lm2618 National Semiconductor Corporation, lm2618 Datasheet

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lm2618

Manufacturer Part Number
lm2618
Description
400ma Sub-miniature, High Efficiency, Synchronous Pwm & Pfm Programmable Dc-dc Converter
Manufacturer
National Semiconductor Corporation
Datasheet

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lm2618ATL
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lm2618BTL
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© 2002 National Semiconductor Corporation
LM2618
400mA Sub-miniature, High Efficiency, Synchronous
PWM & PFM Programmable DC-DC Converter
General Description
The LM2618 step-down DC-DC converter is optimized for
powering low voltage circuits from a single Lithium-Ion cell. It
provides up to 400mA (300mA for B grade), over an input
voltage range of 2.8V to 5.5V. Pin programmable output
voltages of 1.80V, 1.83V, 1.87V or 1.92V allow adjustment
for MPU voltage options without board redesign or external
feedback resistors. Internal synchronous rectification pro-
vides high efficiency in both PWM and PFM operation.
The device has three pin-selectable modes for maximizing
battery life in mobile phones and similar portable applica-
tions. Low-noise PWM mode offers 600kHz fixed-frequency
operation to reduce interference in RF and data acquisition
applications during full-power operation. A SYNC input al-
lows synchronizing the switching frequency in a range of
500kHz to 1MHz to avoid noise from intermodulation with
system frequencies. Low-current hysteretic PFM mode re-
duces quiescent current to 180 µA (typ.) during system
standby. Shutdown mode turns the device off and reduces
battery consumption to 0.02µA (typ.). Additional features
include soft start and current overload protection.
The LM2618 is available in a 10 pin micro SMD packge. This
package uses National’s wafer level chip-scale micro SMD
technology and offers the smallest possible size. Only three
small external surface-mount components, an inductor and
two ceramic capacitors are required.
Typical Application Circuit
DS200364
Key Specifications
n Operates from a single LiION cell (2.8V to 5.5V)
n Internal synchronous rectification provides high
n Pin programmable output voltage (1.80V, 1.83V, 1.87V
n 400mA maximum load capability (300mA for B grade)
n
n 5mV typ PWM mode output voltage ripple
n 180 µA typ PFM mode quiescent current
n 0.02µA typ shutdown mode current
n Internal synchronous rectification for high efficiency
n 600kHz PWM mode switching frequency
n SYNC input for PWM mode frequency synchronization
Features
n Sub-miniature 10-pin micro SMD package
n Only three tiny surface-mount external components
n Uses small ceramic capacitors.
n Internal soft start
n Current overload protection
n Thermal Shutdown Protection
n No external compensation required
Applications
n Mobile Phones
n Hand-Held Radios
n Battery Powered Devices
efficiency in both PWM and PFM
and 1.92V)
(91% at 3.0V
from 500kHz to 1MHz
required
±
2% PWM mode DC output voltage precision
IN
, 1.92V
OUT
)
20036402
September 2002
www.national.com

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lm2618 Summary of contents

Page 1

... Shutdown mode turns the device off and reduces battery consumption to 0.02µA (typ.). Additional features include soft start and current overload protection. The LM2618 is available pin micro SMD packge. This package uses National’s wafer level chip-scale micro SMD technology and offers the smallest possible size. Only three small external surface-mount components, an inductor and two ceramic capacitors are required ...

Page 2

... SMD LM2618ATL LM2618BTL 10-bump Wafer Level Chip Scale (micro SMD) LM2618ATLX LM2618BTLX (*) XY - denotes the date code marking (2 digit) in production (*) TT - refers to die run/lot traceability for production (*) I - pin one indication (*) S - Product line designator Note that Package Marking may change over the course of production www ...

Page 3

... SW Switching Node connection to the internal PFET switch and NFET synchronous rectifier. Connect to an inductor with a saturation current rating that exceeds the max Switch Peak Current Limit specification of the LM2618 (Figure 1) B3 PVIN Power Supply Input to the internal PFET switch. Connect to the input filter capacitor (Figure 1) ...

