ST2S08B [STMICROELECTRONICS]
Dual synchronous rectification, 1.5 A, 1.5 MHz adjustable step-down switching regulator; 双通道同步整流， 1.5 A ， 1.5 MHz的可调降压型开关稳压器
| 型号： | ST2S08B |
| 厂家： | 
ST |
| 描述： | Dual synchronous rectification, 1.5 A, 1.5 MHz adjustable step-down switching regulator |
| 文件： | 总18页 (文件大小：757K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
ST2S08B
Dual synchronous rectification, 1.5 A, 1.5 MHz
adjustable step-down switching regulator
Datasheet − production data
Features
■ Step-down current mode PWM (1.5 MHz) DC-
DC converter
■ Adjustable output voltage from 0.8 V
■ 2 % DC output voltage tolerance
■ Synchronous rectification
■ Integrated current limit
QFN12L (4 x 4 mm)
■ Inhibit function
■ Soft-start for start delay of 800 µs typ.
■ Typical efficiency: > 80 % at VOUT = 1.2 V
■ 1.5 A output current capability
ST2S08B is available in the QFN12L (4 x 4 mm)
package.
■ Non-switching quiescent current: max 1.5 mA
over temperature range
■ RDS(ON) 150 mΩ (typ.)
■ Uses tiny capacitors and inductors
■ Available in QFN12L (4 x 4 mm)
Description
The ST2S08B is a dual step-down DC-DC
converter optimized for powering low-voltage
digital cores in ODD applications and, generally,
to replace the high current linear solution when
the power dissipation may cause a high heating of
the application environment. It provides up to 1.5
A over an input voltage range of 3 V to 5.5 V. A
high switching frequency of 1.5 MHz allows the
use of tiny surface-mounted components as well
as a resistor divider to set the output voltage
value. Only an inductor and two capacitors are
required. A low output ripple is guaranteed by the
current mode PWM topology and the utilization of
low ESR SMD ceramic capacitors. The device is
thermally protected and current limited. The
Table 1.
Device summary
Order code
Package
Packaging
ST2S08BPQR
QFN12L (4 x 4 mm)
Tape and reel
May 2012
Doc ID 18290 Rev 2
1/18
This is information on a product in full production.
www.st.com
18
Contents
ST2S08B
Contents
1
2
3
4
5
6
7
8
Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Typical application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Typical performance characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
General information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
8.1
8.2
8.3
8.4
8.5
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Programming the output voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Inductor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Input and output capacitor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Layout considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
9
Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
10
2/18
Doc ID 18290 Rev 2
ST2S08B
1
Diagram
Diagram
Figure 1.
Schematic diagram
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* Not available on the ST2S08B version.
Doc ID 18290 Rev 2
3/18
Pin configuration
ST2S08B
2
Pin configuration
Figure 2.
Pin connections (top view)
Table 2.
Pin n°
Pin description
Name
Function
1
2
3
4
5
6
7
8
9
HV
FB2
Programing pin. It must be floating or connected to GND.
Feedback voltage
GND2
SW2
Power ground
Switching pin
VIN_SW
SW1
Power input voltage pin
Switching pin
GND1
FB1
Power ground
Feedback voltage/output voltage
Not connect
NC
Inhibit pin:
10
INH
- High device on
- Low device off
11
12
VIN_A
Supply for analog circuit
System ground
GND_A
4/18
Doc ID 18290 Rev 2
ST2S08B
3
Maximum ratings
Maximum ratings
Table 3.
Absolute maximum ratings
Symbol
VIN_SW
Parameter
Value
Unit
Positive power supply voltage
Positive power supply voltage
Inhibit voltage
-0.3 to 7
-0.3 to 7
-0.3 to 7
-0.3 to 7
V
V
V
V
VIN_A
VINH
SWITCH voltage Max. voltage of output pin
VFB1,2 Feedback voltage/output voltage
Current into VFB pin Common mode input voltage
-0.3 to 2.5
+1 to -1
150
V
mA
°C
°C
°C
TJ
Max junction temperature
TSTG
TLEAD
Storage temperature range
-65 to +150
300
Lead temperature (soldering) 10 sec.
Note:
Absolute maximum ratings are those values beyond which damage to the device may occur.
Functional operation under these conditions is not implied.
Table 4.
Symbol
Thermal data
Parameter
Thermal resistance junction-case
Value
Unit
RthJC
RthJA
10
60
°C/W
°C/W
Thermal resistance junction-ambient
Table 5.
