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LM26480Externally Programmable Dual High-Current Step-Down DC/DC and Dual Linear
Regulators
July 7, 2008
LM26480
Externally Programmable Dual High-Current Step-Down
DC/DC and Dual Linear Regulators
General Description
The LM26480 is a multi-functional Power Management Unit,
optimized for low-power digital applications. This device inte-
grates two highly efficient 1.5A step-down DC/DC converters
and two 300 mA linear regulators. The LM26480 is offered in
a tiny 4 x 4 x 0.8mm LLP-24 pin package.
Linear Regulators (LDO)
■
V
OUT
of 1.0V–3.5V
■
±3% FB voltage accuracy
■
300 mA output current
■
25 mV (typ) dropout
Key Specifications
Step-Down DC/DC Converter (Buck)
■
1.5A output current
■
V
OUT
from:
—
Buck1 : 0.8V–2.0V @ 1.5A
—
Buck2 : 1.0V–3.3V @ 1.5A
■
Up to 96% efficiency
■
±3% FB voltage accuracy
■
2 MHz PWM switching frequency
■
PWM - PFM automatic mode change under low loads
■
Automatic soft start
Features
■
Compatible with advanced applications processors and
■
■
■
■
■
■
■
FPGAs
2 LDOs for powering Internal processor functions and I/Os
Precision internal reference
Thermal overload protection
Current overload protection
24-lead 4 × 4 × 0.8mm LLP package
External Power-On-Reset function for Buck1 and Buck2
Undervoltage lock-out detector to monitor input supply
voltage
Applications
■
Core digital power
■
Applications processors
■
Peripheral I/O power
Typical Application Circuit
30040401
© 2008 National Semiconductor Corporation
300404
www.national.com
LM26480
30040402
FIGURE 1. Application Circuit
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2
LM26480
Connection Diagrams and Package Mark Information
30040403
FIGURE 2. 24-Lead LLP Package (top view)
Note:
The physical placement of the package marking will vary from part to part.
(*) UZXYTT format: ‘U’ – wafer fab code; ‘Z’ – assembly code; ’XY’ 2 digit date code; ‘TT” – die run code. See http://www.national.com/quality/
marking_conventions.html for more information on marking information.
Part Number
LM26480SQ-AA
LM26480SQX-AA
Spec
NOPB
NOPB
Quantity
1000 tape and reel
4500 tape and reel
3
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LM26480
Pin Descriptions
LLP Pin No.
1
2
Name
VINLDO12
SYNC
I/O
I
I
Type
PWR
G/(D)
Description
Analog Power for Internal Functions (VREF, BIAS, I
2
C, Logic)
Frequency Synchronization pin which allows the user to connect an
external clock signal to synchronize the PMIC internal oscillator.
Default OFF and must be grounded when not used. Contact National
Sales office to enable.
nPOR Power on reset pin for both Buck1 and Buck 2. Open drain logic
output 100K pullup resistor. nPOR is pulled to ground when the
voltages on these supplies are not good. See nPOR section for more
info.
Buck1 NMOS Power Ground
Buck1 switcher output pin
Power in from either DC source or Battery to Buck1
Enable Pin for Buck1 switcher, a logic HIGH enables Buck1. Pin cannot
be left floating.
Buck1 input feedback terminal
Non-switching core ground pin
Analog Power for Buck converters
Buck2 input feedback terminal
Enable Pin for Buck2 switcher, a logic HIGH enables Buck2. Pin cannot
be left floating.
Power in from either DC source or Battery to Buck2
Buck2 switcher output pin
Buck2 NMOS
LDO2 enable pin, a logic HIGH enables LDO2. Pin cannot be left
floating.
LDO1 enable pin, a logic HIGH enables LDO1. Pin cannot be left
floating.
LDO ground
Power in from either DC source or battery to LDO1
LDO1 Output
LDO1 Feedback Terminal
LDO2 Feedback Terminal
LDO Output
Power in from either DC source or battery to LDO2.
Connection isn't necessary for electrical performance, but it is
recommended for better thermal dissipation.
I:
Input Pin
I/O:
Input/Output Pin
O:
Output Pin
3
NPOR
O
D
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
DAP
A:
Analog Pin
GND_SW1
SW1
VIN1
ENSW1
FB1
GND_C
AVDD
FB2
ENSW2
VIN2
SW2
GND_SW2
ENLDO2
ENLDO1
GND_L
VINLDO1
LDO1
FBL1
FBL2
LDO2
VINLDO2
DAP
D:
Digital Pin
G
O
I
I
I
G
I
I
I
I
O
G
I
I
G
I
O
I
I
O
I
GND
G:
Ground Pin
G
PWR
PWR
D
A
G
PWR
A
D
PWR
PWR
G
D
D
G
PWR
PWR
A
A
PWR
PWR
GND
PWR:
Power Pin
Power Block Operation
Power Block Input
VINLDO12
AVDD
VIN1
VIN2
VINLDO1
VINLDO2
Enabled
VIN+
VIN+
VIN+
VIN+
Disabled
VIN+
VIN+
VIN+ or 0V
VIN+ or 0V
Note
Always Powered
Always Powered
≤
VIN+
≤
VIN+
≤
VIN+
≤
VIN+
If Enabled, Min VIN is 1.74V
If Enabled, Min VIN is 1.74V
VIN+ is the largest potential voltage on the device.
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