SP6122 Datasheet, PDF (9/19 Pages) Sipex Corporation – Low Voltage, Micro 8, PFET, Buck Controller Ideal for 1A to 5A, Small Footprint, DC-DC Power Converters

As an SP6122 application example, we will
use the circuit from the SP6122 Evaluation
Board Manual. This evaluation board uses
the Sipex SP6122ACU, 1.25V adjustable
PFET controller to realize a 3.3V to 1.9V
step down converter. The board is opti-
mized for 1A – 4A operation and has an
R_DS(ON) over current trip threshold of about
APPLICATION INFORMATION
7A. The body of the applications section
contains:
• Data for the Evaluation Board
• Guidelines for Component Selection
• Features and Protection
• Layout Guidelines
• Introduction to the “Buck Cad Calculator”
Spreadsheet
+3.3V
V_IN
FFLAG
J1
1
2 _ENABLE
3 ^CEN
4.7nF
GND
+
C1
4.7µF
Ceramic
C_IN
47µF
Ceramic
1 _VCC
2 _FFLAG
3 _VOUT
4 _ENABLE
PDRV ⁸
®
GND ⁷
SP6122
I_SET ⁶
I_SENSE ⁵
Q1
PMOS
PDS6375
RS
1.00k
2.2µH
L1
DS
STPS2L25U
V_OUT ^+1.9V
V_OUT
R1
6.5k
+
C_OUT
470µF
R2
12.5k
Figure 1. SP6122 Evaluation Board Application Schematic
Data For Evaluation Board
The SP6122 is engineered for size and mini-
mum pin count, yet has a very accurate 2.0%
89
reference over line, load and temperature.
88
Figure 2 data shows a typical SP6122 Evalu-
87
ation Board Efficiency plot, with efficiencies to
88% and output currents to 4A. Load Regula-
86
tion plot in Figure 3 shows an essentially flat
85
response of only 3mV change for up to 4A
load. Figure 4 Line Regulation illustrates a
84
1.90V output that varies only 4mV or 0.2% for
an input voltage change from 3.0V to 5.5V.
83
0
1
2
3
4
5
While data on individual power supply boards
ILOAD (A)
may vary, the capability of the SP6122 of
achieving high accuracy over load and line
shown here is quite impressive and desirable
Figure 2. SP6122 Efficiency with V_IN = 3.3V,
V_OUT = 1.9V.
for accurate power supply design.
Rev. 7/16/03
SP6122 Low Voltage, Micro 8, PFET, Buck Controller
9
© Copyright 2003 Sipex Corporation