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LM2717

www.ti.com

SNVS253D –MAY 2005–REVISED MARCH 2013

LM2717 Dual Step-Down DC/DC Converter

Check for Samples: LM2717

FEATURES

DESCRIPTION

The LM2717 is composed of two PWM DC/DC buck

• Fixed 3.3V Output Buck Converter with a 2.2A,

(step-down) converters. The first converter is used to

0.16Ω, Internal Switch

generate a fixed output voltage of 3.3V. The second

• Adjustable Buck Converter with a 3.2A, 0.16Ω,

converter is used to generate an adjustable output

Internal Switch

voltage. Both converters feature low R

DSON

(0.16Ω)

internal switches for maximum efficiency. Operating

• Operating Input Voltage Range of 4V to 20V

frequency can be adjusted anywhere between

• Input Undervoltage Protection

300kHz and 600kHz allowing the use of small

• 300kHz to 600kHz Pin Adjustable Operating

external components. External soft-start pins for each

Frequency

enables the user to tailor the soft-start times to a

specific application. Each converter may also be shut

• Over Temperature Protection

down independently with its own shutdown pin. The

• Small 24-Lead TSSOP Package

LM2717 is available in a low profile 24-lead TSSOP

package ensuring a low profile overall solution.

APPLICATIONS

• TFT-LCD Displays

• Handheld Devices

• Portable Applications

• Laptop Computers

Typical Application Circuit

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 (17 pages)

