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CON

2.7V to 5.5V

OUT

0.8V to 3.6V

10 PF

4.7 PF

SGNDPGND

3.3 PH

LM3208

OUT

= 2.5 x V

CON

LM3208

www.ti.com

SNVS404B –APRIL 2006–REVISED MARCH 2013

LM3208 650mA Miniature, Adjustable, Step-Down DC-DC Converter for RF Power

Amplifiers

Check for Samples: LM3208

FEATURES

DESCRIPTION

The LM3208 is a DC-DC converter optimized for

• 2 MHz (typ.) PWM Switching Frequency

powering RF power amplifiers (PAs) from a single

• Operates from a Single Li-Ion Cell (2.7V to

Lithium-Ion cell. However, it may be used in many

5.5V)

other applications. It steps down an input voltage in

• Adjustable Output Voltage (0.8V to 3.6V)

the range from 2.7V to 5.5V to an adjustable output

voltage of 0.8V to 3.6V. Output voltage is set by

• Fast Output Voltage Transient (0.8V to 3.4V in

using a V

CON

analog input to control power levels and

25µs typ.)

efficiency of the RF PA.

• 650mA Maximum Load Capability

The LM3208 offers superior performance for mobile

• High Efficiency (95% typ. at 3.9V

, 3.4V

OUT

phones and similar RF PA applications. Fixed-

400mA)

frequency PWM operation minimizes RF interference.

• 8-pin DSBGA Package

A shutdown function turns the device off and reduces

battery consumption to 0.01 µA (typ.).

• Current Overload Protection

• Thermal Overload Protection

The LM3208 is available in an 8-pin lead-free DSBGA

package. A high switching frequency (2 MHz typ.)

allows use of tiny surface-mount components. Only

APPLICATIONS

three small external surface-mount components, an

• Cellular Phones

inductor and two ceramic capacitors, are required.

• Hand-Held Radios

• RF PC Cards

• Battery Powered RF Devices

TYPICAL APPLICATION

Figure 1. LM3208 Typical Application

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 (25 pages)

