ETC FR9702

FR9702
fitipower integrated technology lnc.
23V, 1.8A, 1.4MHz Asynchronous
Step-Down DC/DC Converter
Description
Features
The FR9702 is a monolithic step-down switch
mode converter with a built-in power MOSFET. It
achieves 1.8A output current over a wide input
supply range with excellent load and line
regulation. Current mode operation provides fast
transient response and eases loop stabilization.
Fault condition protection includes cycle-by-cycle
current limiting and over temperature protection.
The FR9702 requires a minimum number of
available standard external components. The
FR9702 is available in TSOT23-6 and SOT23-6
packages.
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Pin Assignment
TOP VIEW
BS 1
6 SW
GND 2
5 VIN
FB 3
4 EN
1.8A Output Current
180mΩ Internal Power MOSFET Switch
Stable with Low ESR Output Ceramic
Capacitors
Up to 92% Efficiency
Fixed 1.4MHz Frequency
Current Mode Operation
Over-Temperature Protection with
Hiccup-Mode
Cycle-by-Cycle Over Current Protection
Wide 4.5V to 23V Operating Input Range
Output Adjustable from 0.805V to 15V
10uA Shutdown Current
Available in TSOT23-6 and SOT23-6
Packages
Applications
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Distributed Power Systems
Battery Charger
OLPC, Netbook
Pre-Regulator for Linear Regulators
WLED Drivers
Ordering Information
FR9702□□□
TR: Tape / Reel
G: Green
Package Type
S6: SOT-23-6
FR9702-1.0-DEC-2009
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FR9702
fitipower integrated technology lnc.
Absolute Maximum Ratings (Note 1)
Supply Voltage VIN.....................................................................................26V
VSW...................................................................................–0.3V to VIN + 0.3V
VBS………………………………………………………………………...Vsw + 6V
All Other Pins………………………………………………………...–0.3V to +6V
Junction Temperature……………………………………………………….150°C
Lead Temperature .................................................................................260°C
Storage Temperature ...........................................................–65°C to +150°C
Recommended Operating Conditions (Note 2)
Input Supply Voltage VIN………………………………………………4.5V ~ 23V
Output Voltage VOUT.................................................................0.805V ~ 15V
Ambient Temperature TA……………………………………………-40°C ~ 85°C
Thermal Characteristics
TSOT23-6 θJA…………………………………………….………………220°C /W
TSOT23-6 θJC……………………………..………………….………..…110°C /W
SOT23-6 θJA……………………………………………………………...220°C /W
SOT23-6 θJC………………………………………………………………110°C /W
Note 1: Stresses exceed those ratings may damage the device.
Note 2: If out of its operation conditions, the device is not guaranteed to function.
Electrical Characteristic
( VIN = 12V, TA = 25℃, unless otherwise specified )
Parameter
Test Conditions
Min
Typ
Max
Unit
Feedback Voltage
Switch-On Resistance (*)
Switch Leakage
Current Limit (*)
Oscillator Frequency
Fold-back Frequency
Maximum Duty Cycle
Minimum On-Time (*)
4.5V ≤ VIN ≤ 23V
0.785
0.805
180
0.825
V
mΩ
μA
A
MHz
KHz
%
ns
FR9702-1.0-DEC-2009
VEN = 0V, VSW = 0V
10
1.2
VFB = 0V
3
1.4
460
85
100
1.7
2
FR9702
fitipower integrated technology lnc.
Electrical Characteristic (continued)
( VIN = 12V, TA = 25℃, unless otherwise specified )
Test Conditions
Parameter
Under Voltage Lockout Threshold Rising
Under Voltage Lockout Threshold
Hysteresis
EN Input Low Voltage
EN Input High Voltage
Min
Typ
Max
Unit
4.1
4.4
4.7
V
250
mV
0.4
V
V
1.2
Supply Current (Shutdown)
VEN = 2V
VEN = 0V
VEN = 0V
2.0
0.1
10
μA
Supply Current (Quiescent)
VEN = 2V, VFB = 1V
1.8
mA
150
°C
EN Input Current
Over-Temperature Protection Threshold (*)
μA
*: Guaranteed by design
Block Diagram
+
OVP
Oscillator
+
460KHz / 1.4MHz
-
BS
Error
Amplifier
S
SET
Q
Driver
R
CLR
High-Side
MOSFET
SW
Q
Current
Comparator
+
Ccomp
REGULATOR
-
1.2V
CLK
+
EN
6V
-
0.805V
+
+
0.45V
VIN
-
-
FB
Current Sense
Amplifier
+
0.9V
Internal
Compensation
Rcomp
RC
GND
OVP
OTP
VIN UVLO
950K
Figure 1
FR9702-1.0-DEC-2009
FR9702 Functional Block Diagram
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FR9702
fitipower integrated technology lnc.
Function Pin Description
Pin NO. Pin Name
Pin Description
Bootstrap. A 22nF capacitor is connected between SW and BS pins to drive the power
switch’s gate above the supply voltage.
Ground. This pin is the voltage reference for the regulated output voltage. For this reason
care must be taken in its layout.
