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LM2612BL
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LM2612BL 400mA Sub-miniature, Programmable, Step-Down DC-DC Converter for Ultra
Low-Voltage Circuits
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FEATURES
APPLICATIONS
•
•
•
•
•
1
2
•
•
•
•
•
Sub-miniature 10-pin DSBGA Package
Only Three Tiny Surface-mount External
Components Required
Uses Small Ceramic Capacitors
Internal Soft Start
Current Overload Protection
No External Compensation Required
Thermal Shutdown Protection
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 output voltages of
1.05V, 1.3V, 1.5V or 1.8V allow adjustment for MPU
voltage options without board redesign or external
feedback resistors.
KEY SPECIFICATIONS
•
•
•
•
•
•
•
•
•
•
Mobile Phones
Hand-Held Radios
Battery Powered Devices
Operates from a Single LiION Cell (2.8V to
5.5V)
Internal Synchronous Rectification for High
PWM Mode Efficiency
Pin Programmable Output Voltage (1.05V,
1.3V, 1.5V and 1.8V)
400mA Maximum Load Capability (300mA for
B Grade)
±2% PWM Mode DC Output Voltage Precision
5mV typ PWM Mode Output Voltage Ripple
160 μA typ PFM Mode Quiescent Current
0.02μA typ Shutdown Mode Current
600kHz PWM Mode Switching Frequency
SYNC Input for PWM Mode Frequency
Synchronization from 500kHz to 1MHz
The device has three pin-selectable modes for
maximizing battery life in mobile phones and similar
portable applications. 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, internal
synchronous rectification provides high efficiency
(91% typ. at 1.8VOUT). 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 160 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.
Typical Application Circuit
VIN
2.8V to 5.5V
VDD
10PF
VOUT Programmable to
1.05V, 1.3V, 1.5V or 1.8V
PVIN
EN
SW
ON/OFF
SYNC/MODE
10PH
LM2612
FB
PWM/PFM
VID0
VID1
SGND
PGND
22PF
1
2
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
All trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2002–2013, Texas Instruments Incorporated
OBSOLETE
LM2612BL
SNVS193D – JUNE 2002 – REVISED APRIL 2013
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DESCRIPTION (CONTINUED)
The LM2612 is available in a 10 pin DSBGA package. This package uses TI's wafer level chip-scale DSBGA
technology and offers the smallest possible size. Only three small external surface-mount components, an
inductor and two ceramic capacitors are required.
Connection Diagrams
DSBGA Package
SGND
SGND
A1
FB
B3
B1
VID1
SW
C3
C1
VID0
PGND
D3
D1
SYNC/
MODE
A3
VDD
VDD
A3
B1
B3
PVIN
PVIN
VID0
C1
C3
SW
SYNC/
MODE
D1
D3
PGND
FB
A1
VID1
A2
D2
A2
D2
EN
EN
Figure 1. TOP VIEW
Figure 2. BOTTOM VIEW
PIN DESCRIPTION
Pin Number (1)
(1)
2
Pin Name
A1
FB
B1
VID1
C1
VID0
D1
SYNC/MODE
D2
EN
D3
PGND
Function
Feedback Analog Input. Connect to the output at the output filter capacitor (Figure 1)
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.
Synchronization Input. Use this digital input for frequency synchronization or modulation control.
Set:
SYNC/MODE = high for low-noise 600kHz PWM mode
SYNC/MODE = low for low-current PFM mode
SYNC/MODE = 500kHz - 1MHz external clock for synchronization to an external clock in PWM
mode. See Frequency Synchronization (SYNC/MODE Pin) and Operating Mode Selection
(SYNC/MODE Pin) in the DEVICE INFORMATION section.
Enable Input. For shutdown, set low to SGND.(See Shutdown Mode in the DEVICE
INFORMATION section.)
Power Ground
C3
SW
B3
PVIN
Switching Node connection to the internal PFET switch and NFET synchronous rectifier.
Power Supply Input to the internal PFET switch. Connect to the input filter capacitor (Figure 29).
A3
VDD
Analog Supply Input. If board layout is not optimum, an optional 0.1µF ceramic capacitor is
suggested (Figure 29)
A2
SGND
Analog and Control Ground
The pin numbering scheme for the DSBGA package was revised in April, 2002 to conform 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 had
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.