ESD performance
Parameter
Symbol
Test conditions
HBM-DH11C
Value
Unit
kV
ESD
ESD protection voltage
4
Doc ID 18290 Rev 2
5/18
Electrical characteristics
ST2S08B
4
Electrical characteristics
VIN_SW = VIN_A = 5 V, VO1,2 =1.2 V, C1= 4.7 µF, C2 = C3 = 22 µF, L1 = L2 = 3.3 µH,
TJ = -30 to 125 °C, unless otherwise specified. Typical values refer to 25 °C.
Table 6.
Symbol
Electrical characteristics
Parameter
Test conditions
Min.
Typ.
Max.
Unit
FB1,2
IFB1,2
Feedback voltage
784
800
816
600
1.5
mV
nA
VFB pin bias current
VFB = 1 V
VINH > 1.2 V, VFB = 1 V
VINH = GND
mA
µA
IQ
Quiescent current
20
VIN = 3.0 to 5.5 V (1)
TJ = - 30 to 85 °C
,
IO1,2
IMIN
Output current
1.5
A
Minimum output current
1
mA
3.0 V < VIN < 5 V
3.0 V < VIN < 5.5 V
Device OFF
1.2
1.3
VINH
Inhibit threshold
V
0.4
2
IINH1,2
Inhibit pin current
µA
%VO1,2
ΔVIN
/
%VO/
VIN
Reference line regulation
3.0 V < VIN < 5.5 V
10 mA < IO < 1.5 A
0.04
ΔVO1,2
Reference load regulation
PWM switching frequency
Maximum duty cycle
10
1.5
94
mV
MHz
%
PWM fS
DMAX
ISWL
VFB = 0.7 V, TA = 25 °C
1.2
85
1.8
VFB = 0.7 V, TA = 25 °C
(2)
Switching current limitation
NMOS leakage current
PMOS leakage current
2
A
ILKN
VFB = 0.9 V, TA = 25 °C
VFB = 0.9 V, TA = 25 °C
0.1
0.1
0.15
0.2
75
µA
µA
Ω
ILKP
R
DSon-N NMOS switch on resistance ISW = 250 mA
DSon-P PMOS switch on resistance ISW = 250 mA
0.3
0.4
R
Ω
IO = 20 mA to 100 mA
O = 100 mA to 1.5 A
%
η
Efficiency
I
80
%
TSHDN
THYS
Thermal shutdown
150
°C
Thermal shutdown
hysteresis
15
°C
V
ISC - VIN Short-circuit VIN range (2)
Output short-circuit to ground
3
5.3
1. V = 90 % of nominal value.
O
2. Guaranteed by design, but not tested in production.
6/18
Doc ID 18290 Rev 2
ST2S08B
Typical application
5
Typical application
Application circuit
VIN_A
Figure 3.
VIN
L2
3.3 µH
SW2
R3
VO2
VFB2
VIN_SW
L1
3.3 µF
ST2S08B
SW1
INH
NC
R1
VO1
VFB1
GND1 GND2 HV
GND_A
C1
C2
22 µF
R2
4.7 µF
C3
22 µF
R4
AM07870v1
Note:
R1, R2 and R3, R4 are calculated according to the following equations:
- VO1 = VFB1 (1 + R1 / R2)
- VO2 = VFB2 (1 + R3 / R4)
Doc ID 18290 Rev 2
7/18
Typical performance characteristics
ST2S08B
6
Typical performance characteristics
Figure 4.
Feedback voltage vs. temperature Figure 5.
Efficiency vs. output current 1
AM07883v1
0.84
0.83
0.82
0.81
0.8
AM07884v1
100
VIN = 5 V, Vfb1,Vfb2 connected to VO1-2 , IO1 = IO2 = 10 mA
90
80
70
60
50
40
30
20
10
0
0.79
0.78
0.77
0.76
-50
VIN = 5 V, VO1 = 1.2 V, VO2 NO LOAD
-25
0
25
50
75
100
125
0
0.25
0.5
0.75
1
1.25
1.5
Temperature [°C]
Output current 1 [A]
Figure 6.
Efficiency vs. output current 2
Figure 7.
