LMR22007
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SNVS985A – OCTOBER 2013 – REVISED OCTOBER 2013
LMR22007 2.7V - 20V, 750mA Step-Down Converter with Adjustable Input Current Limit
Check for Samples: LMR22007
FEATURES
APPLICATIONS
•
•
•
1
2
•
•
•
•
•
•
•
•
•
•
•
•
•
High efficiency
– Greater than 90% at 12 VIN to 5 VOUT
Adjustable input current limit from 150mA to
600mA
Input voltage range: 2.7V to 20V
Adjustable output voltage from 0.9V to 5.5V
Up to 750 mA output current
Ultra low quiescent current (18µA typical)
Ultra low shutdown current (300nA typical)
< +/-2% VOUT ripple at no load
< +/-1% VOUT ripple at full load
Internal compensation, Soft-start and Thermal
Shutdown
Solution size less than 26mm2
– Low BOM count with small external
components
Wafer Chip Scale Package (WCSP)
Light load power save mode
Set frequency of 2.1 MHz (typical)
•
•
•
3.3V, 5V and 12V Interface
POL Supply from Single or Multiple Li-Ion
Battery
Solid-State Disk Drives
LDO Replacement
Mobile PC’s, Tablet, Modems, Cameras
DESCRIPTION
The LMR22007 is a switching regulator designed for
the high-efficiency requirement of applications with
stand-by and shut-down modes. The device features
a low-current mode to maintain efficiency under lightload conditions, and an adaptive on-time control
architecture for fast transient response.
The LMR22007 can deliver up to 750mA of
continuous load current with an adjustable input
current limit. The device has a wide input voltage
range of 2.7V to 20V, and supports VIN transients to
24V. Other features include internal compensation,
internal soft start, input under-voltage protection,
internal bootstrap diode, and thermal shutdown.
TYPICAL APPLICATION
Cin
10µF
Cout
22µF
Vin
4.5 ± 20V
Rlim
200k
Vout
3.3V
EN
VIN
PGND
ILIM
PG
SW
AGND
FB
VOUTS
Rfbb
100k
*
L
2.2µH
Rfbt
267k
*
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.
DCS-Control is a trademark of Texas Instruments.
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 © 2013, Texas Instruments Incorporated
LMR22007
SNVS985A – OCTOBER 2013 – REVISED OCTOBER 2013
ABSOLUTE MAXIMUM RATINGS
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(1)
Over operating free-air temperature range (unless otherwise noted)
Pin voltage range
(2)
MIN
MAX
UNIT
VIN, SW, PG
-0.3
24
V
EN
-0.3
24
VOUT
-0.3
6
FB, ILIM
-0.3
3.3
Power good sink current
PG
10
mA
Temperature range
Operating junction
temperature range, TJ
-40
125
°C
Storage temperature
range, Tstg
-65
150
ESD rating
(1)
(2)
(1)
HBM Human body model
2
CDM Charge device
model
0.5
kV
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, and functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating
Conditions is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
The input negative-voltage and output voltage ratings may be exceeded if the input and output current ratings are observed. All voltages
are with respect to network ground terminal.
RECOMMENDED OPERATING CONDITIONS
Over operating free-air temperature range (unless otherwise noted)
Pin voltage range
MIN
MAX
UNIT
VIN, EN, PG
2.7
20
V
VOUT
0.9
5.5
Power Good sink current
PG
Temperature range
Operating junction
temperature range, TJ
-40
100
µA
125
°C
THERMAL CHARACTERISTICS
over operating free-air temperature range (unless otherwise
THERMAL METRIC
(1)
UNIT
θJA
Junction-to-ambient thermal resistance
72.3
°C/W
θJB
Junction-to-board characterization
parameter
32.5
°C/W
(1)
The package thermal impedance is calculated in accordance with JESD 51-7.
