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LM2614
400mA Sub-Miniature Adjustable DC-DC Converter
Optimized for RF Power Amplifiers
LM2614 400mA Sub-Miniature Adjustable DC-DC Converter Optimized for RF Power Amplifiers
August 2002
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 reduces battery consumption to 0.02µA (typ.).
Current limit and thermal shutdown features protect the device 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 technology and offers the smallest possible size. Ahigh switching
frequency (600kHz) allows use of tiny surface-mount components.
The LM2614 can be dynamically controlled for output voltage changes from 1.0V to 3.6V in
tures external compensation to tailor the response to a wide
range of operating conditions.
<
30µs. The device fea-
Key Specifications
n Operates from a single LiION cell (2.8V to 5.5V)
n Adjustable output voltage (1.0V to 3.6V)
±
n
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
in PWM mode from internal synchronous rectification
n 100% Maximum Duty Cycle for Lowest Dropout
, 3.6V
IN
and 200mA)
OUT
Features
n Sub-miniature 10-bump thin micro SMD package
n Uses small ceramic capacitors
n 5mV typ PWM mode output voltage ripple(C
n Internal soft start
n Current overload protection
n Thermal Shutdown
n External compensation
OUT
= 22µF)
Applications
n Mobile Phones
n Hand-Held Radios
n RF PC Cards
n Battery Powered RF Devices
© 2002 National Semiconductor Corporation DS200367 www.national.com
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Connection Diagrams
10-Bump micro SMD Package
LM2614
Top View
20036704
Bottom View
20036705
Ordering Information
Order Number Package Type
LM2614ATL
LM2614BTL XYTT S50B 250 Tape and Reel
LM2614ATLX XYTT S50A 3000 Tape and Reel
LM2614BTLX XYTT S50B 3000 Tape and Reel
(*) XY - denotes the date code marking (2 digit) in production
(*) TT - refers to die run/lot traceability for production
(*) S - product line designator
Package markings may change over the course of production.
10-bump Wafer Level Chip Scale
(micro SMD)
NSC Package
*
Marking (
XYTT S50A 250 Tape and Reel
)
Supplied As
Pin Description
Pin Number Pin Name Function
A1 FB Feedback Analog Input.
B1 EANEG Inverting input of error amplifier
C1 EAOUT Output of error amplifier
D1 SYNC/MODE Synchronization Input. Use this digital input for frequency selection or modulation control.
Set:
SYNC/MODE = high for low-noise 600kHz PWM mode
SYNC/MODE = low for low-current PFM mode
SYNC/MODE = a 500kHz–1MHz external clock for synchronization in PWM mode. (See
Synchronization and Operating Modes in the Device Information section.)
D2 EN Enable Input. Set this Schmitt trigger digital input high for normal operation. For shutdown,
set low. Set EN low during system power-up and other low supply voltage conditions.
(See Shutdown Mode in the Device Information section.)
D3 PGND Power Ground
C3 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 of the LM2614.
B3 PVIN Power Supply Voltage Input to the internal PFET switch. Connect to the input filter
capacitor.
A3 VDD Analog Supply Input. If board layout is not optimum, an optional 0.1µF ceramic capacitor
is suggested.
