Applications Note: SY8087
High Efficiency 1.5MHz, 1.5A
Synchronous Step Down Regulator
General Description
The SY8087 is a high-efficiency, high frequency
synchronous step-down DC-DC regulator IC capable of
delivering up to 1.5A output currents. SY8087 operates
over a wide input voltage range from 3V to 5.5V and
integrates main switch and synchronous switch with
very low R
DS(ON)
to minimize the conduction loss.
Low output voltage ripple and small external inductor
and capacitor sizes are achieved with greater than
1MHz switching frequency.
Features
•
Low R
DS(ON)
for internal switches (top/bottom)
180m
Ω
/120m
Ω
•
3-5.5V input voltage range
•
High switching frequency 1.5MHz minimizes the
external components
•
Internal softstart limits the inrush current
•
100% dropout operation
•
RoHS Compliant and Halogen Free
•
Compact package: SOT23-5
Ordering Information
SY8087
□
(
□□
)
□
Temperature Code
Package Code
Optional Spec Code
Co
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ON/ OFF
p.
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Typical Applications
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Ordering Number
SY8087AAC
Package type
SOT23-5
Note
①
1.5A
EN
IN
LX
Co
r
V
IN
l-P
L
V
OUT
R
1
C
1
(opt.)
C
OUT
R
2
FB
•
•
•
•
•
C
IN
GND
Sil
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Figure 1.Schematic diagram
AN_SY8087 Rev. 1.0
Silergy Corp. Confidential- Prepared for Customer Use Only
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Set Top Box
Net PC
Mini-Notebook PC
Access Point Router
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Applications
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AN_SY8087
Pinout (top view)
SOT23-5
Top Mark: HLxyz (device
code: HL,
x=year code, y=week code, z= lot number code)
Pin Name
EN
GND
LX
IN
FB
Pin Number
1
2
3
4
6
Pin Description
Enable control. Pull high to turn on. Do not float.
Ground pin
Inductor pin. Connect this pin to the switching node of inductor.
Power input pin.
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:
Vout=0.6*(1+R
1
/R
2
).
Supply Input Voltage --------------------------------------------------------------------------------------------3V to 5.5V
Junction Temperature Range -----------------------------------------------------------------------------
-
40°C to 125°C
Ambient Temperature Range ------------------------------------------------------------------------------
-
40°C to 85°C
AN_SY8087 Rev. 1.0
Sil
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Recommended Operating Conditions
(Note 3)
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Co
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Supply Input Voltage -------------------------------------------------------------------------------------------------- 6.0V
Enable, FB Voltage--------------------------------------------------------------------------------------------- V
IN
+ 0.6V
Power Dissipation, P
D
@ T
A
= 25°C,
SOT23-5------------------------------------------------------------------------------------------------------ 0.6W
Package Thermal Resistance (Note 2)
SOT23-5,
θ
JA
------------------------------------------------------------------------------------------- 170°C/W
SOT23-5,
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
ESD Susceptibility (Note 2)
HBM (Human Body Mode) -------------------------------------------------------------------------------------------- 2kV
MM (Machine Mode) -------------------------------------------------------------------------------------------------- 200V
Dynamic LX voltage in 50ns duration -------------------------------------------------------------- IN+3V to GND-4V
p.
Co
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Silergy Corp. Confidential- Prepared for Customer Use Only
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l-P
Absolute Maximum Ratings
(Note 1)
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2
AN_SY8087
Function Block
IN
Internal
Power
Input UVLO
2.7V
Current Sense
EN
1.5V
PWM Control
& Protect Logic
LX
0.6V
re
Thermal
Protection
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p.
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Silergy Corp. Confidential- Prepared for Customer Use Only
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Co
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l-P
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GND
FB
AN_SY8087 Rev. 1.0
Sil
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3
AN_SY8087
Electrical Characteristics
(V
IN
= 5V, V
OUT
= 2.5V, L = 2.2uH, C
OUT
= 10uF, T
A
= 25°C, unless otherwise specified)
Note 3:
The device is not guaranteed to function outside its operating conditions.
AN_SY8087 Rev. 1.0
Sil
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Note 2:
θ
JA is measured in the natural convection at TA = 25°C on a low effective single layer thermal conductivity
test board of JEDEC 51-3 thermal measurement standard. Pin 2 of SOT23-5 packages is the case position for
θ
JC
measurement. Test condition: Device mounted on 2” x 2” FR-4 substrate PCB, 2oz copper, with minimum
recommended pad on top layer and thermal vias to bottom layer ground plane
Silergy Corp. Confidential- Prepared for Customer Use Only
fid
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Note 1:
Stresses listed as the above “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.
l-P
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Parameter
Input Voltage Range
Quiescent Current
Shutdown Current
Feedback Reference Voltage
FB Input Current
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
Thermal Shutdown
Temperature
T
SD
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fo
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Symbol
V
IN
I
Q
I
SHDN
V
REF
I
FB
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
V
FB
=V
IN
Min
3
70
0.588
-50
Typ
80
0.1
0.6
180
120
Max
5.5
100
1
0.612
50
200
160
1.8
1.5
0.4
2.7
1.3
0.1
1.5
50
160
2.0
100
Unit
V
µA
µA
V
nA
mΩ
mΩ
A
V
V
V
V
MHz
ns
%
°C
4
AN_SY8087
Typical Performance Characteristics
Efficiency vs. Load Current
95
100
Efficiency vs. Load Current
90
95
85
90
80
V
IN
=3.3V,V
OUT
=1.2V
75
70
10
100
1000
10000
V
IN
=4.2V,V
OUT
=1.2V
V
IN
=5.0V,V
OUT
=1.2V
85
V
IN
=3.3V,V
OUT
=1.8V
80
V
IN
=4.2V,V
OUT
=1.8V
V
IN
=5.0V,V
OUT
=1.8V
75
10
100
1000
10000
Load Current (mA)
Efficiency vs. Load Current
98
96
94
92
90
88
86
84
82
10
100
1000
V
IN
=4.2V,V
OUT
=3.3V
V
IN
=5.0V,V
OUT
=3.3V
Load Current (mA)
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10000
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I
L
(V
IN
=5.0V, V
OUT
=1.8V, I
LOAD
=0.15A)
∆Vout(AC) 10mV/div
r
V
LX
V
LX
I
L
Output Ripple
2V/div
200mA/div
Load Current (mA)
Output Ripple
Time (400ns/div)
Output Ripple
(V
IN
=5.0V, V
OUT
=1.8V, I
LOAD
=1.5A)
∆Vout(AC) 10mV/div
(V
IN
=5.0V, V
OUT
=1.8V, I
LOAD
=0.75A)
∆Vout(AC) 10mV/div
Co
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p.
Co
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2V/div
er
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V
LX
2V/div
I
L
500mA/div
1A/div
Sil
Time (400ns/div)
Time (400ns/div)
AN_SY8087 Rev. 1.0
Silergy Corp. Confidential- Prepared for Customer Use Only
5
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