SX2106
85T
21V, 2 A, 600KHz Synchronous Step- Down DC/DC Converter
85T
Description
The SX2106 is a synchronous step -down DC/DC
converter that provides wide 4.5V to 21V input
voltage range and 2A continuous load current
capability.
The SX2106 fault protection includes cycle -by-cycle
current limit, UVLO, output overvoltage protection
and thermal shutdown. The adjustable soft-start
function prevents inrush current at turn-on. This
device uses current mode control scheme which
provides
fast
transient
response.
Internal
Compensation
function
reduces
external
compensation components and simplifies the design
process. In shutdown mode, the supply current is
less than 1μA.
The SX2106 is available in a
SOT-23-6
package,
provides good thermal conductance.
Features
● High Efficiency up to 94%
● Low Rds(on) Integrated Power MOSFET
● Internal Compensation Function
● Wide Input Voltage Range: 4.5V to 21V
● Adjustable Output Voltage from 0.8V to 17.85V
● 2A Output Current
● Fixed 600KHz Switching Frequency
● Current Mode Operation
● Cycle-by-Cycle Current Limit
● Over-Temperature Protection with Auto Recovery
● Output Overvoltage Protection
● Under Voltage Lockout
● <1μA Shutdown Current
●
SOT-23-6
Package
Applications
● STB (Set-Top-Box)
● LCD Displays, TVs
● Distributed Power Systems
● Networking, XDSL Modems
Pin Assignments
S6 Package (SOT-23-6)
LX VIN SHDN
Ordering Information
SX2106
□□□
TR: Tape / Reel
C: Green
6
1
4
5
(Marking)
2
3
Package Type
S6: SOT-23-6
BST GND FB
Fig
ure 1. Pin Assignment of SX2106
Copyright ©2010 by Suosemi Corporation
1
SX2106
Typical Application Circuit
R3
100kΩ
C3
0.1μF
85T
4
SHDN
VIN
4.5V to 21V
C1
10μF/25V
CERAMIC x 2
1
BST
LX 6
L1
4.7μH
VOUT
3.3V
R1
30.9kΩ 1%
C4
(optional)
5
VIN
SX2106
FB
GND
2
3
C2
22μF/6.3V
CERAMIC x 2
R2
9.76kΩ 1%
Figure 2. C
IN
/C
OUT
use Ceramic Capacitors Application Circuit
C3
0.1μF
R1
V
OUT
½
0.805
1
V
R2
R3
100kΩ
4
SHDN
VIN
4.5V to 21V
C1
100μF/25V
EC x 1
C4
0.1μF/25V
CERAMIC x 1
1
BST
LX
6
L1
4.7μH
VOUT
3.3V
R1
30.9kΩ 1%
C2
100μF/6.3V
EC x 1
5
VIN
SX2106
FB
GND
2
3
R2
9.76kΩ 1%
Figure 3. C
IN
/C
OUT
use Electrolytic Capacitors Application Circuit
V
OUT
1.2V
1.8V
2.5V
3.3V
5V
1.2V
1.8V
2.5V
3.3V
5V
R1
4.99kΩ
4.99kΩ
4.99kΩ
30.9kΩ
30.9kΩ
4.99kΩ
4.99kΩ
4.99kΩ
30.9kΩ
30.9kΩ
R2
10kΩ
3.92kΩ
2.32kΩ
9.76kΩ
5.76kΩ
10kΩ
3.92kΩ
2.32kΩ
9.76kΩ
5.76kΩ
C4
10pF~1nF
10pF~1nF
10pF~1nF
10pF~1nF
10pF~1nF
--
--
--
--
--
L1
2.2μH
2.2μH
4.7μH
4.7μH
4.7μH
2.2μH
2.2μH
4.7μH
4.7μH
4.7μH
C
OUT
22μF MLCC x2
22μF MLCC x2
22μF MLCC x2
22μF MLCC x2
22μF MLCC x2
100μF EC x1
100μF EC x1
100μF EC x1
100μF EC x1
100μF EC x1
Table 1. Recommended Component Values
Copyright ©2010 by Suosemi Corporation
2
SX2106
Functional Pin Description
I/O
I
I
I
I
O
O
Pin Name
FB
VIN
SHDN
85T
Pin Function
Pin No.
3
5
4
2
6
1
Voltage Feedback Input Pin. Connect FB and V
OUT
with a resistive voltage
divider. This IC senses feedback voltage via FB and regulates it at 0.8V.
Power Supply Input Pin. Drive VIN pin by 4.5V to 21V voltage to power on
the chip.
Enable Input Pin. This pin is a digital control input that turns the converter on
or off. Connect to VIN with a 100KΩ resistor for self-startup.
Ground Pin.