Page 4

... Minimum ESD Rating −0.2V to +6V Human body model 100pF 1.5 kΩ −0.2V to +0.2V Thermal Resistance (θ LM2618ATL & LM2618BTL (Note 3) −0.2V to +6V (GND −0.2V) to (VDD +0.2V) −45˚C to +150˚ 25˚C, and those in bold face type apply over the full Operating Tem- ...

Page 5

... Note 4: The LM2618 is designed for cell phone applications where turn-on after power-up is controlled by the system processor and internal UVLO (Under Voltage LockOut) circuitry is unecessary. The LM2618 has no UVLO circuitry and should be kept in shutdown by holding the EN pin low until the input voltage exceeds 2.8V. ...

Page 6

... Typical Operating Characteristics µH, unless otherwise noted. Quiescent Supply Current vs Temperature (V =1.8V) OUT Shutdown Quiescent Current vs Temperature Output Voltage vs Temperature (V = 1.8V, PFM Mode) OUT www.national.com LM2618ATL, Circuit of Figure 1, V Quiescent Supply Current vs Supply Voltage 20036406 Output Voltage vs Temperature ( V 20036421 Output Voltage vs Supply Voltage (V OUT 20036407 6 = 3.6V 25˚ ...

Page 7

... Output Voltage vs Supply Voltage (V = 1.8V, PFM Mode) OUT Output Voltage vs Output Current (V = 1.8V, PFM Mode) OUT Efficiency vs Output Current (V = 1.8V, PFM Mode) OUT LM2618ATL, Circuit of Figure 1, V Output Voltage vs Output Current (V OUT 20036419 Efficiency vs Output Current (V OUT 20036420 Switching Frequency vs Temperature 20036424 7 = 3.6V 25˚ ...

Page 8

... Typical Operating Characteristics unless otherwise noted. (Continued) PWM to PFM Response Load Transient Response (PWM Mode) Line Transient Response (PWM Mode) www.national.com LM2618ATL, Circuit of Figure 1, V Shutdown Response (PWM Mode) 20036413 Load Transient Response (PFM Mode) 20036412 20036416 8 = 3.6V 25˚ µH, ...

Page 9

... Shutdown mode turns the device off and reduces battery consumption to 0.02µA (typ.). The LM2618 offers good performance and a full set of fea- tures based on a current-mode switching buck architecture. The SYNC/MODE input accepts an external clock between 500kHz and 1MHz ...

Page 10

... Circuit Operation (Continued) PWM Operation The LM2618 can be set to current-mode PWM operation by connecting the SYNC/MODE pin to VDD. While in PWM (Pulse Width Modulation) mode, the output voltage is regu- lated by switching at a constant frequency and then modu- lating the energy per cycle to control power to the load. ...

Page 11

... LM2618 are turned off. Setting EN high to VDD enables normal operation. While turning on, soft start is activated. EN must be set low to turn off the LM2618 during undervolt- age conditions when the supply is less than the 2.8V mini- mum operating voltage. The LM2618 is designed for mobile ...

Page 12

... Current Limiting A current limit feature allows the LM2618 to protect itself and external components during overload conditions. Current limiting is implemented using an independent internal com- parator. In PWM mode, cycle-by-cycle current limiting is normally used excessive load pulls the output voltage down to approximately 0.7V, then the device switches to a timed current limit mode ...

Page 13

... The input filter capacitor supplies current to the PFET switch of the LM2618 in the first part of each cycle and reduces voltage ripple imposed on the input power source. The out- put filter capacitor smoothes out current flow from the induc- tor to the load, helps maintain a steady output voltage during transient load changes and reduces output voltage ripple ...

Page 14

... Connect the ground pins of the LM2618 and filter ca- pacitors together using generous component-side cop- per fill as a pseudo-ground plane. Then, connect this to the ground-plane (if one is used) with several vias ...

Page 15

... NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant ...

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