ELECTRICAL CHARACTERISTICS
Min and Max Limits apply over the junction temperature (TJ) range of -40°C to +125°C, typical values at VIN = 12V and TA =
25°C (unless otherwise noted)
SYMBOL
PARAMETER
CONDITION
MIN
TYP
MAX
UNIT
IOUT = 0.5A, TJ -40°C to 85°C
0.891
0.9
0.909
V
IOUT = 0.5A, TJ -40°C to 125°C
0.886
0.9
0.914
Regulation and Over-Voltage Comparator
VFB
In-regulation feedback voltage
IFB
Feedback input bias current
0.25
nA
Quiescent Current
IQ
Non Switching Quiescent Current
Non Switching
18
100
µA
ISD
Shut down
VEN = 0V, TJ = -40°C to 85°C
0.3
2
μA
VIN Rising threshold
2.3
2.6
V
VIN Under Voltage Lockout (UVLO)
VUVLO
VIN Under Voltage Lockout
VUVLO-HYS
VIN UVLO Hysteresis
2
269
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ELECTRICAL CHARACTERISTICS (continued)
Min and Max Limits apply over the junction temperature (TJ) range of -40°C to +125°C, typical values at VIN = 12V and TA =
25°C (unless otherwise noted)
SYMBOL
PARAMETER
CONDITION
MIN
TYP
MAX
UNIT
Internal soft-start time
VOUT 10% to 90%, TJ -40°C to 85°C
1.4
3.3
5
ms
RPG
Power Good Pull-Down
Resistance
IOUT = 5mA, EN = 2V
70
Ohms
VPG_Rising
Power Good Pin is floating when
VFB rises above this voltage
0.855
V
VPG_Falling
Power Good Pin is pulled low
when VFB falls below this voltage
0.812
V
2.09
MHz
77
ns
Softstart
SS
Power Good
Switch Frequency Range
fSW
Ton
Minimum on time of NMOS highside Switch
Toff
Minimum off time of NMOS lowside Switch
TJ = 25°C
D-max
The Max Duty Cycle of the high
side NMOS FET
IOUT = 750mA
157
80
ns
%
Switch Characteristics
RDSON-NMOS-HIGH
High Side NMOS switch onresistance
0.141
0.21
Ω
RDSON-NMOS-LOW
Low side NMOS switch onresistance
0.1
0.144
Ω
1000
1150
mA
Input Current limit
ILIMIN
Open Loop Input current limit
RLIM = 15kΩ, VIN = 12V, TJ = 25°C
ILIMIN_HOT
Open Loop Input current limit
RLIM = 15kΩ, VIN = 12V, TJ =
125°C
925
907
ILIMIN_COLD
Open Loop Input current limit
RLIM = 15kΩ, VIN = 12V, TJ = -40°C
1084
Current limit for NMOS switch devices
ILIMIT-
LOWSIDE
ILIMITLOWSIDE_HOT
ILIMITLOWSIDE_COLD
Current limit for short circuit and
faults
TJ = 25°C
900
977
Current limit for short circuit and
faults
TJ = 125°C
858
Current limit for short circuit and
faults
TJ = -40°C
1008
Enable threshold-Rising
VEN Rising
Enable threshold-Falling
VEN Falling
mA
Enable Control
VEN
0.662
0.4
0.9
0.612
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V
3
LMR22007
SNVS985A – OCTOBER 2013 – REVISED OCTOBER 2013
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9 Bump WCSP Package, Bump size 300 µm, 0.5mm pitch
Top View and Bottom View
C3
C2
C1
B3
B2
B1
A3
A2
A1
C1
C2
C3
B1
B2
B3
A1
A2
A3
PIN FUNCTIONS
NO.
NAME
TYPE(1)
DESCRIPTION
A1
AGND
G
Ground reference for all internal circuitry.
A2
ILIM
I
Connect to ground through a resistor to adjust input current limit, see applications information. DO NOT
FLOAT.
A3
EN
I
The device is in shutdown mode when voltage to the EN pin is 0.9V. Do not
leave this pin floating. Maximum operating voltage on this pin is 20V.
B1
FB
I
Divide down the output voltage with a resistor divider to 0.9 and connect to this pin.
B2
PG
O
Power good flag. Open drain connection of an internal pull-down MOSFET. Tie a resistor from the desired
logic voltage to the PG pin. The pin will float when the FB pin is greater than 0.855V. The pin will be
pulled down when VIN > 2.5V and the FB pin is less than 0.812V.