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These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
ABSOLUTE MAXIMUM RATINGS (1) (2)
−0.2V to +6V
PVIN, VDD, to SGND
−0.2V to +0.2V
PGND to SGND
−0.2V to +6V
EN, SYNC/MODE, VID0, VID1 to SGND
(GND −0.2V) to (VDD +0.2V)
FB, SW
−45°C to +150°C
Storage Temperature Range
Lead temperature
(Soldering, 10 sec.)
Junction Temperature
260°C
(3)
−25°C to 125°C
Minimum ESD Rating
Human body model, C = 100pF, R = 1.5 kΩ
±2kV
Thermal Resistance (θJA)
LM2612ABL/LM2612ATL & LM2612BBL/LM2612BTL (4)
(1)
140°C/W
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 ensured. For ensured specifications and associated test
conditions, see the Min and Max limits and Conditions in the Electrical Characteristics table. Electrical Characteristics table limits are
specified 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 ensured.
If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office / Distributors for
availability and specifications.
Thermal shutdown will occur if the junction temperature exceeds the 150°C maximum junction temperature of the device.
Thermal resistance specified with 2 layer PCB(0.5/0.5 oz. cu).
(2)
(3)
(4)
ELECTRICAL CHARACTERISTICS
Specifications with standard typeface are for TA = TJ = 25°C, and those in bold face type apply over the full Operating
Temperature Range (TA = TJ = −25°C to +85°C). Unless otherwise specified, PVIN = VDD = EN = SYNC = 3.6V, VID0 =
VID1 = 0V.
Symbol
VIN
Parameter
Input Voltage Range
(1)
Feedback Voltage
VFB
(2)
VHYST
Conditions
PVIN = VDD = VID1 = VIN,
VID0 = 0V
Min
Typ
2.8
Max
Units
5.5
V
VID0 = VIN, VID1 = VIN
1.029
1.05
1.071
VID0 = VIN, VID1 = 0V
1.274
1.30
1.326
VID0 = 0V, VID1 = 0V
1.470
1.50
1.530
VID0 = 0V, VID1 = VIN
1.764
1.8
1.836
PFM Comparator Hysteresis
Voltage
PFM Mode (SYNC = 0V)
ISHDN
Shutdown Supply Current
EN = 0V
0.02
3
IQ1
DC Bias Current into VDD
No switching, PFM mode
(SYNC/MODE = 0V)
160
195
No switching, PWM mode
(SYNC/MODE = VIN)
605
725
25
(3)
IQ2
V
mV
µA
µA
RDSON (P)
Pin-Pin Resistance for P FET
395
550
mΩ
RDSON (N)
Pin-Pin Resistance for N FET
325
500
mΩ
RDSON , TC
FET Resistance Temperature
Coefficient
0.5
(1)
(2)
(3)
%/C
The LM2612 is designed for applications where turn-on after system power-up is controlled by the system processor and internal UVLO
(Under Voltage LockOut) circuitry is unnecessary. 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 exhibits safe behavior while enabled at low input voltages, this is
not ensured.
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%.
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.
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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
Temperature Range (TA = TJ = −25°C to +85°C). Unless otherwise specified, PVIN = VDD = EN = SYNC = 3.6V, VID0 =
VID1 = 0V.
Symbol
Ilim
Parameter
Switch Peak Current Limit
Conditions
(4)
VEN_H
EN Positive Going Threshold
Voltage
VEN_L
EN Negative Going Threshold
Voltage
VSYNC_H
SYNC/MODE Positive Going
Threshold Voltage
VSYNC_L
SYNC/MODE Negative Going
Threshold Voltage
VID_H
VID0, VID1 Positive Going
Threshold Voltage
VID_L
VID0, VID1 Negative Going
Threshold Voltage
IVID
VID1, VID0 Pull Down Current
fsync
SYNC/MODE Clock Frequency
Range
Min
Typ
Max
LM2612ABL/LM2612ATL
510
710
850
LM2612BBL/LM2612BTL
400
710
980
0.95
1.3
0.4
0.95
0.4
0.4
VID1, VID0 = 3.6V
Tmin
(4)
(5)
4
Internal Oscillator Frequency
1.3
500
1.3
V
V
V
3.0
µA
1000
kHz
LM2612ABL/ATL, PWM Mode
(SYNC = VIN)
468
600
732
LM2612BBL/BTL, PWM Mode
(SYNC = VIN)
450
600
750
Minimum ON-Time of P FET
Switch in PWM Mode
V
V
0.83
1.8
mA
V
0.84
0.92
(5)
FOSC
0.80
Units
kHz
200
nS
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.
