LM2618BTL Datasheet PDF - National Semiconductor
| Part Number | LM2618BTL | |
| Description | 400mA Sub-miniature/ High Efficiency/ Synchronous PWM & PFM Programmable DC-DC Converter | |
| Manufacturers | National Semiconductor | |
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September 2002
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.
Key Specifications
n Operates from a single LiION cell (2.8V to 5.5V)
n Internal synchronous rectification provides high
efficiency in both PWM and PFM
n Pin programmable output voltage (1.80V, 1.83V, 1.87V
and 1.92V)
n 400mA maximum load capability (300mA for B grade)
n ±2% PWM mode DC output voltage precision
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
(91% at 3.0VIN, 1.92VOUT)
n 600kHz PWM mode switching frequency
n SYNC input for PWM mode frequency synchronization
from 500kHz to 1MHz
Features
n Sub-miniature 10-pin micro SMD package
n Only three tiny surface-mount external components
required
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
Typical Application Circuit
© 2002 National Semiconductor Corporation DS200364
20036402
www.national.com
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Electrical Characteristics (Continued)
Specifications with standard typeface are for TA = TJ = 25˚C, and those in bold face type apply over the full Operating Tem-
perature Range (TA = TJ = - 25˚C to +85˚C). Unless otherwise specified, PVIN = VDD = EN = SYNC = 3.6V, VID0 = VID1 =
0V.
Symbol
Parameter
Conditions
Min
Typ
Max
Units
FSYNC
SYNC/MODE Clock
Frequency Range
(Note 8)
500
1000
kHz
FOSC
Internal Oscillator
Frequency
LM2618ATL, PWM Mode
(SYNC = VIN)
LM2618BTL, PWM Mode
(SYNC = VIN)
468 600 732
kHz
450 600 750
Tmin
Minimum ON-Time of P FET
Switch in PWM Mode
200 ns
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings are conditions for which the device is intended
to be functional, but parameter specifications may not be guaranteed. For guaranteed specifications and associated test conditions, see the Min and Max limits and
Conditions in the Electrical Characteristics table. Electrical Characteristics table limits are guaranteed by production testing, design or correlation using standard
Statistical Quality Control methods. Typical (Typ) specifications are mean or average values from characterization at 25˚C and are not guaranteed.
Note 2: In PWM mode, Thermal shutdown will occur if the junction temperature exceeds the 150˚C maximum junction temperature of the device.
Note 3: Thermal resistance specified with 2 layer PCB(0.5/0.5 oz. cu).
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.
Although the LM2618 exhibits safe behavior while enabled at low input voltages, this is not guaranteed.
Note 5: The feedback voltage is trimmed at the 1.87V output setting. The other output voltages result from the pin selection of the internal DAC’s divider ratios. The
precision for the feedback voltages is ±2%.
Note 6: : The hysteresis voltage is the minimum voltage swing on FB that causes the internal feedback and control circuitry to turn the internal PFET switch on and
then off during PFM mode.
Note 7: Current limit is built-in, fixed, and not adjustable. If the current limit is reached while the output is pulled below about 0.7V, the internal PFET switch turns
off for 2.5 µs to allow the inductor current to diminish.
Note 8: SYNC driven with an external clock switching between VDD and GND. When an external clock is present at SYNC, the IC is forced to PWM mode at the
external clock frequency. The LM2618 synchronizes to the rising edge of the external clock.
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| Information | Total 15 Pages | |
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