B3
VIN
P
Input voltage to the device. Connect directly to closely placed input bypass capacitor.
C1
VOUT
I
Connect to the regulated output voltage.
C2
SW
O
Connection to the external inductor.
C3
PGND
G
Power ground connection to internal half bridge. Connect directly to closely placed input bypass
capacitor.
TYPICAL CHARACTERISTICS
Input Current Limit vs VIN
VOUT = 1.2V
100K
50K
75K
Iout = 750mA
Input Current Limit (A)
0.5
0.4
0.3
0.2
0.1
0.6
100K
50K
75K
Iout = 750mA
0.5
Input Current Limit (A)
0.6
Input Current Limit vs VIN
VOUT = 2.5V
0.4
0.3
0.2
0.1
0.0
0.0
2.7
3.3
3.9
4.5
5.1
Vin (V)
5.7
6.3
6.9
4
C001
Figure 1.
4
5
6
7
Vin (V)
8
9
10
C002
Figure 2.
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TYPICAL CHARACTERISTICS (continued)
Input Current Limit vs VIN
VOUT = 3.3V
0.6
0.7
100K
50K
75K
Iout = 750mA
100K
50K
75K
Iout = 750mA
0.6
Input Current Limit (A)
0.5
Input Current Limit (A)
Input Current Limit vs VIN
VOUT = 5V
0.4
0.3
0.2
0.1
0.5
0.4
0.3
0.2
0.1
0.0
0.0
5
6
7
8
9
10
11
Vin (V)
7
12
8
9
10
C003
Power Dissipation 5V
0.7
0.6
14
C004
5.050
0.4
5.025
9Vin @ ±40C
9Vin @ 25C
9Vin @ 85C
12Vin @ ±40C
12Vin @ 25C
12Vin @ 85C
15Vin @ ±40C
15Vin @ 25C
15Vin @ 85C
20Vin @ ±40C
20Vin @ 25C
20Vin @ 85C
5.000
0.3
4.975
0.2
0.1
4.950
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Load (A)
0.0
0.8
0.1
0.2
0.3
0.5
0.6
0.7
0.8
C002
Figure 6.
Efficiency 5V @85°C
Efficiency 5V @25°C
100
100
90
90
80
80
70
70
Efficiency (%)
Efficiency (%)
0.4
Load (A)
C001
Figure 5.
60
50
40
30
60
50
40
30
9Vin
12Vin
15Vin
20Vin
20
10
0
0.001
16
VOUT Regulation 5V
0.5
0.0
15
5.075
Vout (V)
Power Dissipation (W)
0.8
13
Figure 4.
9Vin @ 25C
9Vin @ 85C
12Vin @ 25C
12Vin @ 85C
15Vin @ 25C
15Vin @ 85C
20Vin @ 25C
20Vin @ 85C
0.9
12
Vin (V)
Figure 3.
1.0
11
0.01
0.1
Load (A)
9Vin
12Vin
15Vin
20Vin
20
10
1
0
0.001
C004
Figure 7.
0.01
0.1
Load (A)
1
C005
Figure 8.
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SNVS985A – OCTOBER 2013 – REVISED OCTOBER 2013
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TYPICAL CHARACTERISTICS (continued)
Efficiency 5V @-40°C
Power Dissipation 3.3V
1.0
90
0.9
80
0.8
Power Dissipation (W)
100
Efficiency (%)
70
60
50
40
30
9Vin
12Vin
15Vin
20Vin
20
10
0
0.001
0.01
0.1
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
1
Load (A)
5Vin @ 25C
5Vin @ 85C
9Vin @ 25C
9Vin @ 85C
12Vin @ 25C
12Vin @ 85C
15Vin @ 25C
15Vin @ 85C
20Vin @ 25C
20Vin @ 85C
0.0
90
80
80
70
70
Efficiency (%)
Efficiency (%)
90
60
50
40
30
20
10
0.1
40
0
0.001
90
80
70
Efficiency (%)
Power Dissipation (W)
Efficiency 2.5V @85°C
100
60
50
40
0.2
20
0.1
10
0.0
0.2
0.3
0.4
Load (A)
0.5
0.6
0.7
0.8
0
0.001
C001
Figure 13.
