Specifications

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LM2614

400mA Sub-Miniature Adjustable DC-DC Converter

Optimized for RF Power Amplifiers

General Description

The LM2614 DC-DC converter is optimized for powering RF

power amplifiers (PAs) from a single Lithium-Ion cell. It steps

down an input voltage of 2.8V to 5.5V to an output of 1.0V to

3.6V at up to 400mA (300mA for B grade). Output voltage is

set using an analog input to VCON in the application circuit.

The device offers three modes for mobile phones and similar

RF PA applications. Fixed-frequency PWM mode minimizes

RF interference. A SYNC input allows synchronizing the

switching frequency in a range of 500kHz to 1MHz. Low

current hysteretic PFM mode reduces quiescent current to

160µA (typ.). Shutdown mode turns the device off and re-

duces battery consumption to 0.02µA (typ.).

Current limit and thermal shutdown features protect the de-

vice and system during fault conditions.

The LM2614 is available in a 10 bump micro SMD package.

This packaging uses National’s chip-scale micro SMD tech-

nology and offers the smallest possible size. A high switching

frequency (600kHz) allows use of tiny surface-mount com-

ponents.

The LM2614 can be dynamically controlled for output volt-

age changes from 1.0V to 3.6V in

30µs. The device fea-

tures external compensation to tailor the response to a wide

range of operating conditions.

Key Specifications

n Operates from a single LiION cell (2.8V to 5.5V)

n Adjustable output voltage (1.0V to 3.6V)

1% DC feedback voltage precision

n 400mA maximum load capability(300mA for B grade)

n 600µA typ PWM mode quiescent current

n 0.02µA typ shutdown current

n 600kHz PWM switching frequency

n SYNC input for PWM mode frequency synchronization

from 500kHz to 1MHz

n High efficiency (96% typ at 3.9V

, 3.6V

OUT

and 200mA)

in PWM mode from internal synchronous rectification

n 100% Maximum Duty Cycle for Lowest Dropout

Features

n Sub-miniature 10-bump thin micro SMD package

n Uses small ceramic capacitors

n 5mV typ PWM mode output voltage ripple(C

OUT

= 22µF)

n Internal soft start

n Current overload protection

n Thermal Shutdown

n External compensation

Applications

n Mobile Phones

n Hand-Held Radios

n RF PC Cards

n Battery Powered RF Devices

August 2002

LM2614 400mA Sub-Miniature Adjustable DC-DC Converter Optimized for RF Power Amplifiers

Summary of content (16 pages)