PAGE 1
LM3208 www.ti.com SNVS404B – APRIL 2006 – REVISED MARCH 2013 LM3208 650mA Miniature, Adjustable, Step-Down DC-DC Converter for RF Power Amplifiers Check for Samples: LM3208 FEATURES DESCRIPTION • • The LM3208 is a DC-DC converter optimized for powering RF power amplifiers (PAs) from a single Lithium-Ion cell. However, it may be used in many other applications. It steps down an input voltage in the range from 2.7V to 5.5V to an adjustable output voltage of 0.8V to 3.6V.
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LM3208 SNVS404B – APRIL 2006 – REVISED MARCH 2013 www.ti.com CONNECTION DIAGRAMS SW SW A2 A2 PVIN A1 A3 PGND PGND A3 A1 PVIN VDD B1 B3 SGND SGND B3 B1 VDD C3 FB EN C1 C1 EN FB C3 C2 C2 VCON VCON Top View Bottom View Figure 2. 8-Bump Thin DSBGA Package, Large Bump Package Number YZR0008GNA PIN DESCRIPTIONS Pin # Name A1 PVIN Power Supply Voltage Input to the internal PFET switch. Description B1 VDD Analog Supply Input. C1 EN Enable Input.
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LM3208 www.ti.com SNVS404B – APRIL 2006 – REVISED MARCH 2013 ABSOLUTE MAXIMUM RATINGS (1) (2) (3) −0.2V to +6.0V VDD, PVIN to SGND −0.2V to +0.2V PGND to SGND (SGND − 0.2V) to (VDD + 0.2V) w/6.0V max EN, FB, VCON (PGND − 0.2V) to (PVIN + 0.2V) w/6.0V max SW −0.2V to +0.
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LM3208 SNVS404B – APRIL 2006 – REVISED MARCH 2013 www.ti.com ELECTRICAL CHARACTERISTICS (1) (2) (3) Limits in standard typeface are for TA = TJ = 25°C. Limits in boldface type apply over the full operating ambient temperature range (−30°C ≤ TA = TJ ≤ +85°C). Unless otherwise noted, all specifications apply to the LM3208 with: PVIN = VDD = EN = 3.6V. Symbol Parameter Conditions VFB, MIN Feedback Voltage at minimum setting VCON = 0.32V (3) VFB, MAX Feedback Voltage at maximum setting VCON = 1.
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LM3208 www.ti.com SNVS404B – APRIL 2006 – REVISED MARCH 2013 SYSTEM CHARACTERISTICS The following spec table entries are specified by design providing the component values in the typical application circuit are used (L = 3.0µH, DCR = 0.12Ω, FDK MIPW3226D3R0M; CIN = 10µF, 6.3V, 0805, TDK C2012X5R0J106K; COUT = 4.7µF, 6.3V, 0603, TDK C1608X5R0J475M). These parameters are not specified by production testing. Min and Max values are specified over the ambient temperature range TA = −30°C to 85°C.
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LM3208 SNVS404B – APRIL 2006 – REVISED MARCH 2013 www.ti.com TYPICAL PERFORMANCE CHARACTERISTICS Quiescent Current vs Supply Voltage (VCON = 0V, FB = 0V, No Switching) Shutdown Current vs Temperature (VCON = 0V, EN = 0V) Figure 3. Figure 4. Switching Frequency vs Temperature (VOUT = 1.3V, IOUT = 200mA) Output Voltage vs Supply Voltage (VOUT = 1.3V) 3 1.312 VIN = 5.5V IOUT = 50 mA 2 1.310 OUTPUT VOLTAGE (V) SWITCHING FREQUENCY VARIATION (%) (Circuit in Figure 35, PVIN = VDD = EN = 3.
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LM3208 www.ti.com SNVS404B – APRIL 2006 – REVISED MARCH 2013 TYPICAL PERFORMANCE CHARACTERISTICS (continued) (Circuit in Figure 35, PVIN = VDD = EN = 3.6V and TA = 25°C unless otherwise specified.). 4.0 Current Limit vs Temperature (Large PFET) Current Limit vs Temperature (Small PFET) Figure 9. Figure 10. VCON Voltage vs Output Voltage (RLOAD = 10 Ω) VCON Voltage vs Output Voltage (RLOAD = 10 Ω) 1.0 VIN = 4.7V TA = -30ºC, 25ºC, 85ºC VIN = 3.6V, 4.2V, 4.7V, 5.
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LM3208 SNVS404B – APRIL 2006 – REVISED MARCH 2013 www.ti.com TYPICAL PERFORMANCE CHARACTERISTICS (continued) (Circuit in Figure 35, PVIN = VDD = EN = 3.6V and TA = 25°C unless otherwise specified.). Efficiency vs Output Current (VOUT = 0.8V) Efficiency vs Output Current (VOUT = 3.6V) 100 VIN = 3.9V 98 EFFICIENCY (%) 96 94 92 90 VIN = 4.5V 88 86 VIN = 5.5V 84 82 80 0 0 100 200 300 400 500 600 700 OUTPUT CURRENT (mA) Figure 15. Figure 16.
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LM3208 www.ti.com SNVS404B – APRIL 2006 – REVISED MARCH 2013 TYPICAL PERFORMANCE CHARACTERISTICS (continued) (Circuit in Figure 35, PVIN = VDD = EN = 3.6V and TA = 25°C unless otherwise specified.). RDSON vs Temperature (N-ch, ISW = –200mA) VIN-VOUT vs Output Current (100% Duty Cycle) Figure 21. Figure 22. Load Transient Response (VOUT = 0.8V) Load Transient Response (VIN = 4.2V, VOUT = 3.4V) 50 mV/DIV AC Coupled VOUT 100 mV/DIV AC Coupled VOUT VIN = 3.6V VIN = 4.2V VOUT = 0.8V VOUT = 3.
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LM3208 SNVS404B – APRIL 2006 – REVISED MARCH 2013 www.ti.com TYPICAL PERFORMANCE CHARACTERISTICS (continued) (Circuit in Figure 35, PVIN = VDD = EN = 3.6V and TA = 25°C unless otherwise specified.). Shutdown Response (VIN = 4.2V, VOUT = 3.4V, RLOAD = 10Ω) Line Transient Reponse (VIN = 3.0V to 3.6V, IOUT = 100mA) Figure 27. Figure 28. VCON Transient Response (VIN = 4.2V, VCON = 0.32V/1.44V, RLOAD = 10Ω) Timed Current Limit Response (VIN = 3.6V) Figure 29. Figure 30. Output Voltage Ripple (VOUT = 1.