6
1
C008
Figure 12.
30
0.1
0.1
Load (A)
0.3
0.0
0.01
C007
Power Dissipation 2.5V
0.4
5Vin
9Vin
12Vin
15Vin
20Vin
10
3.3Vin @ 25C
3.3Vin @ 85C
5Vin @ 25C
5Vin @ 85C
9Vin @ 25C
9Vin @ 85C
12Vin @ 25C
12Vin @ 85C
15Vin @ 25C
15Vin @ 85C
20Vin @ 25C
20Vin @ 85C
0.5
0.8
50
Figure 11.
0.6
0.7
60
20
1
Load (A)
0.7
0.6
C006
30
5Vin
9Vin
12Vin
15Vin
20Vin
0.8
0.5
Efficiency 3.3V @25°C
100
0.9
0.4
Figure 10.
Efficiency 3.3V @85°C
1.0
0.3
C003
100
0.01
0.2
Load (A)
Figure 9.
0
0.001
0.1
3.3Vin
5Vin
9Vin
12Vin
15Vin
20Vin
0.01
0.1
Load (A)
1
C002
Figure 14.
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TYPICAL CHARACTERISTICS (continued)
Efficiency 2.5V @25°C
Efficiency VOUT = 2.5
90
90
80
80
70
70
Efficiency (%)
100
Efficiency (%)
100
60
50
40
3.3Vin
5Vin
9Vin
12Vin
15Vin
20Vin
30
20
10
0
0.001
0.01
0.1
50
40
3.3Vin
5Vin
9Vin
12Vin
15Vin
20Vin
30
20
10
0
0.001
1
Load (A)
60
0.01
C003
Figure 15.
80
80
70
70
60
60
50
40
3.3Vin
5Vin
9Vin
12Vin
15Vin
20Vin
30
20
10
0.01
0.1
50
40
3.3Vin
5Vin
9Vin
12Vin
15Vin
20Vin
30
20
10
0
0.001
1
Load (A)
0.01
1.2VOUT Regulation
Power Dissipation 1.2V
0.7
3.3Vin @ 25C
3.3Vin @ 85C
5Vin @ 25C
5Vin @ 85C
9Vin @ 25C
9Vin @ 85C
12Vin @ 25C
12Vin @ 85C
15Vin @ 25C
15Vin @ 85C
20Vin @ 25C
20Vin @ 85C
0.6
Power Dissipation (W)
1.206
1.200
Vout
3.3Vin @ ±40C
3.3Vin @ 25C
3.3Vin @ 85C
5Vin @ ±40C
5Vin @ 25C
5Vin @ 85C
9Vin @ ±40C
9Vin @ 25C
9Vin @ 85C
12Vin @ ±40C
12Vin @ 25C
12Vin @ 85C
15Vin @ ±40C
15Vin @ 25C
15Vin @ 85C
20Vin @ ±40C
20Vin @ 25C
20Vin @ 85C
1.194
1.188
1.182
0.3
0.4
1
C006
Figure 18.
1.212
0.2
0.1
Load (A)
C007
Figure 17.
0.1
C003
Efficiency VOUT = 1.2 @ 85°C
90
Efficiency (%)
Efficiency (%)
Efficiency VOUT = 1.2
0.0
1
Figure 16.
90
0
0.001
0.1
Load (A)
0.5
0.6
0.7
0.5
0.4
0.3
0.2
0.8
0.1
Iout (m) | Load
C004
0.0
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Load (A)
Figure 19.
0.8
C005
Figure 20.
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TYPICAL CHARACTERISTICS (continued)
8
Startup 5VIN Full Load
Load Transient 12VIN 50-750mA
Figure 21.
Figure 22.
Shutdown 5VIN Full Load
Line Transient 9-15V 500mA Load
Figure 23.
Figure 24.
Switching Light Load
Switching Loaded
Figure 25.
Figure 26.
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TYPICAL CHARACTERISTICS (continued)
Short Circuit 12VIN
Short Circuit Recovery 12VIN
Figure 27.
