LM2612
400mA Sub-miniature, Programmable, Step-Down DC-DC
Converter for Ultra Low-Voltage Circuits
General Description
The LM2612 step-down DC-DC converter is optimized for
powering ultra-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 out-
put voltages of 1.05V, 1.3V, 1.5V or 1.8V allow adjustment
for MPU voltage options without board redesign or external
feedback resistors.
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. In PWM mode, in-
ternal synchronous rectification provides high efficiency
(91% typ. at 1.8V
OUT
). A SYNC input allows synchronizing
the switching frequency in a range of 500kHz to 1MHz to
avoid noise from intermodulation with system frequencies.
Low-current hysteretic PFM mode reduces quiescent current
to 150 A (typ.) during system standby. Shutdown mode
turns the device off and reduces battery consumption to
0.1A (typ.). Additional features include soft start and current
overload protection.
The LM2612 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
Pin programmable output voltage (1.05V, 1.3V, 1.5V and
1.8V)
n
400mA maximum load capability (300mA for B grade)
n
2% PWM mode DC output voltage precision
n
2mV typ PWM mode output voltage ripple
n
150 A typ PFM mode quiescent current
n
0.1A typ shutdown mode current
n
Internal synchronous rectification for high PWM mode
efficiency (91% at 2.8V
IN
, 1.8V
OUT
)
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
No external compensation required
Applications
n
Mobile Phones
n
Hand-Held Radios
n
Battery Powered Devices
Typical Application Circuit
20007102
May 2002
LM2612
400mA
Sub-miniature,
Programmable,
Step-Down
DC-DC
Converter
for
Ultra
Low-V
oltage
Circuits
2002 National Semiconductor Corporation
DS200071
www.national.com
Connection Diagrams
micro SMD package
20007104
TOP VIEW
20007105
BOTTOM VIEW
Ordering Information
Order Number
Package Type
NSC Package
Drawing
Supplied As
10-Pin micro SMD
LM2612ABP
10-bump Wafer Level Chip Scale
(micro SMD)
BPA10VWB
250 Units, Tape and Reel
LM2612BBP
250 Units, Tape and Reel
LM2612ABPX
3000 Units, Tape and Reel
LM2612BBPX
3000 Units, Tape and Reel
Pin Description
Pin Number(*)
Pin Name
Function
A1
FB
Feedback Analog Input. Connect to the output at the output filter capacitor (Figure 1)
B1
VID1
Output Voltage Control Inputs. Set the output voltage using these digital inputs (see Table
1). The output defaults to 1.5V if these pins are unconnected.
C1
VID0
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 to an external clock in
PWM mode. See
Synchronization and Operating Modes in the Device Information section.
D2
EN
Enable Input. Set this CMOS Schmitt trigger digital input high to VDD for normal
operation. For shutdown, set low to SGND. Set EN low during 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 850mA max
Switch Peak Current Limit specification of the LM2612 (
Figure 1)
B3
PVIN
Power Supply Input to the internal PFET switch. Connect to the input filter capacitor
(
Figure 1).
A3
VDD
Analog Supply Input. If board layout is not optimum, an optional 0.1F ceramic capacitor
is suggested (
Figure 1)
A2
SGND
Analog and Control Ground
(*) note the pin numbering scheme for the MicroSMD package was revised in April, 2002 to comform to JEDEC standard. Only the pin numbers were revised. No
changes to the physical location of the inputs/outputs were made. For reference purpose, the obsolete numbering has FB as pin 1, VID1 as pin 2, VID0 as pin 3,
SYNC as pin 4, EN as pin 5, PGND as pin 6, SW as pin 7, PVIN as pin 8, VDD as pin 9 and SGND as pin 10.
LM2612
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2
Absolute Maximum Ratings
(Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
PVIN, VDD, to SGND
-0.2V to +6V
PGND to SGND
-0.2V to +0.2V
EN, SYNC/MODE, VID0, VID1 to
SGND
-0.2V to +6V
FB, SW
(GND -0.2V) to
(VDD +0.2V)
Storage Temperature Range
-45C to +150C
Lead temperature
(Soldering, 10 sec.)
260C
Junction Temperature (Note 2)
-25C to 125C
Minimum ESD Rating
Human body model, C = 100pF, R =
1.5 k
2.5kV
Thermal Resistance (
JA
)
LM2612ABP & LM2612BBP (Note 3)
170C/W
Electrical Characteristics
Specifications with standard typeface are for T
A
= T
J
= 25C, and those in bold face type apply over the full Operating Tem-
perature Range (T
A
= T
J
= -25C to +85C). Unless otherwise specified, PVIN = VDD = EN = SYNC = 3.6V, VID0 = VID1 =
0V.
