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PDF LM3280 Data sheet ( Hoja de datos )
| Número de pieza | LM3280 | |
| Descripción | Adjustable Step-Down DC-DC Converter and 3 LDOs | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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January 2007
LM3280
Adjustable Step-Down DC-DC Converter and 3 LDOs for RF
Power Management
General Description
The LM3280 is a multi-functional Power Management Unit,
optimized for low-power handheld applications such as Cel-
lular Phones.
The LM3280 incorporates three low-dropout LDO voltage
regulators and one step down PWM DC-DC converter with an
internal Bypass FET. The step down converter's output volt-
age can be set using an analog input (VCON) for optimizing
efficiency of the RF PA at various power levels. The LDO op-
erates a nominal output voltage of 2.85V and maximum load
current capability of 20mA for a reference voltage required by
linear RF power amplifiers. The LM3280 additionally features
a separate enable pin for each output.
The LM3280 is available in a 16-pin lead free micro SMD
package.
Features
■ 2MHz (typ.) PWM Switching Frequency
■ Operates from a single Li-Ion cell (2.7V to 5.5V)
■ Adjustable Output Voltage (0.8V to 3.6V) DC-DC
■ High-efficiency synchronous buck converter
■ 300mA Maximum load capability (PWM mode)
■ 500mA Maximum load capability (Bypass mode)
■ PWM, Forced and Automatic Bypass Mode
■ 3 Low-dropout and fast transient response LDOs
■ 16-pin micro SMD Package
■ Current Overload Protection
■ Thermal Overload Protection
Applications
■ Cellular Phones
■ Hand-Held Radios
■ Battery Powered RF Devices
Typical Application
FIGURE 1. LM3280 Typical Application
© 2007 National Semiconductor Corporation 201819
20181901
www.national.com
1 page  
Buck Electrical Characteristics (Notes 2, 7) 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,
specifications apply to the LM3280 with: VIN = ( SVIN = PVIN = ) 3.6V, ENBUCK = 3.6V, ENLDO1 = ENLDO2 = ENLDO3 = BYP = 0V,
FB = 2V, VCON = 0.267V.
Symbol
Parameter
Conditions
Min.
Typ.
Max
Units
VFB_ MIN
VFB_ MAX
OVP
Feedback Voltage at Minimum Setting VCON = 0.267V
Feedback Voltage at Maximum Setting VCON = 1.20V, VIN = 4.2V
Over-Voltage Protection Threshold (Note 9)
0.75
3.528
0.800
3.600
330
0.85
3.672
400
V
V
mV
VBYPASS−
Auto Bypass Detection Negative
Threshold
(Note 10)
160 250
320
mV
VBYPASS+
Auto Bypass Detection Positive
Threshold
(Note 10)
350 450
540
mV
RDSON (P)
RDSON (N)
RDSON (BYP)
ILIM-PWM
ILIM-BYP
FOSC
Gain
Pin-Pin Resistance for PFET
Pin-Pin Resistance for N-FET
Pin-Pin Resistance for Bypass FET
Switch Current Limit
Bypass FET Current Limit
Internal Oscillator Frequency
VCON to VOUT Gain
ICON
VCON Input Leakage Current
ISW = 500mA, FB = 0V
ISW = - 200mA
IBYPOUT = 500mA
FB = 0V (Note 12)
(Note 13)
0.267V ≤ VCON ≤ 1.20V,
VIN = 4.2V
VCON = 1.2V
320 450
310 450
85 120
700 820
940
800 1000 1200
1.8 2 2.2
3
10
mΩ
mΩ
mΩ
mA
mA
MHz
V/V
nA
Buck System Characteristics (Note 2) The following spec table entries are guaranteed by design if the
component values in the typical application circuit are used. These parameters are not guaranteed by production testing.
Symbol
TRESPONSE
TSTARTUP
CCON
TON_BYP
TBYP
Parameter
Conditions
Time for VOUT to Rise from
0.8V to 3.4V in PWM Mode
Time for VOUT to rise to 3.4V
in PWM Mode
(Note 14)
VIN = 4.2V, COUT = 4.7µF,
RLOAD = 15Ω
L = 2.2 µH (ISAT > 0.94A)
VIN = 4.2V, COUT = 4.7µF,
RLOAD = 15Ω
L = 2.2µH (ISAT = 0.94A)
EN = Low to High
VCON Input Capacitance
VIN = 3.6V, VCON = 1V,
Test Freq. = 100kHz
Bypass FET Turn On Time In VIN = 3.6V, VCON = 0.267V,
Bypass Mode
COUT = 4.7µF, RLOAD = 15Ω
BYP = Low to High
Auto Bypass Detect Delay (Note 10)
Time
Min Typ Max
25
Units
µs
36
15
30
10 15 20
µs
pF
µs
µs
5 www.national.com
5 Page 
Line Transient Response
(VIN = 3.0V to 3.6V)
Load Transient Response
(VCON = 0.5V)
20181930
VCON Voltage Response
(VIN = 4.2V, VCON = 0.5V / 1.1V)
20181924
Timed Current Limit Response
(Normal Operation to Short Circuit)
20181931
Output Voltage Ripple
(VOUT = 1.5V)
20181932
Output Voltage Ripple in Dropout
(VIN = 3.75V, VOUT = 3.25V, IOUT = 200mA)
20181933
11
20181934
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11 Page | ||
| Páginas | Total 22 Páginas | |
| PDF Descargar | [ Datasheet LM3280.PDF ] | |
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