RT9276 - Farnell

®
RT9276
Synchronous Boost Converter with Voltage Detector
General Description
Features
The RT9276 is a synchronous boost converter, which is
based on a fixed frequency Pulse-Width-Modulation
(PWM) controller using a synchronous rectifier to obtain
maximum efficiency. The converter provides a power
supply solution for products powered by a variety of
batteries such as single cell, dual cell alkaline, NiMH and
NiCd battery. At light load currents, the converter enters
power save mode to maintain a high efficiency over a wide
load current range.
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True Load Disconnection During Shutdown
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Internal Synchronous Rectifier
Up to 96% Efficiency
Current Mode PWM Operation with Internal
Compensation
Low Start-Up Voltage
Low Quiescent Current
Internal Soft-Start Control
Low Battery Comparator
Low EMI Converter (Anti-Ringing)
Power Save Mode for Improved Efficiency at Light
Load Current
Over Current Protection
Short Circuit Protection
Over Temperature Protection
Over Voltage Protection
Small WDFN-10L 3x3 Package
RoHS Compliant and Halogen Free
The output voltage can be programmed by an external
resistor divider, or fixed at a certain voltage. Moreover, the
converter can be disabled to minimize battery drain. During
shutdown, the load is completely disconnected from the
battery. The maximum peak current in the boost switch
is limited to 2A for current limit.
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For the RT9276, a low-EMI mode is implemented to reduce
ringing of the inductor phase pin when the converter enters
discontinuous conduction mode. Moreover, a voltage
detector is built-in in the chip for low battery detection.
Ordering Information
)
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Applications
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All One-Cell, Two-Cell and Three-Cell Alkaline, NiCd,
NiMH and Single-Cell Li Batteries
Hand-Held Devices
WLED Flash Light
Package Type
QW : WDFN-10L 3x3 (W-Type)
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Lead Plating System
G : Green (Halogen Free and Pb Free)
Pin Configurations
(TOP VIEW)
Boost VOUT
Default : Adjustable
33 : 3.3V
50 : 5.0V
EN
VOUT
FB/NC
LBO
GND
1
2
3
4
5
GND
RT9276(-
z
11
10
9
8
7
6
PGND
LX
PGOOD
LBI
VBAT
Note :
WDFN-10L 3x3
Richtek products are :
`
RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020.
`
Marking Information
EW= : Product Code
Suitable for use in SnPb or Pb-free soldering processes.
EW=YM
DNN
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DS9276-02 July 2013
YMDNN : Date Code
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1
RT9276
Typical Application Circuit
L
VBAT
CIN
RT9276
2
9 LX
VOUT
6 VBAT
VOUT
R3
COUT
FB 3
R1
7
R2
10 PGND
Chip Enable
R5
R6
R4
LBI
LBO 4
8
PGOOD
1 EN
GND
LBO
PGOOD
5, Exposed Pad (11)
Figure 1. Adjustable Output Voltage Boost Converter with Voltage Detector
L
VBAT
CIN
RT9276
2
9 LX
VOUT
6 VBAT
7
Chip Enable
R3
COUT
LBO 4
R1
R2
VOUT
R4
LBI
10 PGND
PGOOD
1 EN
8
PGOOD
NC 3
GND
5, Exposed Pad (11)
Figure 2. Fixed Output Voltage Boost Converter with Voltage Detector
Functional Pin Description
Pin No.
Pin Name
Pin Function
1
EN
Chip Enable (Active High).
2
VOUT
Boost Output.
3
FB / NC
Feedback Input for Adjustable Output Voltage Version / No Internal Connection
for Fixed Output Voltage Version.
4
LBO
Voltage Detector Output.
5
GND
Ground.
6
VBAT
Battery Supply Input.
7
LBI
Voltage Detector Input.
8
PGOOD
Power Good Indicator.
9
LX
Switching Node. Connect this pin to an inductor.
10
PGND
Power Ground.
11 (Exposed Pad) GND
Ground. The exposed pad must be soldered to a large PCB and connected to
GND for maximum power dissipation.
