switch
n Adjustable boost converter with a 3.6A, 0.12Ω, internal

switch

n Adjustable boost output voltage up to 20V
n Operating input voltage range of 4V to 20V
n Input undervoltage protection
n 300kHz to 600kHz pin adjustable operating frequency
n Over temperature protection
n Small 24-Lead TSSOP package
n Patented current limit circuitry

Applications

n TFT-LCD Displays
n Handheld Devices
n Portable Applications
n Cellular Phones/Digital Camers

20071201

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Connection Diagram

LM2716

Top View

24-Lead TSSOP

20071204

Ordering Information

Order Number Package Type NSC Package Drawing Supplied As

LM2716MT-ADJ TSSOP-24 MTC24 61 Units, Rail

LM2716MTX-ADJ TSSOP-24 MTC24 2500 Units, Tape and Reel

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Pin Description

Pin Name Function

1 PGND Power ground. AGND and PGND pins must be connected together directly at the part.

2 FB1 Buck output voltage feedback input.

3V

4V

C1

BG

5 SS2 Boost soft start pin.

6V

C2

7 FB2 Boost output voltage feedback input.

8 AGND Analog ground. AGND and PGND pins must be connected together directly at the part.

9 AGND Analog ground. AGND and PGND pins must be connected together directly at the part.

10 PGND Power ground. AGND and PGND pins must be connected together directly at the part.

11 PGND Power ground. AGND and PGND pins must be connected together directly at the part.

12 PGND Power ground. AGND and PGND pins must be connected together directly at the part.

13 SW2 Boost power switch input. Switch connected between SW2 pins and PGND pins. SW2

14 SW2 Boost power switch input. Switch connected between SW2 pins and PGND pins. SW2

15 SW2 Boost power switch input. Switch connected between SW2 pins and PGND pins. SW2

16 V

17 V

IN

IN

18 SHDN2

19 FSLCT Switching frequency select input. Use a resistor to set the frequency anywhere between

20 SS1 Buck soft start pin.

21 SHDN1

22 CB1 Buck converter bootstrap capacitor connection.

23 V

IN

24 SW1 Buck power switch input. Switch connected between V

Buck compensation network connection. Connected to the output of the voltage error
amplifier.

Bandgap connection.

Boost compensation network connection. Connected to the output of the voltage error
amplifier.

pins should be connected directly together at the device.

pins should be connected directly together at the device.

pins should be connected directly together at the device.

Analog power input. VINpins must be connected together directly at the DUT.

Analog power input. VINpins must be connected together directly at the DUT.

Shutdown pin for Boost converter. Active low.

300kHz and 600kHz.

Shutdown pin for Buck converter. Active low.

Analog power input. VINpins must be connected together directly at the DUT.

pins and SW1 pin.

IN

LM2716

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Block Diagram

LM2716

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20071203

LM2716

Absolute Maximum Ratings (Note 1)

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

V

IN

SW1 Voltage −0.3V to 22V

SW2 Voltage −0.3V to 22V

−0.3V to 22V

Power Dissipation(Note 2) Internally Limited

Lead Temperature 300˚C

Vapor Phase (60 sec.) 215˚C

Infrared (15 sec.) 220˚C

ESD Susceptibility (Note 3)

Human Body Model 2kV

Machine Model 200V

FB1 Voltage −0.3V to 7V

FB2 Voltage −0.3V to 7V

V

Voltage 1.75V ≤ VC1≤ 2.25V

C1

V

Voltage 0.965V ≤ VC2≤ 1.565V

C2

SHDN1 Voltage

SHDN2 Voltage

−0.3V to 7.5V

−0.3V to 7.5V

SS1 Voltage −0.3V to 2.1V

SS2 Voltage −0.3V to 0.6V

FSLCT Voltage AGND to 5V

CB1 Voltage V

+7V(VIN=VSW)

IN

Operating Conditions

Operating Junction
Temperature Range
(Note 4) −40˚C to +125˚C

Storage Temperature −65˚C to +150˚C

Supply Voltage 4V to 20V

SW1 Voltage 20V

SW2 Voltage 20V

Maximum Junction Temperature 150˚C

Electrical Characteristics

Specifications in standard type face are for TJ= 25˚C and those with boldface type apply over the full Operating Tempera­ture Range (T

Symbol Parameter Conditions

I

Q

V

BG

I

(Note 6) Buck Switch Current Limit 95% Duty Cycle (Note 7) 1.8 A

CL1

I

(Note 6) Boost Switch Current Limit 95% Duty Cycle (Note 7) 3.6 A

CL2

I

FB1

I

FB2

V

IN

g

m1

g

m2

A

V1

A

V2

D

MAX

F

SW

I

SHDN1

I

SHDN2

I

L1

I

L2

R

DSON1

R

DSON2

= −40˚C to +125˚C) Unless otherwise specified. VIN= 5V and IL= 0A, unless otherwise specified.