A2 SGND Analog and Control Ground
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Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
LM2614
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
PVIN, VDD to SGND −0.2V to +6V
PGND to SGND, PVIN to VDD −0.2V to +0.2V
EN, EAOUT, EANEG, SYNC/MODE
Storage Temperature Range −45˚C to +150˚C
Lead Temperature
(Soldering, 10 sec.) 260˚C
Junction Temperature (Note 2) −25˚C to +125˚C
Minimum ESD Rating
(Human Body Model, C = 100 pF, R = 1.5 kΩ)
Thermal Resistance (θ
) (Note 3) 140˚C/W
JA
to SGND −0.2V to +6V
FB, SW (GND −0.2V) to
(VDD +0.2V)
Electrical Characteristics
Specifications with standard typeface are for TA=TJ= 25˚C, and those in boldface type apply over the full Operating Temperature Range of T
Symbol Parameter Conditions Min Typ Max Units
V
V
V
IN
FB
HYST
Input Voltage Range PVIN = VDD = VIN(Note 4) 2.8 3.6 5.5 V
Feedback Voltage 1.485 1.50 1.515 V
PFM Comparator Hysteresis
Voltage
I
SHDN
I
Q1_PWM
I
Q2_PFM
R
DSON (P)
Shutdown Supply Current VIN = 3.6V, EN = 0V 0.02 3 µA
DC Bias Current into VDD SYNC/MODE = VIN
Pin-Pin Resistance for
P FET
R
DSON (N)
Pin-Pin Resistance for
N FET
R
DSON (TC)
FET Resistance
Temperature Coefficient
I
LIM
Switch Peak Current Limit
(Note 6)
V
IH
Logic High Input, EN,
SYNC/MODE
V
IL
Logic Low Input, EN,
SYNC/MODE
F
SYNC
SYNC/MODE Clock
Frequency Range
F
OSC
Internal Oscillator
Frequency
T
min
Minimum ON-Time of PFET
Switch in PWM Mode
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is
functional, but device 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. Typical (typ) specifications are mean or average values at 25˚C and are not guaranteed.
Note 2: Thermal shutdown will occur if the junction temperature exceeds 150˚C.
Note 3: Thermal resistance specified with 2 layer PCB (0.5/0.5 oz. cu).
Note 4: The LM2614 is designed for mobile phone applications where turn-on after system power-up is controlled by the system controller. Thus, it should be kept
in shutdown by holding the EN pin low until the input voltage exceeds 2.8V.
Note 5: The hysteresis voltage is the minimum voltage swing on the FB pin that causes the internal feedback and control circuitry to turn the internal PFET switch
on and then off during PFM mode. When resistor dividers are used like in the operating circuit of Figure 4, the hysteresis at the output will be the value of the
hysteresis at the feedback pin times the resistor divider ratio. In this case, 24mV (typ) x ((46.4k + 33.2k)/33.2k).
Note 6: Current limit is built-in, fixed, and not adjustable. If the current limit is reached while the voltage at the FB pin is pulled below 0.7V, the internal PFET switch
turns off for 2.5µs to allow the inductor current to diminish.
Note 7: SYNC driven with an external clock switching between V
the external clock frequency. The LM2614 synchronizes to the rising edge of the external clock.
= −25˚C to +85˚C. Unless otherwise specified, PVIN = VDD = EN = SYNC/MODE = 3.6V.
A=TJ
PFM Mode (SYNC/MODE =
0V) (Note 5)
FB=2V
SYNC/MODE = 0V
FB=2V
24 mV
600 725 µA
160 195 µA
395 550 mΩ
330 500 mΩ
0.5 %/C
LM2614ATL 510 690 850
LM2614BTL 400 690 980
0.95 1.3 V
0.4 0.80 V
(Note 7)
500 1000 kHz
LM2614ATL, PWM Mode 468 600 732
LM2614BTL, PWM Mode 450 600 750
200 ns
and GND. When an external clock is present at SYNC; the IC is forced to be in PWM mode at
IN
±
2kV
mA
kHz
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Typical Performance Characteristics
LM2614ATL, Circuit of Figure 4,VIN= 3.6V, TA= 25˚C, unless otherwise noted.
Shutdown Quiescent Current vs Temperature
Quiescent Supply Current vs Supply Voltage
LM2614
(Circuit in Figure 3)
Output Voltage vs Supply Voltage
= 1.0V, PWM MODE)
(V
OUT
Output Voltage vs Output Current
= 1.0V, PWM MODE)
(V
OUT
20036708
20036722
Output Voltage vs Supply Voltage
(V
= 1.5V, PWM MODE)
OUT
20036724 20036709
Output Voltage vs Output Current
(V
= 1.5V, PWM MODE)
OUT
20036710
20036711
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