Symbol
Parameter
Conditions
Min
Typ
Max
Units
V
IN
Input Voltage Range (Note
5)
PVIN = VDD = VID1 = V
IN
,
VID0 = 0V
2.8
5.5
V
V
FB
Feedback Voltage
(Note 6)
VID0 = V
IN
, VID1 = V
IN
1.00
1.05
1.10
V
VID0 = V
IN
, VID1 = 0V
1.274
1.30
1.326
VID0 = 0V, VID1 = 0V
1.470
1.50
1.530
VID0 = 0V, VID1 = V
IN
1.764
1.8
1.836
V
HYST
PFM Comparator Hysteresis
Voltage
(Note 7)
PFM Mode (SYNC = 0V)
16
mV
I
SHDN
Shutdown Supply Current
EN = 0V
0.1
3
A
I
Q1
DC Bias Current into VDD
(V
OUT
set to 1.5V)
No-Load, PFM mode
(SYNC/MODE = 0V)
150
185
A
I
Q2
No-Load, PWM mode
(SYNC/MODE = V
IN
)
555
725
R
DSON (P)
Pin-Pin Resistance for P
FET
LM2612ABP & LM2612BBP
370
500
m
R
DSON (N)
Pin-Pin Resistance for N
FET
LM2612ABP & LM2612BBP
330
500
m
R
DSON , TC
FET Resistance
Temperature Coefficient
0.5
%/C
I
lim
Switch Peak Current Limit
(Note 8)
LM2612ABP
510
690
850
mA
LM2612BBP
400
690
980
V
EN_H
EN Positive Going
Threshold Voltage
(Note 8)
V
DD
= 3.6V
2.54
2.85
V
V
EN_L
EN Negative Going
Threshold Voltage
(Note 8)
V
DD
= 3.6V
1.70
2.00
V
V
SYNC_H
SYNC/MODE Positive
Going Threshold Voltage
0.95
1.3
V
V
SYNC_L
SYNC/MODE Negative
Going Threshold Voltage
0.4
0.9
V
V
ID_H
V
ID0
, V
ID1
Positive Going
Threshold Voltage
0.92
1.2
V
V
ID_L
V
ID0
, V
ID1
Negative Going
Threshold Voltage
0.4
0.83
V
LM2612
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Electrical Characteristics
(Continued)
Specifications with standard typeface are for T
A
= T
J
= 25C, and those in bold face type apply over the full Operating Tem-
perature Range (T
A
= T
J
= -25C to +85C). Unless otherwise specified, PVIN = VDD = EN = SYNC = 3.6V, VID0 = VID1 =
0V.
Symbol
Parameter
Conditions
Min
Typ
Max
Units
I
VID
VID1, VID0 Pull Down
Current
VID1, VID0 = 3.6V
1.8
A
f
sync
SYNC/MODE Clock
Frequency Range
(Note 10)
500
1000
kHz
F
OSC
Internal Oscillator
Frequency
LM2612ABP, PWM Mode
(SYNC = VIN)
468
600
732
kHz
LM2612BBP, PWM Mode
(SYNC = VIN)
450
600
750
T
min
Minimum ON-Time of P FET
Switch in PWM Mode
200
ns
Load Transient Response in
PWM Mode
Circuit of
Figure 1
I
OUT
= 20mA to 200mA Step
25
mV
Line Transient Response in
PFM Mode
Circuit of
Figure 1
V
IN
= 3.0V to 3.6V Step
t
r
= t
p
= 10 s
3
mV
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 25C and are not guaranteed.
Note 2: In PWM mode, Thermal shutdown will occur if the junction temperature exceeds the 150C maximum junction temperature of the device.
Note 3: Thermal resistance specified with 2 layer PCB(0.5/0.5 oz. cu).
Note 4: Thermal resistance specified with 3 layer PCB (2/1/1 oz. cu) and 12 vias 0.33mm diameter (see Application Note AN-1187).
Note 5: The LM2612 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 LM2612 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 LM2612 exhibited safe behavior during pre-production evaluation while enabled at low input voltages, this is not guaranteed.
Note 6: The feedback voltage is trimmed at the 1.5V 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%, except for the 1.05V setting, which is 5%. Contact the Portable Power Applications group at National Semiconductor,
if trimming at other voltages is desired.
Note 7: : 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 8: 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 s to allow the inductor current to diminish.
Note 9: EN is a CMOS Schmitt trigger digital input with logic thresholds that scale with the supply voltage at the VDD pin. The nominal logic thresholds are
approximately 0.71VDD and 0.55VDD for the high and low thresholds respectively.
Note 10: SYNC driven with an external clock switching between V
IN
and GND. When an external clock is present at SYNC, the IC is forced to PWM mode at the
external clock frequency. The LM2612 synchronizes to the rising edge of the external clock.
LM2612
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4
Typical Operating Characteristics
LM2612ABP, Circuit of
Figure 1, V
IN
= 3.6V, T
A
= 25C,
L
1
= 10 H, unless otherwise noted.
Quiescent Supply Current vs Temperature
Quiescent Supply Current vs Supply Voltage
20007106
20007107
Shutdown Quiescent Current vs Temperature
Output Voltage vs Temperature (PWM Mode)
20007108
20007109
Output Voltage vs Temperature (PFM Mode)
Output Voltage vs Supply Voltage
(V
OUT
= 1.8V, PWM Mode)
20007110
20007111
LM2612
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