SM8103
High Efficiency, 3.0A, 18V Input
Synchronous Step Down Regulator
General Description
The SM8103 is a high efficiency, 500kHz
synchronous step-down DC/DC regulator capable of
delivering up to 3A load current. It can operate over a
wide input voltage range from 4.2V to 18V and
integrate main switch and synchronous switch with
very low R
DS(ON)
to minimize the conduction loss.
The SM8103 adopts the instant PWM architecture to
achieve fast transient responses for high step down
applications and high efficiency at light loads. In
addition, it operates at pseudo-constant frequency of
500kHz to minimize the size of the inductor and the
capacitor.
Features
Ordering Information
SM8103
□
(
□□
)
□
Temperature Code
Package Code
Optional Spec Code
Low R
DS(ON)
for Internal Switches (Top/Bottom):
90mΩ/50mΩ
4.2-18V Input Voltage Range
3A Output Current Capability
500kHz Switching Frequency Minimize the
External Components
Stable with 10µF C
OUT
and 2.2µH Inductor
Instant PWM Architecture to Achieve Fast
Transient Responses
Internal Soft-start Limits the Inrush Current
Cycle-by-cycle Peak/Valley Current Limitation
Hic-cup Mode Output Short Circuit Protection
Thermal Shutdown with Auto Recovery
Output Auto Discharge Function
Compact Package: TSOT23-6
Applications
Set Top Box
Portable TV
DSL Modem
LCD TV
IP CAM
Networking
Ordering Number
SM8103ADC
Package type
TSOT23-6
Note
----
Typical Application
C
BS
100nF
Efficiency vs. Load Current
V
IN
:4.2~18V
BS
IN
LX
SM8103
C
IN
10uF
EN
GND
FB
R
H
100k
R
L
22.1k
C
FF
100pF
C
OUT
10uF
L 4.7uH
V
OUT
: 3.3V
100
95
90
Efficiency (%)
85
80
75
70
65
V
IN
=5V, V
OUT
=3.3V
V
IN
=12V, V
OUT
=3.3V
V
IN
=18V, V
OUT
=3.3V
0.1
1
10
Figure1. Schematic Diagram
Inductor and C
OUT
Selection Table
C
OUT
[µF]
L
[µH]
4.7
10
22
1.5
√
1.2
2.2
☆
2.2
√
√
3.3
4.7
☆
√
3.3
√
√
5
6.8
☆
√
Note:
‘☆’ means recommended for most applications.
V
OUT
[V]
60
0.01
Load Current (A)
Figure2. Efficiency vs. Output Current
AN_SM8103 Rev0.9A
© 2019 Silergy Corp.
Silergy Corp. Confidential- Prepared for Customer Use Only
1
All Rights Reserved.
SM8103
Pinout (top view)
BS
1
6
LX
GND 2
5
IN
FB
3
4
EN
TSOT23-6
Top mark:
J7xyz
(Device cod
e: J7
,
x=year code, y=week code, z= lot number code)
Pin Number
Pin Description
Boot-strap pin. Supply high side gate driver. Connect a 0.1µ ceramic capacitor
F
1
between BS and LX pins.
2
Power ground pin.
Output feedback pin. Connect this pin to the center point of the output resistor
3
divider (as shown in Figure 1) to program the output voltage:
V
OUT
=0.6×
(1+R
H
/R
L
).
4
Enable control. Pull high to turn on. Do not leave this pin floating.
5
6
Input pin. Decouple this pin to GND pin with at least a 10µF ceramic capacitor.
Inductor pin. Connect this pin to the switching node of inductor.
Pin Name
BS
GND
FB
EN
IN
LX
Block Diagram
IN
Current Sense
Internal
Power
Input
UVLO
4.15V
PWM
Control &
Protect
Logic
BS
LX
EN
1.2V
FB
0.6V
Internal
SST
Thermal
Protection
Current Sense
GND
Figure3. Block Diagram
AN_SM8103 Rev0.9A
© 2019 Silergy Corp.
Silergy Corp. Confidential- Prepared for Customer Use Only
2
All Rights Reserved.
SM8103
Absolute Maximum Ratings
(Note 1)
Supply Input Voltage ------------------------------------------------------------------------------------------------ -0.3V to 19V
LX, EN Voltage----------------------------------------------------------------------------------------------- -0.3V to V
IN
+ 0.3V
FB, BS-LX Voltage---------------------------------------------------------------------------------------------------- -0.3V to 4V
Power Dissipation, P
D
@ T
A
= 25° TSOT23-6, ----------------------------------------------------------------------- 1.5W
C
Package Thermal Resistance (Note 2)
θ
JA
---------------------------------------------------------------------------------------------------------------- 66°
C/W
θ
JC
---------------------------------------------------------------------------------------------------------------- 15°
C/W
Junction Temperature Range ------------------------------------------------------------------------------------ -40° to 150°
C
C
Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------------ 260°
C
Storage Temperature Range -------------------------------------------------------------------------------------- -65° to 150°
C
C
Dynamic LX Voltage in 10ns Duration (Note3) ---------------------------------------------------------- IN+3V to GND-5V
Recommended Operating Conditions
(Note 3)
Supply Input Voltage -------------------------------------------------------------------------------------------------- 4.2V to 18V
Junction Temperature Range ------------------------------------------------------------------------------------- -40° to 125°
C
C
Ambient Temperature Range --------------------------------------------------------------------------------------
-
40° to 85°
C
C
AN_SM8103 Rev0.9A
© 2019 Silergy Corp.