Feedback. An external resistor divider from the output to GND, tapped to the FB pin sets
the output voltage.
1
BS
2
GND
3
FB
4
EN
On/Off Control Input. Pull EN above 1.2V and below 5V to turn the device on.
5
VIN
Power Supply Input. Drive 4.5V to 23V voltage to this pin to power on this chip.
Connecting a 10uF ceramic bypass capacitor between VIN and GND to eliminate noise.
6
SW
Switch Output. Connect this pin to the switching end of the inductor.
Typical Application Circuit
FR9702
Figure 2
FR9702-1.0-DEC-2009
Output 3.3V Application Circuit
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FR9702
fitipower integrated technology lnc.
Typical Operating Characteristics
VIN = 12V, VOUT = 3.3V, C1 = 10uF, C2 = 22uF, L1 = 4.7uH, TA = +25℃, unless otherwise noted.
Efficiency vs. Loading
Efficiency vs. Loading
100%
100%
90%
90%
80%
80%
VIN =12V
VIN =5V
60%
50%
40%
30%
VIN =23V
VIN =12V
70%
VIN =23V
Efficiency
Efficiency
70%
60%
50%
40%
30%
20%
20%
VOUT = 3.3V
10%
VOUT = 5V
10%
0%
0%
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
0
0.2
0.4
0.6
0.8
Load current (A)
1
1.2
1.4
1.6
1.8
Load current (A)
Feedback Voltage vs. Case Temperature
Switching Frequency vs. Case Temperature
IOUT = 0.2A
IOUT = 0.2A
0.816
1.6
0.814
1.55
Switching Frequency (MHz)
Feedback Voltage (V)
0.812
0.81
0.808
0.806
0.804
0.802
1.5
1.45
1.4
1.35
1.3
0.8
1.25
0.798
1.2
0.796
-40
-30
-20
-10
0
10
20
30
40
50
60
70
80
90
-40
100
-30
-20
-10
DC Ripple
Waveform
IOUT = 1.8A
VIN
50mV/div.
VIN
100mV/div.
VOUT
10mV/div.
VOUT
10mV/div.
IL
0.5A/div.
IL
0.5A/div.
VSW
5V/div.
VSW
5V/div.
400ns/div.
FR9702-1.0-DEC-2009
10
20
30
40
50
60
70
80
90
100
Case Temperature (℃)
Case Temperature (℃)
IOUT = 0.2A
0
DC Ripple
Waveform
400ns/div.
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FR9702
fitipower integrated technology lnc.
Typical Operating Characteristics (continued)
VIN = 12V, VOUT = 3.3V, C1 = 10uF, C2 = 22uF, L1 = 4.7uH, TA = +25℃, unless otherwise noted.
Startup Through
Enable Waveform
Startup Through
Enable Waveform
IOUT = 0.2A
IOUT = 1.8A
VEN
5V/div.
VEN
5V/div.
VOUT
1V/div.
IL
1A/div.
VOUT
1V/div.
IL
1A/div.
VSW
5V/div.
VSW
5V/div.
40us/div.
40us/div.
Shutdown Through
Enable Waveform
Shutdown Through
Enable Waveform
IOUT = 0.2A
IOUT = 1.8A
VEN
5V/div.
VEN
5V/div.
VOUT
1V/div.
VOUT
1V/div.
IL
1A/div.
IL
1A/div.
VSW
5V/div.
VSW
5V/div.
40us/div.
200us/div.
Load Transient
Waveform
Short Circuit Test
Waveform
IOUT = 200mA to 1.8A step
VOUT
1V/div.
VOUT
100mV/div.
IL
1A/div.
IL
1A/div.
400us/div.
FR9702-1.0-DEC-2009
20us/div.
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FR9702
fitipower integrated technology lnc.
Application Information
Setting EN Automatic Startup Voltage
FR9702
The external resistor divider is used
to set the EN automatic startup voltage:
R4 =
VEN
⎛ VIN-VEN ⎞
⎜ R3 ⎟
⎝
⎠
5V
≈ 71.5KΩ
⎛ 12V-5V ⎞
⎜ 100KΩ ⎟
⎝
⎠
Table 1 shows a list of resistor selection for
common input voltages:
Table 1—Resistor Selection for Common
Input Voltages
VIN
R3
R4
5V
100KΩ
NC
12V
100KΩ
71.5KΩ
16V
100KΩ
45.3KΩ
Setting Output Voltage
The external resistor divider is used to set the
output voltage. FR9702 feedback resistors are
unconcerned of compensation and provide an
easy way to program output voltage. Table 2
shows a list of resistor selection for common
output voltages:
⎛
⎝
VOUT = 0.805 × ⎜1+
FR9702-1.0-DEC-2009
R1 ⎞
⎟ V
R2 ⎠
VOUT
R1
R2
5V
43KΩ
8.2KΩ
3.3V
30.9KΩ
10KΩ
2.5V
21KΩ
10KΩ
1.8V
12.4KΩ
10KΩ
1.2V
4.99KΩ
10KΩ
Selecting the Inductor
For example, VIN = 12V, R3 = 100KΩ, thus R4
resistor value is:
R4 =
Table 2—Resistor Selection for Common
Output Voltages
A 4.7μH inductor with a DC current rating of at
least 25% percent higher than the maximum load
current is recommended for most applications.
