STw4141
Single-coil dual-output step-down DC/DC converter
for digital base band and multimedia processor supply
Features
■
Single coil dual output switching converter for
digital core supply & digital I/Os supply
– Digital I/O supply:V
OUT1
@ 200 mA
– CPU CORE supply:V
OUT2
@ 400 mA
Wide range of fixed output voltage
configurations available
High efficiency synchronous step down
converter with up to 92 % for the entire device
Size and cost optimized application board
(7x8 mm, height 1.2mm) three capacitors and
only one inductor necessary for both outputs
2.7 V to 5.5 V battery input range
±100mV output voltage accuracy full range in
PWM (Including Line and Load Transients)
900 kHz fixed frequency PWM operation
PFM mode operation at light load current
PWM/PFM switch can be done automatically or
forced by setting external pins (AUTO and
MODE/SYNC)
MODE/SYNC input pin for external clock
synchronization from 600 kHz to 1.5 MHz
VSEL input pin for V
OUT2
/V
OUT2(red.)
selection
Ultra low shutdown current (Iq<1 µA)
Short circuit and thermal shutdown protections
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Solution size
7 x 8 mm
■
■
■
TFBGA 3x3mm
16 bumps 0.5 mm pitch
Applications
Mobile phones
PDAs and hand held terminals
Portable media players
Digital still camera
WLAN and Bluetooth applications
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■
Description
The STw4141 is a single coil dual output
synchronous step down DC/DC converter that
requires only four standard external components.
It operates at a fixed 900 kHz switching frequency
in PWM mode. The device can operate in PFM
mode to maintain high efficiency over the full
range of output currents.
The STw4141 application requires a very small
PCB area and offers a very efficient, accurate,
space and cost saving solution to fulfill the
requirements of digital baseband or multimedia
processor supply (CORE & I/O).
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Application test circuit
L 4.7 µH
VLX1
V
IN
=2.7V to 5.5V
C
IN
10 µF
6.3 V
PVDD
B1
A2
VLX2
A3
A4
D1
VOUT1
FB1
C
OUT1
22 µF
6.3 V
V
OUT1
=1.8V
VDD
D3
EN
AUTO
D4
C2
STw4141
B4
D2
B2
B3
VOUT2
FB2
STATE
C
OUT2
22 µF
6.3 V
V
OUT2
=1.0V/1.2V
VSEL
MODE/SYNC
C3
C1
A1
C4
PGND GND
T_MODE
June 2006
Rev 2
1/30
www.st.com
1
Contents
STw4141
Contents
1
2
STw4141 pinout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
2.10
2.11
2.12
2.13
Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
DC electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Dynamic electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Soft start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Settling time of VOUT2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Line transients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Load transients in AUTO mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Load transients in PWM mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Switching between PFM and PWM in FORCED mode . . . . . . . . . . . . . . 14
Efficiency in PWM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Efficiency in AUTO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Output voltages versus output currents in PWM and PFM . . . . . . . . . . . . 17
3
Functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
PWM and PFM mode operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Current limiter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Short circuit protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Thermal shutdown protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
4
Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
4.1
4.2
4.3
4.4
4.5
4.6
User mode details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Automatic PWM/PFM mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
User selected PWM/PFM mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
External clock synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Checking transient response versus external components . . . . . . . . . . . 21
Bill of Material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.6.1
Inductor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
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STw4141
4.6.2
4.6.3
4.6.4
Contents
Input capacitor (CIN selection) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Output capacitors (COUT selection) . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Capacitors selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
4.7
PCB layout considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
4.7.1
4.7.2
PCB layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
TFBGA16 internal bumps access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
5
6
7
Package outline and mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Ordering information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
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List of tables
STw4141
List of tables
Table 1.
Table 2.
Table 3.
Table 4.
Table 5.
Table 6.
Table 7.
Table 8.
Table 9.
Table 10.
Table 11.
Table 12.
STw4141 pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Thermal data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
DC electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Dynamic electrical characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
STw4141 available user modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Operating mode information (STATE pin - digital output) . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Bill of material: inductor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Bill of Material: capacitor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
TFBGA 3x3x1.20 16 F4x4 0.50. Package code: L0 - JEDEC/EAIJ . . . . . . . . . . . . . . . . . . 26
STw4141 order codes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
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STw4141
List of figures
List of figures
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Figure 9.
Figure 10.
Figure 11.
Figure 12.
Figure 13.
Figure 14.
Figure 15.
Figure 16.
Figure 17.
Figure 18.
Figure 19.
Figure 20.
Pin assignment in TFBGA 3x3 mm - 16 bumps 0.5 mm pitch . . . . . . . . . . . . . . . . . . . . . . . 6
Smooth start-up sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Settling time of VOUT2, IOUT1 = 200mA, IOUT2 = 400mA . . . . . . . . . . . . . . . . . . . . . . . . 11
Line transient, VOUT1 = 1.8V @ 100mA, VOUT2 = 1.2V @ 100mA . . . . . . . . . . . . . . . . . 12
Load transient in AUTO mode VIN = 3.6V, VOUT1 = 1.8V, VOUT2 = 1.2V . . . . . . . . . . . . 12
Load transient in PWM mode, IOUT1 = 1mA to 200mA, IOUT2 = 1mA to 400mA. . . . . . . 13
Switching between PFM to PWM - VIN = 3.6V, IOUT1 = 10mA, IOUT2 = 10mA. . . . . . . . 14
Switching between PWM to PFM - VIN = 3.6V, IOUT1 = 10mA, IOUT2 = 10mA. . . . . . . . 14
Switching regulator efficiency in PWM mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Switching regulator efficiency in auto mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Output voltages versus output currents in PWM and PFM . . . . . . . . . . . . . . . . . . . . . . . . . 17
Automatic PWM/PFM switch schematic example. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
PWM/PFM forced mode schematic example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Application using external clock synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Board layout track length and width . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Demoboard top layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Demoboard assembled with 22 µF output capacitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
TFBGA16 ball pad spacing and track parameters to internal pads . . . . . . . . . . . . . . . . . . 24
PCB routing example using TFBGA16 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
TFBGA 3x3x1.20 16 F4x4 0.50 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
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京公网安备 11010802033920号
EEWORLD