Switching frequency vs.
temperature
AM07885v1
AM07886v1
100
90
80
70
60
50
40
30
20
10
1.9
1.8
1.7
1.6
1.5
1.4
1.3
1.2
VIN = 5 V, VO2 = 3.3 V, VO1 NO LOAD
VIN = 5 V, VFB1 = VFB2 = 0.7 V
1.1
-50
0
0
-25
0
25
50
75
100
125
0.25
0.5
0.75
1
1.25
1.5
Temperature [°C]
Output Current 2 [A]
Figure 8.
Duty cycle vs. temperature
Figure 9.
Inhibit threshold vs. temperature
AM07887v1
AM07889v1
100
98
96
94
92
90
88
86
84
82
1.4
1.2
1
0.8
0.6
0.4
0.2
ON
VIN = 5 V, VFB1 = VFB2 = 0.7 V
VIN = 5.5 V , IO1 =IO2 = 100 mA
OFF
0
80
-50
-25
0
25
50
75
100
125
-50
-25
0
25
50
75
100
125
T [°C]
Temperature [°C]
8/18
Doc ID 18290 Rev 2
ST2S08B
Typical performance characteristics
Figure 10. Switching current limitation vs.
temperature
Figure 11. Load transient response
AM07888v1
2.4
2.2
2
1.8
1.6
1.4
1.2
1
0.8
0.6
VIN = 5 V, Output1 maximum load current
-50
-25
0
25
50
75
100
125
Temperature [°C]
V
= 5 V, I from 250 mA to 1.5 A V @ 1.2 V
O1 O1
IN
Figure 12. Inhibit transient
INH
V
= from 0 V to 2 V, V = 5.5 V, I = I = 1.5 A
IN O1 O2
INH
Doc ID 18290 Rev 2
9/18
General information
ST2S08B
7
General information
The ST2S08B is a dual adjustable current mode PWM step-down DC-DC converter.
It is a complete 1.5 A switching regulator with internal compensation that eliminates the
need for additional components.
The constant frequency, current mode, PWM architecture and stable operation with ceramic
capacitors, results in low, predictable output ripple.
To clamp the error amplifier reference voltage, a soft-start control block, generating a
voltage ramp, has been implemented. Other circuits fitted to the device protection are the
thermal shut-down block, which turns off the regulator when the junction temperature
exceeds 150 °C (typ.), and cycle-by-cycle switching current limiting.
Operation of the device requires few components: 2 inductors, 3 capacitors, and a resistor
divider. The chosen inductor must be capable of not saturating at the peak current level. Its
value should be selected keeping in mind that a large inductor value increases the efficiency
at low output current and reduces output voltage ripple, while a smaller inductor can be
chosen when it is important to reduce package size and total application cost.
Finally, the ST2S08 has been designed to work properly with X5R or X7R SMD ceramic
capacitors both at input and at output. These types of capacitors, due to their very low series
resistance (ESR), minimize the output voltage ripple. Other low ESR capacitors can be
used, according to the needs of the application, without compromising the correct
functioning of the device.
10/18
Doc ID 18290 Rev 2
ST2S08B
Application information
8
Application information
8.1
8.2
Introduction
The following technical information is used for estimating typical external component
characteristics using standard equations. Nevertheless, it is strongly recommended to
validate the suitability of external components to the application requirements by thoroughly
testing any solution at bench level on a real evaluation circuit.
Programming the output voltage
The output voltage for both channels can be adjusted from 0.8 V up to 85 % of the input
voltage value by connecting a resistor divider between VO and GND, the middle point of the
divider must be connected to the feedback (FB) pin, as shown in Figure 3.
The resistor divider must be chosen according to the following equations:
Equation 1
⎛
R1 ⎞
V
= V
× 1+
⎜
⎟
⎟
O1
FB1
⎜
⎝
R2
⎠
Equation 2
⎛
R3 ⎞
V
= V
× 1+
⎜
⎟
⎟
O2
FB2
⎜
⎝
R4
⎠
Using a resistor with a value in the range of 1 kΩ to 50 kΩ is recommended. Lower values
are also suitable, but increase current consumption.
8.3
Inductor selection
The inductor is the key passive component for switching converters.
The critical inductance values can then be obtained according to the following formulas:
Equation 3
V ×(V
− V )
O
O
IN_MAX
L
=
MIN
V
×F
× ΔI
IN_MAX
SW L
F
SW = switching frequency
ΔIL = the peak-to-peak inductor ripple current. As a rule of thumb, the peak-to-peak ripple
can be set at 20 % - 40 % of the output current.