Figure 28.
Thermal Shutdown
Thermal Shutdown Recovery
Figure 29.
Figure 30.
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FUNCTIONAL BLOCK DIAGRAM
Power
Good
Control
UVLO
Average
Threshold
Average Input
Current Detector
Soft Start
PG
VIN
Control Logic
Power Control
SW
Gate Drive
EN
+
Current Limit
Control
ILIM
Average
Threshold
Low Side
Current
Limit
Threshold
PGND
Direct Control
&
Compensation
VOUTS
+
Timer tON
-
FB
+
AGND
Theory of Operation
The LMR22007 is a buck regulator IC that delivers a 750 mA load current. The regulator has a preset switching
frequency of 2.1 MHz. This high frequency allows the LMR22007 to operate with small surface mount capacitors
and inductors, resulting in a DC-DC converter that requires a minimum amount of board space. The LMR22007
is internally compensated, which reduces design time, and requires few external components.
The following operating description of the LMR22007 will refer to the Block Diagram and to the waveforms in the
Figure below. The LMR22007 supplies a regulated output voltage by turning on the internal NMOS switch and
varying the on-time. During the on-time, the SW pin voltage VSW swings up to approximately VIN, and the
inductor current iL increases with a linear slope. The switch is turned off by the control logic. During the switch
off-time tOFF, inductor current discharges through the low side device, which forces the SW pin (VSW) to swing
below ground by the voltage drop across the low side device. The regulator loop adjusts the duty cycle (D) to
maintain a constant output voltage.
VOUT
D
VIN
10
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VSW
SW Voltage
D = tON / TSW
VIN
ttONt
0
-VD1
ttOFFt
t
tTSWt
Inductor Current
iL
ILPK
IOUT
tûiLt
0
t
The LMR22007 synchronous switched mode power converters are based on DCS-Control™ (Direct Control with
Seamless Transition into Power Save Mode), an advanced regulation topology, that combines the advantages of
hysteretic, voltage mode and current mode control including an AC loop directly associated to the output voltage.
This control loop takes information about output voltage changes and feeds it directly to a fast comparator stage.
It sets the switching frequency, which is constant for steady state operating conditions, and provides immediate
response to dynamic load changes. To get accurate DC load regulation, a voltage feedback loop is used. The
internally compensated regulation network achieves fast and stable operation with small external components
and low ESR capacitors.
The DCS-Control™ topology supports PWM (Pulse Width Modulation) mode for medium and heavy load
conditions and a Power Save Mode at light loads. During PWM, it operates at its nominal switching frequency in
continuous conduction mode. This frequency is typically about 2.1 MHz with a controlled frequency variation
depending on the input voltage. If the load current decreases, the converter enters Power Save Mode to sustain
high efficiency down to very light loads. In Power Save Mode the switching frequency decreases linearly with the
load current. Since DCS-Control™ supports both operation modes within one single building block, the transition
from PWM to Power Save Mode is seamless without effects on the output voltage.
Detailed Description of Pins and Key Functions
POWER SAVE MODE OPERATION
The LMR22007's built in Power Save Mode will be entered seamlessly, if the load current decreases. This
secures a high efficiency in light load operation. The device remains in Power Save Mode as long as the inductor
current is discontinuous.
In Power Save Mode the switching frequency decreases linearly with the load current maintaining high efficiency.
The transition into and out of Power Save Mode happens within the entire regulation scheme and is seamless in
both directions.
The LMR22007 includes a fixed on-time circuitry. This on-time, in steady-state operation, can be estimated as:
VOUT
t ON
u 478ns
VIN
(1)
For very small output voltages, an absolute minimum on-time of about 77ns is kept to limit switching losses.
Using tON, the typical peak inductor current in Power Save Mode can be approximated by:
(VIN VOUT ) u t ON
iLPSM(peak)
(2)
L
When VIN decreases to typically 15% above VOUT, the LMR22007 won't enter Power Save Mode, regardless of
the load current. The device maintains output regulation in PWM mode.
