Application Note: SY8079
High Efficiency 6.5V, 2A continuous, 3A peak, 1MHz
Synchronous Step Down Regulator
Preliminary Specification
General Description
The SY8079 is a high-efficiency, high frequency
synchronous step-down DC-DC regulator IC capable of
delivering up to 2A output current. The SY8079
operates over a wide input voltage range from 2.7V to
6.5V 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):125m
Ω
/95m
Ω
•
2.7-6.5V input voltage range
•
2A continuous, 3A peak load current capability
•
1MHz switching frequency minimizes the external
components
•
Internal softstart limits the inrush current
•
100% dropout operation
•
RoHS Compliant and Halogen Free
•
Compact package: SOT23-5
SY8079
□
(
□□
)
□
Temperature Code
Package Code
Optional Spec Code
Ordering Number
SY8079AAC
Package type
SOT23-5
Co
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Typical Applications
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•
•
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LCD TV
Set Top Box
Net PC
Mini-Notebook PC
Access Point Router
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92
88
84
80
0.01
Ordering Information
Applications
IN
C
IN
22µF
Co
r
p.
V
IN
: 2.7-6.5V
4
LX
3 L
1
:2.2µH
V
OUT
: 1.8V
R
1
200k
C
1
22pF
C
OUT
22µFх2
FB
ON/ OFF
gy
1
5
R
2
100k
V
IN
=3.3V,V
OUT
=1.8V
V
IN
=4.2V,V
OUT
=1.8V
V
IN
=5.0V,V
OUT
=1.8V
EN
GND
2
Sil
er
d
fo
Efficiency vs. Load Current
0.10
1.00
rs
ky
wo
Load Current (A)
Figure 1.Schematic diagram
Figure 2. Efficiency vs Load Current
AN_SY8079 Rev. 0.1
Silergy Corp. Confidential- Prepared for Customer Use Only 1
rth
10.00
SY8079
Pinout (top view)
(SOT23-5)
Top Mark: UHxyz
(device
code: UH,
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 inductor.
Input pin. Decouple this pin to GND pin with at least 10µF ceramic cap.
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 ------------------------------------------------------------------------------------------------ 2.7V to 6.5V
Enable, FB Voltage ------------------------------------------------------------------------------------------------------ V
IN
+0.3V
Junction Temperature Range ------------------------------------------------------------------------------------
-
40°C to 125°C
Ambient Temperature Range -------------------------------------------------------------------------------------
-
40°C to 85°C
AN_SY8079 Rev. 0.1
Sil
er
gy
Recommended Operating Conditions
(Note 3)
Co
r
Supply Input Voltage ----------------------------------------------------------------------------------------------- -0.3V to 7.0V
Enable, FB Voltage-------------------------------------------------------------------------------------------------- -0.3V to7.0V
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 ----------------------------------------- ------------------------------------------
-
40°C to 150°C
Lead Temperature (Soldering, 10 sec.) ----------------------------------------------------------------------------------- 260°C
Storage Temperature Range -------------------------------------------------------------------------------------
-
65°C to 150°C
p.
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Silergy Corp. Confidential- Prepared for Customer Use Only 2
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Absolute Maximum Ratings
(Note 1)
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SY8079
Block Diagram
AN_SY8079 Rev. 0.1
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Co
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Silergy Corp. Confidential- Prepared for Customer Use Only 3
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SY8079
Electrical Characteristics
(V
IN
= 5V, V
OUT
= 2.5V, L = 2.2µH, C
OUT
= 22µF, T
A
= 25°C, unless otherwise specified)
Note 3:
The device is not guaranteed to function outside its operating conditions.
AN_SY8079 Rev. 0.1
Sil
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p.
Note 2:
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.
Co
n
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.
Silergy Corp. Confidential- Prepared for Customer Use Only 4
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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
Short Circuit Protection Latch Off
Threshold
Min ON Time
Max Duty Cycle
Soft Start Time
Output Discharge Switch On
Resistance
Thermal Shutdown Temperature
re
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
V
SCP
Test Conditions
I
OUT
=0, V
FB
=V
REF
⋅
105%
EN=0
Min
2.7
Typ
55
0.1
0.6
125
95
Max
6.5
0.588
ky
0.2
1
0.3
75
1.0
50
150
3.5
1.5
d
I
OUT
=500mA
fo
rs
re
pa
100
wo
0.4
2.65
rth
1
0.612
Unit
V
µA
µA
V
mΩ
mΩ
A
V
V
V
V
MHz
V
ns
%
ms
Ω
°C
T
SD
l-P
T
SS
R
DISCH
SY8079
Typical Performance Characteristics
Efficiency vs. Load Current
95
96
Efficiency vs. Load Current
90
92
85
88
80
V
IN
=3.3V,V
OUT
=1.2V
V
IN
=4.2V,V
OUT
=1.2V
V
IN
=5.0V,V
OUT
=1.2V
84
V
IN
=3.3V,V
OUT
=1.8V
V
IN
=4.2V,V
OUT
=1.8V
V
IN
=5.0V,V
OUT
=1.8V
75
0.01
0.10
1.00
10.00
0.01
rs
0.10
70
80
ky
wo
1.00
10.00
0.2V/div
1A/div
Load Current (A)
Efficiency vs. Load Current
98
96
94
92
90
88
86
84
82
80
0.01
0.10
1.00
V
IN
=4.2V,V
OUT
=3.3V
V
IN
=5.0V,V
OUT
=3.3V
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10.00
d
Load Current (A)
AN_SY8079 Rev. 0.1
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Silergy Corp. Confidential- Prepared for Customer Use Only 5
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Load Current (A)
Load Transient
(V
IN
=5.0V, V
OUT
=1.8V, I
OUT
=0.2-2.0A)
V
OUT
I
L
Time (40µs/div)
rth
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