SYNC driven with an external clock switching between VIN 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.
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TYPICAL OPERATING CHARACTERISTICS
LM2612ABL/ATL, Circuit of Figure 29, VIN = 3.6V, TA = 25°C, L1 = 10 µH, unless otherwise noted.
Quiescent Supply Current vs Temperature
Quiescent Supply Current vs Supply Voltage
Figure 3.
Figure 4.
Shutdown Quiescent Current vs Temperature
Output Voltage vs Temperature (PWM Mode)
Figure 5.
Figure 6.
Output Voltage vs Temperature (PFM Mode)
Output Voltage vs Supply Voltage
(VOUT = 1.5V, PWM Mode)
Figure 7.
Figure 8.
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TYPICAL OPERATING CHARACTERISTICS (continued)
LM2612ABL/ATL, Circuit of Figure 29, VIN = 3.6V, TA = 25°C, L1 = 10 µH, unless otherwise noted.
6
Output Voltage vs Supply Voltage
(VOUT = 1.5V, PFM Mode)
Output Voltage vs Output Current
(VOUT = 1.5V, PWM Mode)
Figure 9.
Figure 10.
Output Voltage vs Output Current
(VOUT = 1.5V, PFM Mode)
Efficiency vs Output Current
(VOUT = 1.8V, PWM Mode, With Diode)
Figure 11.
Figure 12.
Efficiency vs Output Current
(VOUT = 1.8V, PFM Mode, With Diode)
Efficiency vs Output Current
(VOUT = 1.5V, PWM Mode, With Diode)
Figure 13.
Figure 14.
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TYPICAL OPERATING CHARACTERISTICS (continued)
LM2612ABL/ATL, Circuit of Figure 29, VIN = 3.6V, TA = 25°C, L1 = 10 µH, unless otherwise noted.
Efficiency vs Output Current
(VOUT = 1.5V, PFM Mode, With Diode)
Efficiency vs Output Current
(VOUT = 1.3V, PWM Mode, With Diode)
Figure 15.
Figure 16.
Efficiency vs Output Current
(VOUT = 1.3V, PFM Mode, With Diode)
Efficiency vs Output Current
(VOUT = 1.05V, PWM Mode, With Diode)
Figure 17.
Figure 18.
Efficiency vs Output Current
(VOUT = 1.05V, PFM Mode, With Diode)
Efficiency vs Output Current
(VOUT = 1.8V, PWM Mode,No Diode)
Figure 19.
Figure 20.
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TYPICAL OPERATING CHARACTERISTICS (continued)
LM2612ABL/ATL, Circuit of Figure 29, VIN = 3.6V, TA = 25°C, L1 = 10 µH, unless otherwise noted.
Efficiency vs Output Current
(VOUT = 1.8V, PFM Mode, No Diode)
Switching Frequency vs Temperature
(PWM Mode)
Figure 21.
Figure 22.
Load Transient Response (PWM Mode)
Load Transient Response (PFM Mode)
A: INDUCTOR CURRENT, 500mA/div
B: SW PIN, 5V/div
C: VOUT, 50mV/div, AC COUPLED,
D: LOAD, 10mA to 100mA, 100mA/div
Figure 24.
A: INDUCTOR CURRENT, 500mA/div
B: SW PIN, 5V/div
C: VOUT, 50mV/div, AC COUPLED
D: LOAD, 20mA to 200mA, 200mA/div
Figure 23.
Shutdown Response (PWM Mode)
A: INDUCTOR CURRENT, 500mA/div
B: SW PIN, 2V/div
C: VOUT, 1V/div, D: EN, 5V/div
Figure 25.