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LM3208 www.ti.com SNVS404B – APRIL 2006 – REVISED MARCH 2013 TYPICAL PERFORMANCE CHARACTERISTICS (continued) (Circuit in Figure 35, PVIN = VDD = EN = 3.6V and TA = 25°C unless otherwise specified.). Output Voltage Ripple (VOUT = 3.4V) Output Voltage Ripple in Pulse Skip (VIN = 3.96V, VOUT = 3.4V, RLOAD = 5Ω) Figure 32. Figure 33.
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LM3208 SNVS404B – APRIL 2006 – REVISED MARCH 2013 www.ti.com BLOCK DIAGRAM VDD PVIN SMALL LARGE PFET PFET VCON DELAY LOGIC ERROR AMPLIFIER FB CURRENT COMP OSCILLATOR FET SIZE CONTROL COMP EN SW MOSFET CONTROL LOGIC MAIN CONTROL SHUTDOWN CONTROL PGND GND Figure 34. Functional Block Diagram OPERATION DESCRIPTION The LM3208 is a simple, step-down DC-DC converter optimized for powering RF power amplifiers (PAs) in mobile phones, portable communicators, and similar battery powered RF devices.
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LM3208 www.ti.com SNVS404B – APRIL 2006 – REVISED MARCH 2013 VIN 2.7V to 5.5V C1* 10 PF PVIN VDD L1 3.3 PH VOUT 0.8V to 3.6V SW SYSTEM DAC CONTROLLER ON/OFF VCON LM3208 FB C2 4.7 PF EN SGND PGND * Place C1 close to PVIN Figure 35. Typical Operating System Circuit Circuit Operation Referring to Figure 1 and Figure 34, the LM3208 operates as follows. During the first part of each switching cycle, the control block in the LM3208 turns on the internal PFET (P-channel MOSFET) switch.
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LM3208 SNVS404B – APRIL 2006 – REVISED MARCH 2013 www.ti.com Internal Synchronous Rectification While in PWM mode, the LM3208 uses an internal NFET as a synchronous rectifier to reduce rectifier forward voltage drop and associated power loss. Synchronous rectification provides a significant improvement in efficiency whenever the output voltage is relatively low compared to the voltage drop across an ordinary rectifier diode.
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LM3208 www.ti.com SNVS404B – APRIL 2006 – REVISED MARCH 2013 If VCON is over 1.44V (VOUT = 3.6V), sub-harmonic oscillation may occur because of insufficient slope compensation. If VCON voltage is less than 0.32V (VOUT = 0.8V), the output voltage may not be regulated due to the required on-time being less than the minimum on-time (55ns). The output voltage can go lower than 0.8V providing a limited VIN range is used. Refer to datasheet curve (VCON Voltage vs Output Voltage) for details.
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LM3208 SNVS404B – APRIL 2006 – REVISED MARCH 2013 www.ti.com If a smaller inductance inductor is used in the application, the LM3208 may become unstable during line and load transients, and VCON transient response times may be affected. For low-cost applications, an unshielded bobbin inductor is suggested. For noise-critical applications, a toroidal or shielded-bobbin inductor should be used. A good practice is to lay out the board with footprints accommodating both types for design flexibility.
PAGE 17
LM3208 www.ti.com SNVS404B – APRIL 2006 – REVISED MARCH 2013 The 8-Bump package used for LM3208 has 300micron solder balls and requires 10.82mil pads for mounting on the circuit board. The trace to each pad should enter the pad with a 90°entry angle to prevent debris from being caught in deep corners. Initially, the trace to each pad should be 7mil wide, for a section approximately 7mil long, as a thermal relief. Then each trace should neck up or down to its optimal width.
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LM3208 SNVS404B – APRIL 2006 – REVISED MARCH 2013 www.ti.com 3.0 ÛH 4.7 ÛF 10 ÛF Figure 37. Evaluation Board Layout Board Layout Flow 1. Minimize C1, PVIN, and PGND loop. These traces should be as wide and short as possible. This is the highest priority. 2. Minimize L1, C2, SW and PGND loop. These traces also should be wide and short. This is the second priority. 3.
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LM3208 www.ti.
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LM3208 SNVS404B – APRIL 2006 – REVISED MARCH 2013 www.ti.com REVISION HISTORY Changes from Revision A (March 2013) to Revision B • 20 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 26-Mar-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) LM3208TL/NOPB DSBGA YZR 8 250 178.0 8.4 LM3208TLX/NOPB DSBGA YZR 8 3000 178.0 8.4 Pack Materials-Page 1 B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant 1.85 2.01 0.76 4.0 8.0 Q1 1.85 2.01 0.76 4.0 8.
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PACKAGE MATERIALS INFORMATION www.ti.com 26-Mar-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM3208TL/NOPB DSBGA YZR LM3208TLX/NOPB DSBGA YZR 8 250 210.0 185.0 35.0 8 3000 210.0 185.0 35.
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MECHANICAL DATA YZR0008xxx D 0.600±0.075 E TLA08XXX (Rev C) D: Max = 1.862 mm, Min =1.802 mm E: Max = 1.712 mm, Min =1.652 mm 4215045/A NOTES: A. All linear dimensions are in millimeters. Dimensioning and tolerancing per ASME Y14.5M-1994. B. This drawing is subject to change without notice. www.ti.
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