Application Notes: AN_SYH407
High Efficiency 1.5MHz, 1A
Synchronous Step Down Regulator
General Description
SYH407 is a high efficiency 1.5MHz synchronous step
down DC/DC regulator IC capable of delivering up to
1A output current. It can operate over a wide input
voltage range from 2.5V to 6.5V and integrate main
switch and synchronous switch with very low R
DS (ON)
to minimize the conduction loss.
Features
•
Low R
DS(ON)
for internal switches (top/bottom)
260mΩ/170mΩ
•
2.5~6.5V input voltage range
•
40µA typical quiescent current
•
High light load efficiency
•
High switching frequency 1.5MHz minimizes the
external components
•
Internal soft-start limits the inrush current
•
100% dropout operation
•
RoHS Compliant and Halogen Free
•
Compact package: SOT23-5
Ordering Information
SYH407
□
(□□
□
□□)□
□□
Tempera ture Code
Packa ge Code
Optiona l Spec Code
Temperature Range:
-
40°C to 85°C
Ordering Number
SYH407AAC
Package Type
SOT23-5
Note
1A
Applications
•
•
•
•
•
Portable Navigation Device
Set Top Box
USB Dongle
Media Player
Smart phone
Typical Application
Efficiency vs. Load Current
93
88
Efficiency (%)
83
78
Vin=6.5V Vout=1.8V
Vin=5.0V Vout=1.8V
73
Vin=4.2V Vout=1.8V
Vin=3.3V Vout=1.8V
68
1
10
100
1000
Load Current (mA)
Figure1. Schematic Diagram
Figure2. Efficiency
AN_SYH407 Rev. 0.9
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AN_SYH407
Pinout (Top View)
(SOT23-5)
Top Mark: TRxyz
(device
code: TR,
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 float.
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 10uF ceramic
capacitor.
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
1
/R
2
).Add optional C
1
(10pF~47pF) to speed up the transient
response.
Absolute Maximum Ratings
(Note 1)
Supply Input Voltage -------------------------------------------------------------------------------------------------------- 7.0V
Enable, FB Voltage---------------------------------------------------------------------------------------------------- V
IN
+ 0.6V
Power Dissipation, P
D
@ T
A
= 25°C, SOT23-5--------------------------------------------------------------------------- 0.6W
Package Thermal Resistance (Note 2)
θ
JA
-------------------------------------------------------------------------------------------------------------- 170°C/W
θ
JC
---------------------------------------------------------------------------------------------------------- ----130°C/W
Junction Temperature Range ----------------------------------------------------------------------------------------------125°C
Lead Temperature (Soldering, 10 sec.) ---------------------------------------------------------------------------------- 260°C
Storage Temperature Range -----------------------------------------------------------------------------------
-
65°C to 150°C
Recommended Operating Conditions
(Note 3)
Supply Input Voltage ----------------------------------------------------------------------------------------------- 2.5V to 6.5V
Junction Temperature Range -----------------------------------------------------------------------------------
-
40°C to 125°C
Ambient Temperature Range ------------------------------------------------------------------------------------
-
40°C to 85°C
AN_SYH407 Rev. 0.9
Silergy Corp. Confidential- Prepared for Customer Use Only
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AN_SYH407
Electrical Characteristics
(V
IN
= 5V, V
OUT
= 2.5V, L = 2.2uH, C
OUT
= 10uF, T
A
= 25°C, unless otherwise specified)
Parameter
Input Voltage Range
Quiescent Current
Shutdown Current
Feedback Reference Voltage
PFET RON
NFET RON
PFET Current Limit
EN rising threshold
EN falling threshold
Input UVLO threshold
UVLO hysteresis
Oscillator Frequency
Min ON Time
Max Duty Cycle
Soft Start Time
Thermal Shutdown Temperature
Thermal Shutdown Hysteresis
Symbol
V
IN
I
Q
I
SHDN
V
REF
R
DS(ON)
,
P
R
DS(ON)
,
N
I
LIM
V
ENH
V
ENL
V
UVLO
V
HYS
F
OSC
Test Conditions
I
OUT=
0
,
V
FB
=V
REF
⋅
105%
EN=0
Min
2.5
Typ
40
0.1
0.6
260
170
Max
6.5
1
0.612
0.588
Unit
V
µA
µA
V
mΩ
mΩ
A
V
V
V
V
MHz
ns
%
ms
°C
°C
1.3
1.5
0.4
2.5
0.1
1.5
80
100
1
150
15
T
SS
T
SD
T
HYS
Note 1:
Stresses beyond the “Absolute Maximum Ratings” may cause permanent damage to the device. These are
for stress ratings. Functional operation of the device at these or any other conditions beyond those indicated in the
operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for
extended periods may remain possibility to affect device reliability.
Note 2:
θ
JA is measured in the natural convection at T
A
= 25°C on a low effective single layer thermal conductivity
test board of JEDEC 51-3 thermal measurement standard. Exposed Paddle of DFN package is the case position for
θ
JC measurement.
Note 3:
The device is not guaranteed to function outside its operating conditions.
AN_SYH407 Rev. 0.9
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AN_SYH407
Typical Performance Characteristics
Efficiency vs. Load Current
90
93
Efficiency vs. Load Current
85
88
80
83
75
Vin=6.5V Vout=1.2V
Vin=5.0V Vout=1.2V
65
Vin=4.2V Vout=1.2V
Vin=3.3V Vout=1.2V
60
1
10
100
1000
68
1
10
100
1000
73
78
Vin=6.5V Vout=1.8V
Vin=5.0V Vout=1.8V
Vin=4.2V Vout=1.8V
Vin=3.3V Vout=1.8V
70
Load Current (mA)
Efficiency vs. Load Current
98
95
92
89
86
83
80
77
74
71
1
10
100
1000
Vin=6.5V Vout=3.3V
Vin=5.0V Vout=3.3V
Vin=4.2V Vout=3.3V
I
L
L
X
∆Vout
Load Current (mA)
Output Ripple
(V
IN
=5.0V, V
OUT
=1.8V, I
LOAD
=0A)
10mV/div
2.0V/div
0.2A/div
Time (400ns/div)
Load Current (mA)
Output Ripple
(V
IN
=5.0V, V
OUT
=1.8V, I
LOAD
=1.0A)
∆Vout
10mV/div
L
X
2.0V/div
I
L
1A/div
Time (400ns/div)
AN_SYH407 Rev. 0.9
Silergy Corp. Confidential- Prepared for Customer Use Only
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AN_SYH407
Startup from Enable
(V
IN
=5.0V, V
OUT
=1.8V, I
LOAD
=1.0A)
Shutdown from Enable
(V
IN
=5.0V, V
OUT
=1.8V, I
LOAD
=1.0A)
EN
5.0V/div
EN
5.0V/div
V
OUT
1.0V/div
L
X
5.0V/div
I
L
1.0A/div
Time (400µs/div)
Time (40µs/div)
AN_SYH407 Rev. 0.9
Silergy Corp. Confidential- Prepared for Customer Use Only
5
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