Power Switching Output. LX is the output of the internal high side NMOS
switch.
High Side Gate Drive Boost Pin. A 10nF or greater capacitor must be
connected from this pin to LX. It can boost the gate drive to fully turn on the
internal high side NMOS.
GND
LX
BST
Block Diagram
VIN
SHDN
1M
UVLO
&
POR
ISEN
Internal
Regulator
VCC
OTP
VCC
OVP
Oscillator
BST
S
FB
Current
Comp
R
OTP
OVP
UVLO
PWM
Control
Driver
Logic
High-Side
MOSFET
LX
0.8V
Current
Limit
Low-Side
MOSFET
GND
Figure 4. Block Diagram of SX2106
Copyright ©2010 by Suosemi Corporation
3
SX2106
85T
Absolute Maximum Ratings
(Note 1)
● Supply Voltage V
IN
------------------------------------------------------------------------------------------- -0.3V to +23V
● Enable Voltage V
SHDN
-------------------------------------------------------------------------------------- -0.3V to +23V
● LX Voltage V
LX
(50ns) -------------------------------------------------------------------------------------- -1V to V
IN
+0.3V
● BST Pin Voltage V
BST
-------------------------------------------------------------------------------------- V
LX
-0.3V to V
LX
+6V
● All Other Pins Voltage ------------------------------------------------------------------------------------- -0.3V to +6V
● Maximum Junction Temperature (T
J
) ------------------------------------------------------------------ +150°C
● Storage Temperature (T
S
) -------------------------------------------------------------------------------- -65°C to +150°C
● Lead Temperature (Soldering, 10sec.) ---------------------------------------------------------------- +260°C
● Power Dissipation @T
A
=25°C, (P
D
)
SOT-23-6
-------------------------------------------------------------------------------------------- +0.40W
● Package Thermal Resistance, (θ
JA
):
SOT-23-6
-------------------------------------------------------------------------------------------- +250°C/W
● Package Thermal Resistance, (θ
JC
):
SOT-23-6
-------------------------------------------------------------------------------------------- +130°C/W
Note 1：Stresses beyond this listed under “Absolute Maximum Ratings" may cause permanent damage to the device.
Recommended Operating Conditions
● Supply Voltage V
IN
------------------------------------------------------------------------------------------- +4.5V to +21V
● Enable Voltage V
SHDN
-------------------------------------------------------------------------------------- 0V to V
IN
● Operation Temperature Range -------------------------------------------------------------------------- -40°C to +85°C
Copyright ©2010 by Suosemi Corporation
4
SX2106
Electrical Characteristics
(V
IN
=12V, T
A
=25
°C
, unless otherwise specified.)
Parameter
V
IN
Input Supply Voltage
V
IN
Quiescent Current
V
IN
Shutdown Supply Current
Feedback Voltage
Feedback OVP Threshold Voltage
High-Side MOSFET R
DS
(ON)
(Note 2)
Low-Side MOSFET R
DS
(ON)
(Note 2)
High-Side MOSFET Leakage
Current
High-Side MOSFET Current Limit
(Note 2)
Low-Side MOSFET Current Limit
(Note 2)
Error Amplifier Voltage Gain
(Note 2)
Oscillation frequency
Short Circuit Oscillation Frequency
Maximum Duty Cycle
Minimum On Time (Note 2)
Input UVLO Threshold
Under Voltage Lockout Threshold
Hysteresis
SHDN
Input Low Voltage
SHDN
Input High Voltage
SHDN
Input Current
85T
Conditions
Min
4.5
V
SHDN
=1.8V, V
FB
=1.0V
V
SHDN
=0V
4.5V≦V
IN
≦21V
0.779
0.8
1.4
120
110
V
SHDN
=0V, V
LX
=0V
Minimum Duty
From Drain to Source
2.5
3
10
2.5
1
0.821
Typ
Max
21
Unit
V
mA
μA
V
V
mΩ
mΩ
μA
A
A
V/V
720
KHz
KHz
%
ns
V
mV
0.4
2
V
IN
=2V
2
170
V
V
μA
°C
Symbol
V
IN
I
DDQ
I
SD
V
FB
V
OVP
R
DS(ON)
R
DS(ON)
I
LX(leak)
I
LIMIT(HS)
I
LIMIT(LS)
1.5
400
F
OSC
F
OSC(short)
D
MAX
T
MIN
V
UVLO(Vth)
V
UVLO(HYS)
V
SHDN
V
SHDN
(L)
480
V
FB
=0V
V
FB
=0.6V
600
140
90
100
V
IN
Rising
4.3
400
(H)
I
SHDN
T
SD
Thermal Shutdown Threshold
(Note 2)
Note 2：Not production tested.
Copyright ©2010 by Suosemi Corporation
5
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