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DS9276-02 July 2013
RT9276
Function Block Diagram
PGOOD VOUT
Determine
Higher Voltage
Soft-Start
Control
EN
OCP,
OTP,
OVP
VREF1
EA
FB
VBAT
Logic
UGATE
Control
Back Gate
Control
LX
PWM
LGATE
Current
Sense
GND
Internal
Compensation
PGND
LBO
VREF2
+
-
LBI
Figure 3. Adjustable Voltage Regulator
PGOOD VOUT
Determine
Higher Voltage
Soft-Start
Control
EN
VREF1
OCP,
OTP,
OVP
VOUT
VBAT
Logic
UGATE
Control
Back Gate
Control
LX
EA
LGATE
PWM
Current
Sense
PGND
GND
LBO
Internal
Compensation
VREF2
+
-
LBI
Figure 4. Fixed Voltage Regulator
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RT9276
Absolute Maximum Ratings
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(Note 1)
Supply Input Voltage, VBAT ---------------------------------------------------------------------------------------------Boost Output Voltage, VOUT -------------------------------------------------------------------------------------------Switch Output Voltage, LX ---------------------------------------------------------------------------------------------<10ns -----------------------------------------------------------------------------------------------------------------------Digital Input Voltage, EN, LBI -----------------------------------------------------------------------------------------Digital Output Voltage, LBO, PGOOD -------------------------------------------------------------------------------Others Pin ------------------------------------------------------------------------------------------------------------------Power Dissipation, PD @ TA = 25°C
WDFN-10L 3x3 ------------------------------------------------------------------------------------------------------------Package Thermal Resistance (Note 2)
WDFN-10L 3x3, θJA ------------------------------------------------------------------------------------------------------WDFN-10L 3x3, θJC ------------------------------------------------------------------------------------------------------Junction Temperature Range -------------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------Storage Temperature Range -------------------------------------------------------------------------------------------ESD Susceptibility (Note 3)
HBM (Human Body Mode) ---------------------------------------------------------------------------------------------MM (Machine Mode) ------------------------------------------------------------------------------------------------------
Recommended Operating Conditions
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−0.3V to 6V
−0.3V to 6.5V
−0.3V to 6.5V
−2V to 7.5V
−0.3V to 6V
−0.3V to 6V
−0.3V to 6V
1.429W
70°C/W
8.2°C/W
150°C
260°C
−65°C to 150°C
2kV
200V
(Note 4)
Supply Input Voltage Range, VBAT ------------------------------------------------------------------------------------- 1.2V to 5V
Junction Temperature Range -------------------------------------------------------------------------------------------- −40°C to 125°C
Ambient Temperature Range -------------------------------------------------------------------------------------------- −40°C to 85°C
Electrical Characteristics
(VBAT ≥ 2.5V or VBAT = VOUT + 0.7V, VEN = VBAT, CIN = 10μF, COUT = 22μF, TA = 25°C, unless otherwise specified)
Parameter
Pre-charge Current
Symbol
Test Conditions
Min
Typ
Max
Unit
IPre-chg
VIN = 5V
--
100
--
mA
VBAT
ILOAD = 1mA
--
1.2
--
V
0.8
--
5
V
--
--
5
V
0.49
0.5
0.51
V
−3
--
3
%
0.96
1.2
1.44
MHz
--
90
--
%
DC/DC Stage
Minimum Start-Up Input Voltage
Input Voltage Range After Start-Up VBAT
Output Voltage Range
VOUT
Feedback Reference Voltage
VFB
For Adjustable Output Voltage
Output Voltage Accuracy
ΔVOUT
For Fixed Output Voltage
Switching Frequency
fLX
Maximum Duty Cycle
DMAX
Non-Switching Quiescent Current
IQ,NS
No Switching
--
100
--
μA
Shutdown Current
ISHDN
VEN = 0, VBAT = 1.2V
--
2
5
μA
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is a registered trademark of Richtek Technology Corporation.