Silergy Corp. Confidential- Prepared for Customer Use Only
3
All Rights Reserved.
SM8103
Electrical Characteristics
(V
IN
= 12V, V
OUT
= 3.3V, L = 4.7µH, C
OUT
= 10µ T
A
= 25° I
OUT
= 1A unless otherwise specified)
F,
C,
Parameter
Input Voltage Range
Input UVLO Threshold
Input UVLO Hysteresis
Quiescent Current
Shutdown Current
Feedback Reference Voltage
FB Input Current
Output Discharge Resistance
Top FET R
ON
Bottom FET R
ON
EN Rising Threshold
EN Falling Threshold
Min ON Time
Min OFF Time
Turn On Delay
Soft-start Time
Switching Frequency
Top FET Current Limit
Bottom FET Current Limit
Output Under Voltage
Protection Threshold
Output UVP Delay
UVP Hiccup ON Time
UVP Hiccup OFF Time
Thermal Shutdown
Temperature
Thermal Shutdown
Hysteresis
Symbol
V
IN
V
UVLO
V
HYS
I
Q
I
SHDN
V
REF
I
FB
R
DIS
R
DS(ON)1
R
DS(ON)2
V
EN,R
V
EN,F
t
ON,MIN
t
OFF,MIN
t
ON,DLY
t
SS
F
SW
I
LIM,TOP
I
LIM,BOT
V
UVP
t
UVP,DLY
t
UVP,ON
t
UVP,OFF
T
SD
T
HYS
Test Conditions
Min
4.2
Typ
Max
18
4.15
Unit
V
V
V
µA
µA
mV
nA
Ω
mΩ
mΩ
V
V
ns
ns
µs
1.5
ms
kHz
A
A
33%
100
2
6
150
15
V
REF
µs
ms
ms
˚C
˚C
I
OUT
=0, V
FB
=V
REF
×
105%
EN=0
V
FB
=3.3V
588
-50
0.3
250
5
600
40
90
50
1.2
1.0
50
200
300
10
612
50
1.08
0.9
1.32
1.1
from EN high to LX start
switching
V
OUT
from 0 to 100%
V
OUT
=3.3V, CCM
0.5
4.5
3
1
500
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.
C
Note 2:
θ
JA
is measured in the natural convection at T
A
= 25° on a 2OZ two-layer Silergy evaluation board.
Paddle of TSOT23-6 package is the case position for SM8103
θ
JC
measurement.
Note 3:
The device is not guaranteed to function outside its operating conditions.
AN_SM8103 Rev0.9A
© 2019 Silergy Corp.
Silergy Corp. Confidential- Prepared for Customer Use Only
4
All Rights Reserved.
SM8103
Typical Performance Characteristics
Efficiency vs. Load Current
100
95
90
100
95
90
Efficiency vs. Load Current
Efficiency (%)
85
80
75
70
65
60
0.01
0.1
1
10
V
IN
=5V, V
OUT
=1.2V
V
IN
=12V, V
OUT
=1.2V
V
IN
=18V, V
OUT
=1.2V
Efficiency (%)
85
80
75
70
65
60
0.01
0.1
1
10
V
IN
=5V, V
OUT
=1.8V
V
IN
=12V, V
OUT
=1.8V
V
IN
=18V, V
OUT
=1.8V
Load Current (A)
Load Current (A)
Efficiency vs. Load Current
100
95
90
Efficiency vs. Load Current
100
95
90
Efficiency (%)
Efficiency (%)
V
IN
=5V, V
OUT
=3.3V
V
IN
=12V, V
OUT
=3.3V
V
IN
=18V, V
OUT
=3.3V
0.1
1
10
85
80
75
70
65
60
0.01
85
80
75
70
65
60
0.01
0.1
1
10
V
IN
=7.4V,V
OUT
=5V
V
IN
=12V,V
OUT
=5V
V
IN
=18V,V
OUT
=5V
Load Current (A)
Load Current (A)
Output Ripple
(V
IN
=12V, V
OUT
=3.3V, I
LOAD
=0A)
Output Ripple
(V
IN
=12V, V
OUT
=3.3V, I
LOAD
=3A)
∆V
OUT
200mV/div
∆V
OUT
100mV/div
V
LX
5V/div
V
LX
5V/div
I
L
I
L
1A/div
2A/div
Time (2μs/div)
Time (2μs/div)
AN_SM8103 Rev0.9A
© 2019 Silergy Corp.
Silergy Corp. Confidential- Prepared for Customer Use Only
5
All Rights Reserved.
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