PAGE 1
LM2614 400mA Sub-Miniature Adjustable DC-DC Converter Optimized for RF Power Amplifiers General Description Key Specifications The LM2614 DC-DC converter is optimized for powering RF power amplifiers (PAs) from a single Lithium-Ion cell. It steps down an input voltage of 2.8V to 5.5V to an output of 1.0V to 3.6V at up to 400mA (300mA for B grade). Output voltage is set using an analog input to VCON in the application circuit. The device offers three modes for mobile phones and similar RF PA applications.
PAGE 2
LM2614 Typical Application Circuits 20036701 FIGURE 1. Typical Circuit for Powering RF Power Amplifiers 20036702 FIGURE 2. Typical Circuit for 2.5V Output Voltage 20036703 FIGURE 3. Typical Circuit for 1.5V Output Voltage www.national.
PAGE 3
LM2614 Connection Diagrams 10-Bump micro SMD Package 20036704 20036705 Top View Bottom View Ordering Information Order Number Package Type NSC Package Marking (*) LM2614ATL LM2614BTL LM2614ATLX 10-bump Wafer Level Chip Scale (micro SMD) LM2614BTLX Supplied As XYTT S50A 250 Tape and Reel XYTT S50B 250 Tape and Reel XYTT S50A 3000 Tape and Reel XYTT S50B 3000 Tape and Reel (*) XY - denotes the date code marking (2 digit) in production (*) TT - refers to die run/lot traceability for produc
PAGE 4
LM2614 Absolute Maximum Ratings (Note 1) Storage Temperature Range Lead Temperature (Soldering, 10 sec.) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. PVIN, VDD to SGND EN, EAOUT, EANEG, SYNC/MODE to SGND FB, SW 260˚C Junction Temperature (Note 2) −0.2V to +6V PGND to SGND, PVIN to VDD −45˚C to +150˚C −25˚C to +125˚C ± 2 kV Minimum ESD Rating −0.2V to +0.
PAGE 5
LM2614 Typical Performance Characteristics LM2614ATL, Circuit of Figure 4, VIN = 3.6V, TA = 25˚C, unless otherwise noted. Shutdown Quiescent Current vs Temperature (Circuit in Figure 3) Quiescent Supply Current vs Supply Voltage 20036708 20036722 Output Voltage vs Supply Voltage (VOUT = 1.5V, PWM MODE) Output Voltage vs Supply Voltage (VOUT = 1.0V, PWM MODE) 20036724 20036709 Output Voltage vs Output Current (VOUT = 1.5V, PWM MODE) Output Voltage vs Output Current (VOUT = 1.
PAGE 6
LM2614 Typical Performance Characteristics LM2614ATL, Circuit of Figure 4, VIN = 3.6V, TA = 25˚C, unless otherwise noted. (Continued) Output Voltage vs Output Current (VOUT = 3.6V, PWM MODE) Dropout Voltage vs Output Current (VOUT = 3.6V, PWM MODE) 20036732 20036712 Switching Frequency vs Temperature (Circuit in Figure 3, PWM MODE) Feedback Bias Current vs Temperature (Circuit in Figure 3) 20036723 20036731 Efficiency vs Output Current (VOUT = 1.
PAGE 7
LM2614 Typical Performance Characteristics LM2614ATL, Circuit of Figure 4, VIN = 3.6V, TA = 25˚C, unless otherwise noted. (Continued) Efficiency vs Output Current (VOUT = 1.5V, PWM MODE) Efficiency vs Output Current (VOUT = 1.5V, PWM MODE, with Diode) 20036715 20036716 Efficiency vs Output Current (VOUT = 3.6V, PWM MODE, with Diode) Efficiency vs Output Current (VOUT = 3.6V, PWM MODE) 20036717 20036718 7 www.national.
PAGE 8
LM2614 Typical Performance Characteristics LM2614ATL, Circuit of Figure 4, VIN = 3.6V, TA = 25˚C, unless otherwise noted. (Continued) Efficiency vs Output Voltage (PWM MODE, with Diode) 20036730 3.9V input. The efficiency can be further increased by using a schottky diode like MBRM120 as shown in Figure 4. PWM mode quiescent current is 600µA typ. The output voltage is dynamically programmable from 1.0V to 3.6V by adjusting the voltage on the VCON at the external feedback resistors.
PAGE 9
LM2614 Device Information (Continued) 20036706 FIGURE 4. Typical Operating Circuit transferred back into the circuit and depleted, the inductor current ramps down with a slope of VOUT/L. If the inductor current reaches zero before the next cycle, the synchronous rectifier is turned off to prevent current reversal. The output filter capacitor stores charge when the inductor current is high, and releases it when low, smoothing the voltage across the load.
PAGE 10
LM2614 Device Information (Continued) PFM Mode Switching Waveform PWM OPERATION While in PWM (Pulse Width Modulation) mode, the output voltage is regulated by switching at a constant frequency and then modulating the energy per cycle to control power to the load. Energy per cycle is set by modulating the PFET switch on-time pulse-width to control the peak inductor current.
PAGE 11
EN should be set low to turn off the LM2614 during system power-up and undervoltage conditions when the supply is less than the 2.8V minimum operating voltage. The LM2614 is designed for compact portable applications, such as mobile phones. In such applications, the system controller determines power supply sequencing. Although the LM2614 is typically well behaved at low input voltages, this is not guaranteed. (Continued) extending battery life when the load is in a low-power standby mode.
PAGE 12
LM2614 Device Information (Continued) Load Transient Response (Circuit in Figure 3) VCON Transient Response (Circuit in Figure 4) 20036727 20036719 FIGURE 10. FIGURE 8. Line Transient Response (Circuit in Figure 3) VCON Transient Response in Dropout (Circuit in Figure 4) 20036728 20036720 FIGURE 11. FIGURE 9. SOFT-START The LM2614 has soft start to reduce current inrush during power-up and startup. This reduces stress on the LM2614 and external components.
PAGE 13
SETTING THE OUTPUT VOLTAGE The LM2614 can be used with external feedback resistors and an analog signal to vary the output voltage. Select an output voltage from 1.0V to 3.6V by setting the voltage on the VCON as directed in Table 1. EXTERNAL COMPENSATION The LM2614 uses external components connected to the EANEG and EAOUT pins to compensate the regulator (Figure 4). Typically, all that is required is a series connection of one capacitor (C4) and one resistor (R3).
PAGE 14
LM2614 Application Information and/or increased tolerance to heavy load transients. A 10µF ceramic output capacitor can be used in applications where the worst case load transient step is less than 200mA. Table 3 lists suggested capacitors and suppliers. The input filter capacitor supplies current to the PFET switch of the LM2614 in the first part of each cycle and reduces voltage ripple imposed on the input power source.
PAGE 15
reduces voltage errors caused by resistive losses across the traces. (Continued) 3. Arrange the components so that the switching current loops curl in the same direction. During the first half of each cycle, current flows from the input filter capacitor, through the LM2614 and inductor to the output filter capacitor and back through ground, forming a current loop.
PAGE 16
LM2614 400mA Sub-Miniature Adjustable DC-DC Converter Optimized for RF Power Amplifiers Physical Dimensions inches (millimeters) unless otherwise noted NOTES: UNLESS OTHERWISE SPECIFIED 1. EPOXY COATING 2. 63Sn/37Pb EUTECTIC BUMP 3. RECOMMEND NON-SOLDER MASK DEFINED LANDING PAD. 4. PIN A1 IS ESTABLISHED BY LOWER LEFT CORNER WITH RESPECT TO TEXT ORIENTATION. 5. XXX IN DRAWING NUMBER REPRESENTS PACKAGE SIZE VARIATION WHERE X1 IS PACKAGE WIDTH, X2 IS PACKAGE LENGTH AND X3 IS PACKAGE HEIGHT. 6.