Application Note: SM8082A
High Efficiency, 1.5MHz, 2A
Synchronous Step Down Regulator
`
General Description
The SM8082A is a high efficiency 1.5MHz
synchronous step down DC/DC regulator, which is
capable of delivering up to 2A output current. It can
operate over a wide input voltage range from 2.5V to
5.5V and integrate main switch and synchronous
switch with very low R
DS(ON)
to minimize the
conduction loss.
The low output voltage ripple, the small external
inductor and the capacitor sizes are achieved with
1.5MHz switching frequency.
Features
2.5V to 5.5V Input Voltage Range
70μA Low Quiescent Current
Low R
DS(ON)
for Internal Switches (Top/Bottom)
130mΩ /90mΩ
High Switching Frequency 1.5MHz Minimizes
the External Components
Internal Soft-start Limits the Inrush Current
100% Dropout Operation
Hic-cup for Short Circuit Protection
Output Auto Discharge Function
RoHS Compliant and Halogen Free
Compact Package: SOT23-5
Ordering Information
SM8082
□
(
□□
)
□
Temperature Code
Package Code
Optional Spec Code
Applications
Note
--
Set Top Box
USB Dongle
Media Player
Smart phone
Ordering Number
SM8082AAAC
Package type
SOT23-5
Typical Applications
V
IN
: 2.5-5.5V
C
IN
10μF/6.3V
EN
GND
FB
L
1
:1.0µH
IN
LX
R
H
100k
R
L
49.9k
C
ff
22pF
Efficiency vs. Output Current
V
OUT
:1.8V
100
C
OUT
10μF/10V
95
Efficiency (%)
90
85
Figure1. Schematic Diagram
Inductor and C
OUT
Selection Table
V
OUT
[V]
1.2/ 1.8
/3.3
L [µH]
0.47
1.0
2.2
4.7
C
OUT
[µF]
10
22
√
☆
√
√
√
2×
22
√
√
√
80
V
IN
=3.3V, V
OUT
=1.8V
V
IN
=4.2V, V
OUT
=1.8V
V
IN
=5.0V, V
OUT
=1.8V
0.01
0.1
1
10
75
70
0.001
Note:
‘☆’ means recommended for most applications.
Output Current (A)
Figure2. Efficiency vs. Output Current
AN_SM8082A Rev. 0.0
© 2019 Silergy Corp.
Silergy Corp. Confidential- Prepared for Customer Use Only
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All Rights Reserved.
SM8082A
Pinout (Top View)
EN 1
GND 2
LX
3
(SOT23-5)
5
FB
4
IN
Top Mark:K6xyz
(device
code: K6,
x=year code, y=week code, z= lot number code)
Pin Name
EN
GND
LX
IN
FB
Pin Number
1
2
3
4
5
Pin Description
Enable control. Pull high to turn on. Do not leave it floating.
Ground pin.
Inductor pin. Connect this pin to the switching node of the inductor.
Input pin. Decouple this pin to the GND pin with at least a 10µ ceramic capacitor.
F
Output feedback pin. Connect this pin to the center point of the output resistor divider
(as shown in Figure 1) to program the output voltage: V
OUT
=0.6×
(1+R
H
/R
L
).
Block Diagram
IN
Current
Sense
Internal
Power
Input
UVLO
EN
1.2V
0.6V
FB
120%V
REF
OVP
Control
Logic
LX
GND
Soft
Start
Thermal
Detect
Figure3. Block Diagram
AN_SM8082A Rev. 0.0
© 2019 Silergy Corp.
Silergy Corp. Confidential- Prepared for Customer Use Only
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All Rights Reserved.
AN_SM8082A
Absolute Maximum Ratings
(Note 1)
Supply Input Voltage ---------------------------------------------------------------------------------------------- -0.3V to 6.0V
FB, EN Voltage------------------------------------------------------------------------------------------- -0.3V to V
IN
+0.6V
LX Voltage------------------------------------------------------------------------------------------------------- -0.3V
(*1)
to 6.0V
(*2)
Power Dissipation, P
D
@ T
A
= 25° -------------------------------------------------------------------------------0.83W
C
Package Thermal Resistance (Note 2)
θ
JA
-------------------------------------------------------------------------------------------- ----------120°
C/W
θ
JC
----------------------------------------------------------------------------------------------- --------------20°
C/W
o
Junction Temperature Range ------------------------------------------------------------------------------------- -40 C to 150°
C
Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------------ 260°
C
Storage Temperature Range --------------------------------------------------------------------------------------
-
65° to 150°
C
C
(*1)
LX Voltage Tested Down to -3V<40ns
(*2)
LX Voltage Tested Up to +7V<40ns
Recommended Operating Conditions
(Note 3)
Supply Input Voltage ------------------------------------------------------------------------------------------------- 2.5V to 5.5V
Junction Temperature Range ------------------------------------------------------------------------------------- -40° to 125°
C
C
Ambient Temperature Range --------------------------------------------------------------------------------------- -40° to 85°
C
C
AN_SM8082A Rev. 0.0
© 2019 Silergy Corp.