8
Shutdown Response (PFM Mode)
A: INDUCTOR CURRENT, 500mA/div
B: SW PIN, 2V/div
C: VOUT, 1V/div , D: EN, 5V/div
Figure 26.
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TYPICAL OPERATING CHARACTERISTICS (continued)
LM2612ABL/ATL, Circuit of Figure 29, VIN = 3.6V, TA = 25°C, L1 = 10 µH, unless otherwise noted.
PWM to PFM Response
A: INDUCTOR CURRENT, 500mA/div
B: SW PIN, 2V/div
C: VOUT, 50mV/div, AC COUPLED
D: SYNC/MODE, 5V/div
Figure 27.
Line Transient Response (PWM Mode)
A: SUPPLY VOLTAGE, 500mV/div, AC COUPLED
B: SW PIN, 5V/div
C: VOUT, 10mV/div, AC COUPLED
L1 = 22 µH
Figure 28.
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DEVICE INFORMATION
The LM2612 is a simple, step-down DC-DC converter optimized for powering low-voltage CPUs or DSPs in cell
phones and other miniature battery powered devices. It provides pin-selectable output voltages of 1.05V, 1.3V,
1.5V or 1.8V from a single 2.8V to 5.5V LiION battery cell. It is designed for a maximum load current of 400mA
(300mA for B grade).
The device has all three of the pin-selectable operating modes required for cell phones and other complex
portable devices. Such applications typically spend a small portion of their time operating at full power. During full
power operation, synchronized or fixed-frequency PWM mode offers full output current capability while
minimizing interference to sensitive IF and data acquisition circuits. PWM mode uses synchronous rectification
for high efficiency: typically 91% for a 100mA load with 1.8V output, 2.8V input. These applications spend the
remainder of their time in low-current standby operation or shutdown to conserve battery power. During standby
operation, hysteretic PFM mode reduces quiescent current to 160µA typ to maximize battery life. Shutdown
mode turns the device off and reduces battery consumption to 0.02µA (typ.).
The LM2612 offers good performance and a full set of features. It is based on a current-mode switching buck
architecture. The SYNC/MODE input accepts an external clock between 500kHz and 1MHz. The output voltage
selection pins eliminate external feedback resistors. Additional features include soft-start, current overload
protection, over-voltage protection and thermal shutdown protection.
The LM2612 is constructed using a chip-scale 10-pin DSBGA package. The DSBGA package offers the smallest
possible size for space critical applications, such as cell phones. Required external components are only a small
10uH inductor, and tiny 10uF and 22uF ceramic capacitors for reduced board area.
C3*
0.1PF
C1
VIN
2.8V to 5.5V
10PF
VDD
PVN
L1 = 10PH
VOUT 1.5V
SW
D1*
LM2612
SYSTEM PROCESSOR
FB
PWM/PFM
ON/OFF
SYNC/MODE
VID1
EN
VID0
SGND
C2
22PF
*C3 IS OPTIONAL
*D1 IS OPTIONAL
PGND
Figure 29. Typical Operating Circuit
Circuit Operation
Referring to Figure 29, Figure 30, and Figure 31, the LM2612 operates as follows: During the first part of each
switching cycle, the control block in the LM2612 turns on the internal PFET switch. This allows current to flow
from the input through the inductor to the output filter capacitor and load. The inductor limits the current to a
ramp with a slope of (VIN -VOUT)/L, by storing energy in a magnetic field. During the second part of each cycle,
the controller turns the PFET switch off, blocking current flow from the input, and then turns the NFET
synchronous rectifier on. In response, the inductor's magnetic field collapses, generating a voltage that forces
current from ground through the synchronous rectifier to the output filter capacitor and load. As the stored energy
is transferred back into the circuit and depleted, the inductor current ramps down with a slope of VOUT/L. If the
inductor current reaches zero before the next cycle, the synchronous rectifier is turned off to prevent current
reversal. The output filter capacitor stores charge when the inductor current is high, and releases it when low,
smoothing the voltage across the load.
10
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The output voltage is regulated by modulating the PFET switch on-time to control the average current sent to the
load. The effect is identical to sending a duty-cycle modulated rectangular wave formed by the switch and
synchronous rectifier to a low-pass filter created by the inductor and output filter capacitor. The output voltage is
equal to the average voltage at the SW pin.