For highest efficiency, the inductor’s DC
resistance should be less than 200mΩ. For most
designs, the required inductance value can be
derived from the following equation.
ΔI=0.3 × IL(MAX)
VOUT
⎛
⎞
L ≥ ( VIN-VOUT ) × ⎜
⎟
⎝ FSW × ΔI × VIN ⎠
Where ΔI is the inductor ripple current.
Choose the inductor ripple current to be 30% of
the maximum load current. The maximum
inductor peak current is calculated from:
IL(MAX) = ILOAD +
ΔIL
2
Under light load conditions below 100mA, a larger
inductance is recommended for improved
efficiency.
Selecting the Input Capacitor
The input capacitor reduces the surge current
drawn from the input supply and the switching
noise from the device. The input capacitor
impedance at the switching frequency should be
less than the input source impedance to prevent
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FR9702
fitipower integrated technology lnc.
recommended to follow these general guidelines
high frequency switching current from passing
through the input. Ceramic capacitors with X5R or
X7R dielectrics are highly recommended because
of their low ESR and small temperature
coefficients. For most applications, a 10μF
capacitor is sufficient.
show below:
1. Place the input capacitors, output capacitors
as close to the device as possible. Trace to
these capacitors should be as short and wide
as possible to minimize parasitic inductance
Selecting the Output Capacitor
and resistance.
The output capacitor keeps the output voltage
ripple small and a 22uF ceramic capacitor with
X5R or X7R dielectrics is recommended for its
low ESR characteristics.
2. Place VIN bypass capacitors close to the VIN
pin.
3. Place feedback resistors close to the FB pin.
4. Keep the sensitive signal FB away from the
switching signal SW.
External Bootstrap Diode
An external bootstrap diode is recommended if
the input voltage is less than 5V or if there is a 5V
system rail available. This diode helps improve
the efficiency. Low cost diodes, such as 1N4148
are suitable for this application.
FR9702
Figure 3
Recommended Layout Diagram
Rectifier Diode
Use a Schottky diode as the rectifier to conduct
current when the high-side power MOSFET is off.
The Schottky diode must have current rating
higher than the maximum output current and the
reverse voltage rating higher than the maximum
input voltage.
PCB Layout Recommendation
The
device’s
performance
and
stability
is
dramatically affected by PCB layout. It is
FR9702-1.0-DEC-2009
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FR9702
fitipower integrated technology lnc.
Package Information
SOT23-6
D
5
4
1
2
3
R
c
L2
e
e1
( TOP VIEW )
GAUGE PLANE
L
E
E1
L1
θ
6
( FRONT VIEW )
A
A2
θ2
UNIT: MM
y
A1
b
4×θ1
( SIDE VIEW )
1.2
2.6
0.6
0.95
( PCB FOOTPRINT )
SYMBOLS
A
A1
A2
b
c
D
E
E1
e
e1
L
L1
L2
y
R
θ
θ1
θ2
MIN
1.05
0.05
1.00
0.30
0.08
2.80
2.60
1.50
NOM
------1.10
------2.90
2.80
1.60
0.95 BSC
1.90 BSC
0.35
0.45
0.60 REF
0.25 BSC
------0.10
---0˚
---7˚ NOM
5˚ NOM
MAX
1.35
0.15
1.20
0.50
0.20
3.00
3.00
1.70
0.55
0.10
---8˚
NOTES:
1. JEDEC OUTLINE: MO-178C
2. DIMENSION “D” DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.MOLD
FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED .10mm PER SIDE.
3. DIMENSION “E1” DOES NOT INCLUDE INTER-LEAD FLASH, OR PROTRUSIONS. INTER-LEAD
FLASH OR PROTRUSIONS SHALL NOT EXCEED .15mm PER SIDE
FR9702-1.0-DEC-2009
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FR9702
fitipower integrated technology lnc.
Carrier Tape & Reel Dimensions
SOT23-6
9.20±0.10
76.2(3.0 INCHES)NOMINAL INSIDE
CORE DIAMETER
0.048±0.005
HEAT SEALABLE
ADHESIVE THIS SIDE
Φ1.5+0.1/-0.0
4.00
Φ1.00 MIN
2.00±.05
4.00
0.25±.05
1.75 ± .10
B
B
A
3.50 ± .05
R 0.3 MAX
Bo
8.0 +0.3/-0.1
A
R 0.3 TYP
Ko
Ao
SECTION A - A
SECTION B - B
0.20 MAX.
Ao = 3.15
NOTES:
Bo = 3.20
Ko = 1.40 +0.10/-0
1. DIM IN MM.
2. 10 SPROCKET HOLE PITCH CUMULATIVE TOLERANCE ±0.2.
3. POCKET POSITION RELATIVE TO SPROCKET HOLE MEASURED AS TRUE POSITION OF POCKET,
NOT POCKET HOLE.
Life Support Policy
Fitipower’s products are not authorized for use as critical components in life support devices or other medical systems.
FR9702-1.0-DEC-2009
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