PM8903A
3 A step-down monolithic switching regulator
Datasheet
−
production data
Features
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Integrated 35 mΩ MOSFETs for high efficiency
3 A continuous output current
2.8 V to 6 V input voltage (V
IN
)
2.9 V to 5.5 V supply voltage (V
CC
)
Adjustable output voltage down to 0.6 V
1% output voltage accuracy
1.1 MHz switching frequency operation
PSKIP mode to optimize light load efficiency
Embedded bootstrap diode
Thermally compensated loss-less current
sense across HS and LS MOSFETs
OV/UV/OC and overtemperature protection
Internal soft-start and soft-stop
Interleaving synchronization (up to 2 ICs)
Power Good output
Shutdown function (< 15 µA quiescent current)
VFQFPN16 3 x 3 mm compact package
The PM8903A features low-resistance integrated
nMOS and proprietary pulse-skipping mode for
optimum efficiency over all the loading range.
The voltage mode control loop allows the widest
range of output filters. Current sense is internally
thermally compensated for optimum precision.
The integrated 0.6 V reference allows the
regulation of output voltages with ±1% accuracy
over temperature variations. Switching frequency
is typically set to 1.1 MHz and can be
programmed to 0.8 MHz or 1.0 MHz. Out of phase
synchronization allows the reduction of input RMS
current.
The PM8903A provides precise dual-threshold
overcurrent protection as well as
over/undervoltage and overtemperature
protection. PGOOD output easily provides real-
time information on the output voltage.
The PM8903A is available in VFQFPN16 3 x 3
mm.
VFQFPN16 (3 x 3 mm)
Applications
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Subsystem power supply
CPU, DSP and FPGA power supplies
Distributed power supply
General DC-DC converters
Description
The PM8903A is a high efficiency monolithic step-
down switching regulator designed to deliver up to
3 A continuous current. The IC operates from 2.8
V to 6 V input voltage (V
IN
).
Table 1.
Device summary
Order codes
PM8903A
PM8903ATR
January 2013
This is information on a product in full production.
Package
VFQFPN16 (3 x 3 mm)
VFQFPN16 (3 x 3 mm)
Doc ID 024147 Rev 1
Packaging
Tube
Tape and reel
1/33
www.st.com
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Contents
PM8903A
Contents
1
Typical application circuit and block diagram . . . . . . . . . . . . . . . . . . . . 3
1.1
1.2
Application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2
Pin description and connection diagrams . . . . . . . . . . . . . . . . . . . . . . . 4
2.1
Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3
4
Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Electrical specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.1
4.2
4.3
4.4
Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Recommended operating conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Typical operating characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5
Device description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5.1
5.2
Power section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Startup and shutdown management . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.2.1
5.2.2
Low-side-less startup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Soft-off . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
5.3
Output voltage monitoring and protection . . . . . . . . . . . . . . . . . . . . . . . . 14
5.3.1
5.3.2
5.3.3
5.3.4
Overvoltage protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Undervoltage protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Feedback disconnection protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Power Good (PGOOD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5.4
5.5
5.6
5.7
5.8
Overcurrent protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Overtemperature protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Pulse-skipping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Multifunction pin PSKIP/MS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
6
Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
6.1
Compensation network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
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Doc ID 024147 Rev 1
PM8903A
Contents
6.2
6.3
6.4
6.5
Output voltage setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Inductor design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Output capacitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Input capacitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
7
PM8903A demonstration board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
7.1
Detailed demonstration board description . . . . . . . . . . . . . . . . . . . . . . . . 24
7.1.1
7.1.2
7.1.3
7.1.4
Power input (V
IN
) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Signal input (V
CC
) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Output (V
OUT
) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Test points and jumper connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
8
9
Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Doc ID 024147 Rev 1
3/33
Typical application circuit and block diagram
PM8903A
1
1.1
Typical application circuit and block diagram
Application circuit
Figure 1.
Typical application circuit
1.2
Block diagram
Figure 2.
Block diagram
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Doc ID 024147 Rev 1
PM8903A
Pin description and connection diagrams
2
Pin description and connection diagrams
Figure 3.
Pin connection (top view)
EN
SYNCH
PGOOD
BOOT
PGND
PGND
VIN
VIN
16
1
2
3
4
5
6
7
8
15
14
13
12
11
10
9
VCC
GND
FB
COMP
2.1
Pin description
Table 2.
Pin #
1
Pin description
Name
EN
Function
Enable. Internally pulled up by 5 µA to V
CC
.
Force low to disable the device, set free or pull up above turn-on threshold to
enable the converter operations.
Synchronization pin.
According to PSKIP status, the IC sends the synchronization signal out of this
pin when master, while accepting a synchronization signal when slave.
Connect to the same SYNCH pin of a similar part when synchronizing ICs.
In case of single IC operation, leave floating.
Open drain output set free after SS has finished and pulled low when V
OUT
is
out of the PGOOD window or any protection is triggered.
Pull up to a voltage lower than V
CC
, if not used it can be left floating.
Bootstrap pin.
It provides power supply for the floating high-side driver. Connect with 0.1 µF
to PHASE. See
Figure 1.
Output inductor connection.
The pins are connected to the embedded MOSFETs (high-side source and
low-side drain). Connect directly to output inductor. See
Figure 1.
2
SYNCH
3
PGOOD
4
BOOT
5 to 7
PHASE
8
Pulse-skip and master/slave definition.
Connect with a resistor to GND or leave it floating to define:
Pulse-skip feature status;
PSKIP / MS
Master/slave for synchronization;
Switching frequency.
See
Section 5.8 on page 17.
Doc ID 024147 Rev 1
PHASE
PHASE
PHASE
PSKIP / MS
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