VDD
SYNC/
MODE
OSCILLATOR AND
MODE CONTROL
PVIN
¦
CURRENT
SENSE
ERROR AMPLIFIER
FB
PWM COMP
OVP
COMPARATOR
VID0
DAC
VID1
MOSFET
CONTROL
LOGIC
PFM
COMPARATOR
REF
SW
ZERO CROSSING
DETECTOR
SHUTDOWN
CONTROL
SOFT START
EN
PGND
SGND
Figure 30. Simplified Functional Diagram
PWM Operation
The LM2612 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 regulated by switching at a constant frequency and
then modulating the energy per cycle to control power to the load. Energy per cycle is set by modulating the
PFET switch on-time pulse-width to control the peak inductor current. This is done by controlling the PFET switch
using a flip-flop driven by an oscillator and a comparator that compares a ramp from the current-sense amplifier
with an error signal from a voltage-feedback error amplifier. At the beginning of each cycle, the oscillator sets the
flip-flop and turns on the PFET switch, causing the inductor current to ramp up. When the current sense signal
ramps past the error amplifier signal, the PWM comparator resets the flip-flop and turns off the PFET switch,
ending the first part of the cycle. The NFET synchronous rectifier turns on until the next clock pulse or the
inductor current ramps to zero. If an increase in load pulls the output voltage down, the error amplifier output
increases, which allows the inductor current to ramp higher before the comparator turns off the PFET switch.
This increases the average current sent to the output and adjusts for the increase in the load.
Before going to the PWM comparator, the current sense signal is summed with a slope compensation ramp from
the oscillator for stability of the current feedback loop. During the second part of the cycle, a zero crossing
detector turns off the NFET synchronous rectifier if the inductor current ramps to zero.
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PWM Mode Switching Waveform
A: INDUCTOR CURRENT, 500mA/div
B: SW PIN, 2V/div
C: VOUT, 10mV/div, AC COUPLED
PFM Mode Switching Waveform
A: INDUCTOR CURRENT, 500mA/div
B: SW PIN, 2V/div
C: VOUT, 50mV/div, AC COUPLED
Figure 31. Typical Circuit Waveforms in (a) PWM Mode and (b) PFM Mode
PFM Operation
Connecting the SYNC/MODE pin to SGND sets the LM2612 to hysteretic PFM operation. While in PFM (Pulse
Frequency Modulation) mode, the output voltage is regulated by switching with a discrete energy per cycle and
then modulating the cycle rate, or frequency, to control power to the load. This is done by using an error
comparator to sense the output voltage and control the PFET switch. The device waits as the load discharges
the output filter capacitor, until the output voltage drops below the lower threshold of the PFM error-comparator.
Then the error comparator initiates a cycle by turning on the PFET switch. This allows current to flow from the
input, through the inductor to the output, charging the output filter capacitor. The PFET switch is turned off when
the output voltage rises above the regulation threshold of the PFM error comparator. After the PFET switch turns
off, the output voltage rises a little higher as the inductor transfers stored energy to the output capacitor by
pushing current into the output capacitor. Thus, the output voltage ripple in PFM mode is proportional to the
hysteresis of the error comparator and the inductor current.
In PFM mode, the device only switches as needed to service the load. This lowers current consumption by
reducing power consumed during the switching action in the circuit due to transition losses in the internal
MOSFETs, gate drive currents, eddy current losses in the inductor, etc. It also improves light-load voltage
regulation. During the second part of the cycle, the intrinsic body diode of the NFET synchronous rectifier
conducts until the inductor current ramps to zero. The LM2612 does not turn on the synchronous rectifier while in
PFM mode.
Operating Mode Selection (SYNC/MODE Pin)
The SYNC/MODE digital input pin is used to select between PWM or PFM operating modes. Set SYNC/MODE
high (above 1.3V) for 600kHz PWM operation when the system is active and the load is above 50mA. Set
SYNC/MODE low (below 0.4V) to select PFM mode when the load is less than 50mA for precise regulation and
reduced current consumption when the system is in standby. The LM2612 has an over-voltage protection feature
that may activate if the device is left in PWM mode under low-load conditions (