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LM2717 www.ti.com SNVS253D – MAY 2005 – REVISED MARCH 2013 LM2717 Dual Step-Down DC/DC Converter Check for Samples: LM2717 FEATURES DESCRIPTION • The LM2717 is composed of two PWM DC/DC buck (step-down) converters. The first converter is used to generate a fixed output voltage of 3.3V. The second converter is used to generate an adjustable output voltage. Both converters feature low RDSON (0.16Ω) internal switches for maximum efficiency.
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LM2717 SNVS253D – MAY 2005 – REVISED MARCH 2013 www.ti.com Connection Diagram Top View Figure 1. 24-Lead TSSOP See Package Number PW0024A PIN DESCRIPTIONS 2 Pin Name 1 PGND Power ground. PGND and AGND pins must be connected together directly at the part. Function 2 PGND Power ground. PGND and AGND pins must be connected together directly at the part. 3 AGND Analog ground. PGND and AGND pins must be connected together directly at the part. 4 FB1 Fixed buck output voltage feedback input.
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LM2717 www.ti.com SNVS253D – MAY 2005 – REVISED MARCH 2013 Block Diagram FSLCT CB1 VIN + 95% Duty Cycle Limit + OSC SS1 Buck Load Current Measurement FB1 36.5k 20.
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LM2717 SNVS253D – MAY 2005 – REVISED MARCH 2013 www.ti.com Absolute Maximum Ratings (1) (2) VIN −0.3V to 22V SW1 Voltage −0.3V to 22V SW2 Voltage −0.3V to 22V FB1, FB2 Voltages −0.3V to 7V CB1, CB2 Voltages −0.3V to VIN+7V (VIN=VSW) VC1 Voltage 1.75V ≤ VC1 ≤ 2.25V VC2 Voltage 0.965V ≤ VC2 ≤ 1.565V SHDN1 Voltage −0.3V to 7.5V SHDN2 Voltage −0.3V to 7.5V SS1 Voltage −0.3V to 2.1V SS2 Voltage −0.3V to 2.
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LM2717 www.ti.com SNVS253D – MAY 2005 – REVISED MARCH 2013 Electrical Characteristics (continued) Specifications in standard type face are for TJ = 25°C and those with boldface type apply over the full Operating Temperature Range (TJ = −40°C to +125°C). VIN = 5V, IL = 0A, and FSW = 300kHz unless otherwise specified. Symbol ICL1 (3) Parameter Conditions Fixed Buck Switch Current Limit VIN = 8V ICL2 (3) Adjustable Buck Switch Current Limit IB1 Min (1) Typ (2) Max (1) Units (4) 2.
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LM2717 SNVS253D – MAY 2005 – REVISED MARCH 2013 www.ti.com Typical Performance Characteristics Switching IQ vs. Input Voltage (FSW = 300kHz) 16 9 14 8 12 7 QUIESCENT CURRENT (mA) QUIESCENT CURRENT (PA) Shutdown IQ vs. Input Voltage 10 8 6 4 2 6 5 4 3 2 1 0 4 6 8 10 12 14 16 18 20 0 4 INPUT VOLTAGE (V) 6 8 10 12 14 16 18 20 18 20 INPUT VOLTAGE (V) Figure 2. Figure 3. Switching Frequency vs. Input Voltage (FSW = 300kHz) Fixed Buck RDS(ON) vs.
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LM2717 www.ti.com SNVS253D – MAY 2005 – REVISED MARCH 2013 Typical Performance Characteristics (continued) Adjustable Buck Efficiency vs. Load Current (VOUT = 5V) 100 100 90 90 80 80 70 70 EFFICIENCY (%) EFFICIENCY (%) Adjustable Buck Efficiency vs. Load Current (VOUT = 15V) 60 50 40 30 50 40 30 20 20 V IN = 18V 10 V IN = 18V 10 0 0 0 0.5 1 1.5 2 2.5 0 0.5 1 1.5 2 2.5 LOAD CURRENT (A) LOAD CURRENT (A) Figure 8. Figure 9. Fixed Buck Switch Current Limt vs.
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LM2717 SNVS253D – MAY 2005 – REVISED MARCH 2013 www.ti.com BUCK OPERATION PROTECTION (BOTH REGULATORS) The LM2717 has dedicated protection circuitry running during normal operation to protect the IC. The Thermal Shutdown circuitry turns off the power devices when the die temperature reaches excessive levels. The UVP comparator protects the power devices during supply power startup and shutdown to prevent operation at voltages less than the minimum input voltage.
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LM2717 www.ti.com SNVS253D – MAY 2005 – REVISED MARCH 2013 INDUCTOR SELECTION The most critical parameters for the inductor are the inductance, peak current and the DC resistance. The inductance is related to the peak-to-peak inductor ripple current, the input and the output voltages (for 300kHz operation): (4) A higher value of ripple current reduces inductance, but increases the conductance loss, core loss, and current stress for the inductor and switch devices.
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LM2717 SNVS253D – MAY 2005 – REVISED MARCH 2013 www.ti.com LAYOUT CONSIDERATIONS The LM2717 uses two separate ground connections, PGND for the drivers and boost NMOS power device and AGND for the sensitive analog control circuitry. The AGND and PGND pins should be tied directly together at the package. The feedback and compensation networks should be connected directly to a dedicated analog ground plane and this ground plane must connect to the AGND pin.
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LM2717 www.ti.com SNVS253D – MAY 2005 – REVISED MARCH 2013 L1 22 PH CBOOT1 4.7 nF U1 CSS1 CC1 47 nF 20k 4.7 nF RC1 CBG 1 nF CC2 2k 4.7 nF RC2 CSS2 RF 20.5k 47 nF AGND CB1 SW1 FB1 SHDN1 SS1 VC1 VIN VBG VIN VC2 SHDN2 CB2 *Connect CINA (pin 23) and CINB (pins 14,15) as close as possible to the VIN pins. VIN SS2 FSLCT FB2 AGND AGND SW2 PGND AGND PGND PGND PGND CBOOT2 *CINB 4.7 PF ceramic 3.3V OUT1 D1 MBRS240 COUT1A 1 PF ceramic 17V to 20V IN *CINA 4.
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LM2717 SNVS253D – MAY 2005 – REVISED MARCH 2013 www.ti.com REVISION HISTORY Changes from Revision C (March 2013) to Revision D • 12 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 23-Sep-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device LM2717MTX/NOPB Package Package Pins Type Drawing TSSOP PW 24 SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) 2500 330.0 16.4 Pack Materials-Page 1 6.95 B0 (mm) K0 (mm) P1 (mm) 8.3 1.6 8.0 W Pin1 (mm) Quadrant 16.
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PACKAGE MATERIALS INFORMATION www.ti.com 23-Sep-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM2717MTX/NOPB TSSOP PW 24 2500 367.0 367.0 35.
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