DS9276-02 July 2013
RT9276
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
Protection
Over-Temperature Protection
T OTP
--
170
--
°C
Over-Temperature Hysteresis
T OTP_Hys
--
40
--
°C
Over-Current Protection
IOCP
1.6
2
2.4
A
Over-Voltage Protection
VOVP
5.4
--
6
V
VOUT = 3.3V
--
220
--
VOUT = 5V
--
200
--
VOUT = 3.3V
--
260
--
VOUT = 5V
--
240
--
VOUT = 3.3V
Power MOSFET
N-MOSFET ON-Resistance
RDS(ON)_N
P-MOSFET ON-Resistance
RDS(ON)_P
mΩ
mΩ
Enable Control
EN Threshold
Voltage
Logic-High
VIH
Rising
0.8
--
--
Logic-Low
VIL
Falling
--
--
0.2
0.49
0.5
0.51
V
--
10
--
mV
--
15
--
Ω
V
Voltage Detector
LBI Voltage Threshold
VLBI_Rising
LBI Voltage Hysteresis
VLBI_Hys
LBO Output Impedance
RON_LBO
VLBI = 0V, VOUT = 3.3V
Note 1. Stresses beyond those listed “Absolute Maximum Ratings” may cause permanent damage to the device. These are
stress ratings only, and 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 may affect
device reliability.
Note 2. θJA is measured at TA = 25°C on a high effective thermal conductivity four-layer test board per JEDEC 51-7. θJC is
measured at the exposed pad of the package.
Note 3. Devices are ESD sensitive. Handling precaution is recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
Copyright © 2013 Richtek Technology Corporation. All rights reserved.
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RT9276
Typical Operating Characteristics
μF, COUT = 22μ
μF, L = 4.7μ
μH, unless otherwise specified.
CIN = 10μ
Efficiency vs. Load Current
Efficiency vs. Load Current
100
100
90
90
80
VIN = 3V
VIN = 2.4V
VIN = 1.8V
VIN = 1.2V
VIN = 0.9V
70
60
50
40
Efficiency (%)
Efficiency (%)
80
30
20
10
70
VIN = 4.2V
VIN = 3.6V
VIN = 3V
VIN = 2.4V
VIN = 1.8V
60
50
40
30
20
10
VOUT = 3.3V
0
0.001
0.01
0.1
VOUT = 5V
0
0.001
1
0.01
Load Current (A)
100
90
90
80
IOUT = 100mA
IOUT = 10mA
Efficiency (%)
Efficiency (%)
80
60
IOUT = 200mA
50
40
30
20
10
IOUT = 100mA
IOUT = 10mA
70
60
50
40
30
20
10
VOUT= 3.3V
VOUT = 5V
0
0
0.9
1.4
1.9
2.4
2.9
3.4
0.9
1.4
Input Voltage (V)
5.2
3.35
5.1
Output Voltage (V)
3.30
VIN = 3V
VIN = 2.4V
VIN = 1.8V
VIN = 1.2V
VIN = 0.9V
3.20
3.15
2.4
2.9
3.4
3.9
4.4
4.9
Output Voltage vs. Load Current
3.40
3.25
1.9
Input Voltage (V)
Output Voltage vs. Load Current
Output Voltage (V)
1
Efficiency vs. Input Voltage
Efficiency vs. Input Voltage
100
70
0.1
Load Current (A)
3.10
5.0
VIN = 4.2V
VIN = 3.6V
VIN = 3V
VIN = 2.4V
VIN = 1.8V
VIN = 1.2V
VIN = 0.9V
4.9
4.8
4.7
4.6
3.05
VOUT = 3.3V
3.00
0.001
0.01
0.1
Load Current (A)
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1
VOUT = 5V
4.5
0.001
0.01
0.1
1
Load Current (A)
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DS9276-02 July 2013
RT9276
Switching
Output Voltage vs. Input Voltage
6.0
Output Voltage (V)
5.5
5.0
VIN
(1V/Div)
VOUT
(50mV/Div)
IOUT= 10mA
IOUT= 100mA
4.5
4.0
VLX
(5V/Div)
3.5
3.0
ILX
(500mA/Div)
2.5
VOUT = 5V
VBAT = 1.2V, VOUT = 3.3V, ILOAD = 100mA
2.0
0.9
1.4
1.9
2.4
2.9
3.4
3.9
4.4
Time (250ns/Div)
4.9
Input Voltage (V)
Load Transient Response
Switching
VIN
(2V/Div)
VOUT
(100mV/Div)
VIN
(2V/Div)
VOUT
(50mV/Div)
VLX
(5V/Div)
ILX
(500mA/Div)
IOUT
(100mA/Div)
VBAT = 2.4V, VOUT = 3.3V, ILOAD = 100mA to 200mA
VBAT = 2.4V, VOUT = 3.3V, ILOAD = 200mA
Time (500μs/Div)
Time (250ns/Div)
Line Transient Response
Switching Frequency vs. Temperature
Switching Frequency (kHz)
1300
VIN
(2V/Div)
VOUT
(100mV/Div)