ENABLE (EN)
The simplest way to enable the operation of the LMR22007 is to connect the EN pin to VIN which allows self
start-up of the LMR22007 when the input voltage is applied. A resistor value of less than 3kΩ is recomended.
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Connect the EN pin to a voltage source greater than 0.9V to enable operation of the LMR22007. Apply a voltage
less than 0.4V to put the part into shutdown mode. In shutdown mode the quiescent current drops to typically
300nA. An internal pull-down resistor of about 400kΩ keeps EN logic low, if the pin is floating. The pull-down
resistor is disconnected if the pin is held High. During the soft start sequence the part will pull down with 2kΩ
from the EN pin to ground. To keep the part from turning itself off when using a pull-up resistor, the resistor
should be sized to keep the EN voltage above 0.9V when the UVLO threshold of the LMR22007 is reached. The
2kΩ is disconnected after start up.
When the rise time of VIN is longer than the soft-start time of the LMR22007 this method may result in an
overshoot in output voltage. In such applications, the EN pin voltage can be controlled by a separate logic signal,
or tied to a resistor divider, which reaches 0.9V after VIN is fully established. Connecting the EN pin to an
appropriate output signal of another power rail provides sequencing of multiple power rails. This will minimize the
potential for output voltage overshoot during a slow VIN ramp condition. Use the lowest value of VIN, seen in your
application when calculating the resistor network, to ensure that the 0.9V minimum EN threshold is reached.
INPUT CURRENT LIMIT and RLIM SECTION
The LMR22007 offers a user adjustable input current limit. Limiting the input current can be very useful when the
upstream power supply has a tight current budget. The input current limit can be set over a range of 150mA to
1000mA by connecting a resistor from 100kΩ to 15kΩ from pin B2 and ground. The higher the value of the RLIM
resistor, the lower the average input current limit.
When the output current increases, either from increased load current or charging of external capacitors during
start-up, the average input current will increase until it exceeds the set point. At this point the off time of the next
switching cycle will be lengthened to lower the average input current. This has the effect of lowering the
switching frequency and decreasing the duty cycle, thus lowering the output voltage. Although the average input
current is limited the peak switch current can still increase, this peak current is limited by the low side current
limit. A simplified equation for calculating the input current limit is shown below.
15000 Volts
Input Current Limit
RLIM
(3)
The input current limit is dependent on the delay of the comparator circuit (τ) and the inductor current ripple.
When we include these higher order terms into the equation for the current limit set resistor we get the following
equation.
15000 Volts
RLIM
(V VOUT ) u VOUT u W
Input Current Limit IN
VIN u L u K
(4)
Here, VIN is the input voltage where input current limit is most critical, VOUT is the output voltage set by the
feedback resistors, L is the value of the inductor in µH, η is converter efficiency found in the characteristic charts,
and the delay τ is a non linear factor with a typical value of 40ns.
The higher the ripple current in the inductor the more the input current limit will vary with input voltage. However,
variation of the input current limit is usually only significant when the inductor ripple current is comparable in
magnitude to the current limit to be set. Please refer to the characteristic curves for input current limit for more
details.
The input current limit also tends to move up as the input voltage increases. This effect becomes much more
significant as the device goes below 25% duty cycle.
LOW SIDE CURRENT LIMIT
The LMR22007 uses cycle-by-cycle current limiting to protect the output switches. During each switching cycle, a
current limit comparator detects if the low side device current exceeds the low side current limit. If the low side
current limit is exceeded the part skips the next on-time pulse until the current falls below the limit. This protects
the part from current run-away due to short circuits of the output.
12
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Product Folder Links: LMR22007
LMR22007
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SNVS985A – OCTOBER 2013 – REVISED OCTOBER 2013
SOFT-START
The LMR22007 has a fixed internal soft-start of 3.3 ms (typ). During soft-start, the error amplifier’s reference
voltage ramps from 0.0 V to its nominal value of 0.9 V in approximately 3.3 ms. This forces the regulator output
to ramp in a controlled fashion, which helps reduce inrush current. Upon soft-start the part will initially be in diode
emulation mode to avoid discharging a pre-biased load.
If the device is set to shutdown (EN
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