J

Total Quiescent Current (both
switchers)

Min

(Note 4)

Not Switching 2.8 3.5 mA

Switching, switch open 4 4.5 mA

V

=0V 9 15 µA

SHDN

Typ

(Note 5)

Max

(Note 4)

Bandgap Voltage 1.235 1.26 1.285 V

Buck FB Pin Bias Current
(Note 8)

Boost FB Pin Bias Current
(Note 8)

V

V

FB1

FB2

= 3.3V

= 1.265V

65 75 µA

27 55 nA

Input Voltage Range 420V

Buck Error Amp
Transconductance

Boost Error Amp
Transconductance

∆I = 20µA

∆I = 5µA

1200 µmho

175 µmho

Buck Error Amp Voltage Gain 100 V/V

Boost Error Amp Voltage
Gain

135 V/V

Maximum Duty Cycle 90 95 98 %

Switching Frequency RF= 47.5kΩ 250 300 350 kHz

R

= 22.6kΩ 500 600 700 kHz

F

Buck Shutdown Pin Current 0V<V

Boost Shutdown Pin Current 0V<V

SHDN1

SHDN2

<

7.5V −5 5 µA

<

7.5V −5 5 µA

Buck Switch Leakage Current VDS= 20V 0.2 5 µA

Boost Switch Leakage
Current

Buck Switch R

Boost Switch R

DSON

DSON

VDS= 20V

0.2 3 µA

160 mΩ

120 mΩ

Units

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Electrical Characteristics (Continued)

Specifications in standard type face are for TJ= 25˚C and those with boldface type apply over the full Operating Tempera-

LM2716

ture Range (T

Symbol Parameter Conditions

Th

SHDN1

Th

SHDN2

I

SS1

I

SS2

UVP On Threshold 3.35 3.8 4.0

θ

JA

Note 1: Absolute maximum ratings are limits beyond which damage to the device may occur. Operating Ratings are conditions for which the device is intended to
be functional, but device parameter specifications may not be guaranteed. For guaranteed specifications and test conditions, see the Electrical Characteristics.

Note 2: The maximum allowable power dissipation is a function of the maximum junction temperature, T
and the ambient temperature, T
temperature is calculated using: P
regulator will go into thermal shutdown.

Note 3: The human body model is a 100 pF capacitor discharged through a 1.5kΩ resistor into each pin. The machine model is a 200pF capacitor discharged
directly into each pin.

Note 4: All limits guaranteed at room temperature (standard typeface) and at temperature extremes (bold typeface). All room temperature limits are 100% tested
or guaranteed through statistical analysis. All limits at temperature extremes are guaranteed via correlation using standard Statistical Quality Control (SQC) methods.
All limits are used to calculate Average Outgoing Quality Level (AOQL).

Note 5: Typical numbers are at 25˚C and represent the most likely norm.

Note 6: Duty cycle affects current limit due to ramp generator.

Note 7: Current limit at 95% duty cycle. See TYPICAL PERFORMANCE section for Switch Current Limit vs. V

Note 8: Bias current flows into FB pin.

Note 9: Refer to National’s packaging website for more detailed thermal information and mounting techniques for the TSSOP package.

= −40˚C to +125˚C) Unless otherwise specified. VIN= 5V and IL= 0A, unless otherwise specified.

J

Min

(Note 4)

Typ

(Note 5)

Max

(Note 4)

Buck SHDN Threshold Output High 1.37 2

Output Low 0.8 1.35

Boost SHDN Threshold Output High 1.37 2

Output Low 0.8 1.35

Buck Soft Start Pin Current 6 9.5 12 µA

Boost Soft Start Pin Current 15 19 22 µA

Off Threshold 3.10 3.6 3.9

Thermal Resistance

TSSOP, package only 115

(Note 9)

(MAX), the junction-to-ambient thermal resistance, θJA,

. See the Electrical Characteristics table for the thermal resistance. The maximum allowable power dissipation at any ambient

A

(MAX) = (T

D

J(MAX)−TA

)/θJA. Exceeding the maximum allowable power dissipation will cause excessive die temperature, and the

J

IN

Units

V

V

V

˚C/W

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