Data Brief
For further information contact your local STMicroelectronics sales office.
May 2008 Rev 1 1/4
4
STEVAL-ISA052V2
Evaluation board for the PM6675AS high efficiency
step-down controller with embedded 2 A LDO regulator
Features
■4.5 V to 36 V input voltage range
■0.6 V, ±1% voltage reference
■1.5 V fixed output voltage
■0.6 V to 3.3 V adjustable output voltage
■1.237 V ±1% reference voltage available
■Very fast load transient response using
constant on-time (COT) control loop
■No RSENSE current sensing using RDS(ON) of
the low-side MOSFETs
■Negative current limit
■Latched OVP, UVP and thermal shutdown
■Fixed 3 ms soft-start
■Selectable pulse-skipping at light load
■Selectable no-audible (33 kHz) pulse-skip
mode
■All ceramic output capacitors application
supported
■Output voltage ripple compensation
■Output soft-end
Description
This evaluation board is based on the PM6675AS
device, which consists of a single high efficiency
step-down controller and an independent low-
dropout (LDO) linear regulator.
The constant on-time (COT) architecture assures
fast transient response supporting both
electrolytic and ceramic output capacitors. An
embedded integrator control loop compensates
the DC voltage error due to the output ripple.
Selectable low-consumption mode allows the
highest efficiency over a wide range of load
conditions. The low-noise mode sets the minimum
switching frequency to 33 kHz for audio-sensitive
applications. The LDO linear regulator can sink
and source up to 2 Apk. Two fixed current limits
(±1 A and ±2 A) can be chosen.
An active soft-end is independently performed on
both the switching and the linear regulator outputs
when disabled.
STEVAL-ISA052V2
www.st.com
Circuit schematic STEVAL-ISA052V2
2/4
1 Circuit schematic
Figure 1. Schematic diagram
0 0
J2
VOUT
1
J3
PGND
1
J9
PGND 1
J1
VIN
1
J5
VCC 1
JP3
VSE
VSE
L
0
0
0
U1
PM66
66
75S
LOUT 24
LIN 23
BOOT 22
HGATE 21
PHAS
AS
E20
CSNS 19
VCC 18
LGATE 17
PGND 16
SP
SP
G15
LEN 14
SWEN 13
LILIM
12 COMP
11 VSE
VSE
L
10 VS
VS
NS
9VOSC
8VREF
7
AV
AV
CC
6SGND
5LPG
4NOSK
SK
IP
3LFB
2LGND
1
THPD
25
J10
VCCGND 1
Q2
S12NH3LL
5
4
1
6
7
8
2
3
Q1
S12NH3LL
5
4
1
6
7
8
2
3
J11
LGND 1
J6
LIN 1
2x UMK325BJ106KM-T
R19
7.5k
R20
10k
D1
BA
BA
T54J
21
R4 3R 3
1 2
0
R3 1. 2k
1 2
R1 330k
1 2
R2
18k
12
L1 0.9u
1 2
D2
2 1
C21
100p
12
C1
10u
12
C2
10u
12
C3
220u
12
C4
22
22
0u
12
C10
12
C9
100n
12
C22
100p
12
R7
3R9
12
0
C19
N. M.
12
0
C13
100n
1 2
C20
N. M.
12
SW1
1
2
4
3
R11 100k
1 2
R12 100k
1 2
R18
100k
0
0
VCC
R14 7.5k R15 6.8k
C15 6.8n
1 2
C16 680p
1 2
C17
N. M.
12
C6
10u
12
R17 0
VCC
VCC
VCC
VCC
C11
10u
12
C14
100n
12
TP1
GND _TP
J4
SP
SP
G
1
R13
100k
12
0
C5
1u
12
JP5
IN T-VE
VE
SR
JP2
LILIM
1 2
3 4
5 6
JP1
NOSK
SK
IP
1 2
3 4
5 6
D3
STPS
PS
1L30A
2 1
0
0
C7
10u
12
0
0
R8
12k
R9
13k
R6
0
STPS1L30M
R10
0
MLC1240-901ML
2x 4TPE220MF
C12
100n
12
LEN-SWEN
J7
LOUT 1
J8
LPG 1C18
1n
12
R16
4R7
0 0
STEVAL-ISA052V2 Revision history
3/4
2 Revision history
Table 1. Document revision history
Date Revision Changes
05-May-2008 1 Initial release.
STEVAL-ISA052V2
4/4
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