Silergy Corp. Confidential- Prepared for Customer Use Only
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All Rights Reserved.
AN_SM8082A
Electrical Characteristics
(V
IN
= 5V, V
OUT
= 1.8V, L = 1.0μH, C
OUT
= 10μF, T
A
= 25° unless otherwise specified)
C,
Parameter
Symbol Test Conditions
Min
Input Voltage Range
V
IN
2.5
Input UVLO Threshold
V
UVLO
Input UVLO Hysteresis
V
HYS
Quiescent Current
I
Q
V
FB
=V
REF
×
105%
Shutdown Current
I
SHDN
V
EN
=0V
Feedback Reference Voltage
V
REF
I
OUT
=0.5A, CCM
588
LX Node Discharge Resistance
R
DIS
Top FET R
ON
R
DS(ON)1
Bottom FET R
ON
R
DS(ON)2
EN Input Voltage High
V
EN,H
1.2
EN Input Voltage Low
V
EN,L
Min on Time
t
ON,MIN
Maximum Duty Cycle
D
MAX
100
Turn on Delay
t
ON,DLY
from EN high to LX start switching
Soft-start Time
t
SS
V
OUT
from 0% to 100%
Switching Frequency
f
SW
I
OUT
=0.5A, CCM
Top FET Current Limit
I
LMT,TOP
3.5
Thermal Shutdown Temperature
T
SD
Thermal Shutdown Hysteresis
T
HYS
Typ
Max
5.5
2.5
100
1
612
Unit
V
V
mV
µA
µA
mV
Ω
mΩ
mΩ
V
V
ns
%
ms
ms
MHz
A
°
C
°
C
150
70
0.1
600
50
130
90
0.4
60
0.5
1
1.5
150
20
Note 1:
Stresses beyond the “Absolute Maximum Ratings” may cause permanent damage to the device. These are
stress ratings only. Functional operation of the device at these or any other conditions beyond those indicated in the
operational sections of the specification is not implied. Exposure to absolute maximum rating conditions for
extended periods may affect device reliability.
Note 2:
Ѳ
JA
of SM8082A is measured in the natural convection at T
A
= 25
o
C on a 2OZ two-layer Silergy evaluation
board. Pin 3 is the case position for Ѳ
JC
measurement.
Note 3:
The device is not guaranteed to function outside its operating conditions.
AN_SM8082A Rev. 0.0
© 2019 Silergy Corp.
Silergy Corp. Confidential- Prepared for Customer Use Only
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All Rights Reserved.
AN_SM8082A
Typical Performance Characteristics
Efficiency vs. Output Current
95
100
Efficiency vs. Output Current
95
90
Efficiency (%)
V
IN
=3.3V,V
OUT
=1.2V
V
IN
=4.2V, V
OUT
=1.2V
V
IN
=5.0V, V
OUT
=1.2V
Efficiency (%)
90
85
85
80
80
V
IN
=3.3V, V
OUT
=1.8V
V
IN
=4.2V, V
OUT
=1.8V
V
IN
=5.0V, V
OUT
=1.8V
0.01
0.1
1
10
75
75
70
0.001
0.01
0.1
1
10
70
0.001
Output Current (A)
Output Current (A)
Efficiency vs. Output Current
100
98
96
Output Ripple
(V
IN
=5.0V, V
OUT
=1.8V, I
OUT
=2.0A)
∆Vout
20mV/div
Efficiency (%)
94
92
90
88
86
84
82
80
0.001
V
IN
=4.2V, V
OUT
=3.3V
V
IN
=5.0V, V
OUT
=3.3V
V
LX
5V/div
I
L
2A/div
0.01
0.1
1
10
Output Current (A)
Time (2µs/div)
Startup from Enable
(V
IN
=5.0V, V
OUT
=1.8V, R
LOAD
=0.9Ω)
Shutdown from Enable
(V
IN
=5.0V, V
OUT
=1.8V, R
LOAD
=0.9Ω)
V
EN
V
OUT
5V/div
2V/div
V
EN
V
OUT
5V/div
2V/div
V
LX
5V/div
V
LX
5V/div
I
L
2A/div
I
L
2A/div
Time (800µs/div)
Time (800µs/div)
AN_SM8082A Rev. 0.0
© 2019 Silergy Corp.
Silergy Corp. Confidential- Prepared for Customer Use Only
5
All Rights Reserved.
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