The peak current of the inductor can be calculated as:
Doc ID 18290 Rev 2
11/18
Application information
Equation 4
ST2S08B
V ×(V
− V )
O
O
IN_MAX
I
= (I /0.8)+
O
PEAK
2×V
×F
×L
IN_MAX SW
In addition to the inductance value, in order to avoid saturation, the maximum saturation
current of the inductor must be higher than that of the IPEAK
.
8.4
Input and output capacitor selection
It is recommended to use ceramic capacitors with X5R or X7R dielectric and low ESR as
input and output capacitors, in order to filter any disturbance present in the input line and to
obtain stable operation. The output capacitor is very important for satisfying the output
voltage ripple requirements.
The output voltage ripple (VO_RIPPLE), in continuous mode, for the step-down channel, can
be calculated as:
Equation 5
⎡
⎤
⎥
⎦
1
V
= ΔI × ESR+
⎢
⎣
O_RIPPLE
L
8× C
×F
OUT SW
where Δ IL is the ripple current and FSW is the switching frequency.
The use of ceramic capacitors with voltage ratings in the range higher than 1.5 times the
maximum input or output voltage is recommended.
8.5
Layout considerations
Due to the high switching frequency and peak current, the layout is an important design step
for all switching power supplies. Important parameters (efficiency, output voltage ripple,
switching noise immunity, etc.) can be affected if the PCB layout is not designed paying
close attention to the following DC-DC general layout rules:
●
Short, wide traces must be implemented for mains current and for power ground paths.
The input capacitor must be placed as close as possible to the IC pins as well as the
inductor and output capacitor.
●
The FB pin connection to the external resistor divider is a high impedance node, so
interference can be minimized by placing the routing of the feedback node as far as
possible from the high current paths. To reduce pick-up noise, the resistor divider must
be placed very close to the device.
●
●
A common ground node minimizes ground noise.
The exposed pad of the package must be connected to the common ground node.
Moreover, the exposed pad ground connection must be properly designed in order to
facilitate heat dissipation from the exposed pad to the ground layer using PCB vias.
12/18
Doc ID 18290 Rev 2
ST2S08B
Package mechanical data
9
Package mechanical data
In order to meet environmental requirements, ST offers these devices in different grades of
ECOPACK® packages, depending on their level of environmental compliance. ECOPACK
specifications, grade definitions, and product status are available at: www.st.com.
ECOPACK is an ST registered trademark.
Doc ID 18290 Rev 2
13/18
Package mechanical data
ST2S08B
QFN12L (4x4) mechanical data
mm.
inch.
Typ.
Dim.
Min.
Typ.
0.90
0.02
0.20
0.30
4.00
2.15
4.00
2.15
0.80
0.55
Max.
1.00
0.05
Min.
Max.
0.039
0.002
A
A1
A3
b
0.80
0.031
0.035
0.001
0.008
0.012
0.157
0.085
0.157
0.085
0.031
0.022
0.25
3.90
2.00
3.90
2.00
0.35
4.10
2.25
4.10
2.25
0.010
0.154
0.079
0.154
0.079
0.014
0.161
0.089
0.161
0.089
D
D2
E
E2
e
L
0.45
0.65
0.018
0.026
7936361B
14/18
Doc ID 18290 Rev 2
ST2S08B
Package mechanical data
Tape & reel QFNxx/DFNxx (4x4) mechanical data
mm.
Typ.
inch.
Typ.
Dim.
Min.
Max.
330
Min.
Max.
12.992
0.519
A
C
12.8
20.2
99
13.2
0.504
0.795
3.898
D
N
101
3.976
T
14.4
0.567
Ao
Bo
Ko
Po
P
4.35
4.35
1.1
4
0.171
0.171
0.043
0.157
0.315
8
Doc ID 18290 Rev 2
15/18
Package mechanical data
ST2S08B
Figure 13. QFN12L (4 x 4 mm) footprint recommended data
16/18
Doc ID 18290 Rev 2
ST2S08B
10
Revision history
Revision history
Table 7.
Document revision history
Revision
Date
Changes
30-Nov-2010
18-May-2012
1
2
Initial release.
Modified max 1.0 mA ==> max 1.5 mA : Features on page 1.
Doc ID 18290 Rev 2
17/18
ST2S08B
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18/18
Doc ID 18290 Rev 2
相关型号：
ST2S08BPQR
Dual synchronous rectification, 1.5 A, 1.5 MHz adjustable step-down switching regulator
STMICROELECTR
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