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Application Notes: AN_SY8208A
High Efficiency Fast Response
8A Continuous, 16A Peak, 28V Input
Synchronous Step Down Regulator
General Description
The SY8208A develops a high efficiency synchronous
step-down DC-DC regulator capable of delivering 8A
continuous, 16A peak current. The SY8208A operates
over a wide input voltage range from 4V to 28V and
integrates main switch and synchronous switch with
very low RDS(ON) to minimize the conduction loss.
The SY8208A 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
800kHz under continuous conduction mode to
minimize the size of inductor and capacitor.
Ordering Information
SY8208 □(□□)□
Temperature Code
Package Code
Optional Spec Code
Temperature Range: -40°C to 85°C
Ordering Number Package type Note
SY8208AQNC QFN3x3-10
--
Typical Applications
Features
• Low RDS(ON) for internal switches (top/bottom):
20/10 mΩ
• Wide input voltage range: 4-28V
• Instant PWM architecture to achieve fast transient
responses
• Internal 400uS softstart limits the inrush current
• Pseudo-constant frequency: 800kHz.
• 8A continuous/16A peak output current capability
• ±1.5% 0.6V reference
• Programmable peak current limit
• Power good indicator
• Output discharge function
• Short circuit latch off protection
• Over voltage latch off protection
• Input UVLO
• Over temperature protection
• RoHS Compliant and Halogen Free
• Compact package: QFN3x3-10
Applications
• LCD-TV/Net-TV/3DTV
• Set Top Box
• Notebook
• High Power AP
VIN
CIN
10uF
High/Floating/Low
ON/OFF
CVCC
2.2uF
IN
GND
ILMT
EN
VCC
PG
BS
LX
FB
PG (Open Drain Output)
CBS
100nF
L 1.5uH
C1
220pF
VOUT=3.3V
R1
100k
COUT
22uF×3
R2
22.1k
Figure 1 Schematic
Figure 2. Efficiency
AN_SY8208A
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AN_SY8208A
Typical Performance Characteristics
Efficiency vs. Load Current
100
90
80
70
60
50
40
30
20
0.001
VIN=7.4V,VOUT=5.0V
VIN=12V,VOUT=5.0V
VIN=19V,VOUT=5.0V
VIN=28V,VOUT=5.0V
0.01 0.10
1.00
Load Current (A)
10.00
100
90
80
70
60
50
40
30
20
0.001
Efficiency vs. Load Current
VIN=5.0V,VOUT=3.3V
VIN=12V,VOUT=3.3V
VIN=19V,VOUT=3.3V
VIN=28V,VOUT=3.3V
0.01 0.10
1.00
Load Current (A)
10.00
95
85
75
65
55
45
35
25
15
0.001
Efficiency vs. Load Current
VIN=5.0V,VOUT=1.8V
VIN=12V,VOUT=1.8V
VIN=19V,VOUT=1.8V
VIN=28V,VOUT=1.8V
0.01 0.10
1.00
Load Current (A)
10.00
Load Transient
(VIN=12V, VOUT=5V, ILOAD=0.8-8A)
∆VOUT
100mV/div
IL 5A/div
95
85
75
65
55
45
35
25
15
0.001
Efficiency vs. Load Current
VIN=5.0V,VOUT=1.2V
VIN=12V,VOUT=1.2V
VIN=19V,VOUT=1.2V
VIN=28V,VOUT=1.2V
0.01 0.10
1.00
Load Current (A)
10.00
Load Transient
(VIN=12V, VOUT=5V, ILOAD=2-6A)
∆VOUT
100mV/div
IL 2A/div
Time (200µs/div)
Time (200µs/div)
AN_SY8208A
5