IOUT
(100mA/Div)
1250
1200
1150
1100
1050
VIN = 1.8V
VIN = 2.4V
1000
950
VBAT = 1.8V to 2.4V, VOUT = 3.3V, ILOAD = 100mA
VOUT = 3.3V
900
Time (500μs/Div)
-40 -25 -10
5
20
35
50
65
80
95 110 125
Temperature (°C)
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RT9276
Voltage Detector Response
FB Reference Voltage vs. Temperature
0.55
FB Reference Voltage (V)
0.54
0.53
0.52
0.51
0.50
VIN = 1.8V
VIN = 2.4V
0.49
LBO
(2V/Div)
0.48
0.47
0.46
LBI
(500mV/Div)
VBAT = 1.8V, VOUT = 5V, RLBO = 200kΩ
VOUT = 3.3V
0.45
-40 -25 -10
5
20
35
50
65
80
95 110 125
Time (1ms/Div)
Temperature (°C)
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RT9276
Application Information
The RT9276 integrates a high efficiency synchronous stepup DC-DC converter and a low battery detector. To fully
utilize its advantages, peripheral components should be
appropriately selected. The following information provides
detailed description of application.
Inductor Selection
For a better efficiency in high switching frequency
converter, the inductor selection has to use a proper core
material such as ferrite core to reduce the core loss and
choose low ESR wire to reduce copper loss. The most
important point is to prevent core saturation when handling
the maximum peak current. Using a shielded inductor can
minimize radiated noise in sensitive applications. The
maximum peak inductor current is the maximum input
current plus half of the inductor ripple current. The
calculated peak current has to be smaller than the current
limitation in the electrical characteristics. A typical setting
of the inductor ripple current is 20% to 40% of the
maximum input current. If the selection is 40%
1
IPK = IIN(MAX) + IRIPPLE = 1.2 × IIN(MAX)
2
⎡ IOUT(MAX) × VOUT ⎤
= 1.2 × ⎢
⎥
⎣ η × VBAT(MIN) ⎦
The minimum inductance value is derived from the following
equation :
L=
η × IIN(MIN)2 × [ VOUT − VBAT(MIN) ]
0.4 × IOUT(MAX) × VOUT 2 × fLX
Depending on the application, the recommended inductor
value is between 2.2μH and 10μH.
Input Capacitor Selection
For better input bypassing, low-ESR ceramic capacitors
are recommended for performance. A 10μF input capacitor
is sufficient for most applications. For a lower output power
requirement application, this value can be decreased
one is the pulsating output ripple current which flows
through the ESR, and the other is the capacitive ripple
caused by charging and discharging.
VRIPPLE = VRIPPLE(ESR) + VRIPPLE(C)
≅ IPEAK × RESR +
IPEAK ⎡ VOUT − VBAT ⎤
COUT ⎢⎣ VOUT × fLX ⎥⎦
Output Voltage Setting
Referring to application circuit (Figure 1), the output
voltage of the switching regulator (VOUT) can be set with
below equation :
⎛ R3 ⎞
VOUT = ⎜ 1 +
⎟ × VFB
⎝ R4 ⎠
where VFB = 0.5V (typ.)
When the input voltage is larger than output setting voltage
370mV (typ.) the RT9276 will be in pre-charge mode.
During pre-charge phase, the synchronous P-MOSFET
is turned on until the output capacitor is charged to a
value close to the input voltage minus 0.2V. Then the
converter is followed by PWM operation. The adaptive precharge current increases linearly to overcome the loading
current in the pre-charge phase. If the loading current is
larger than pre-charge current, the RT9276 will be in precharge mode until loading current is removed or reduced.
Low Battery Voltage Detector
The low battery voltage detector is designed to monitor
the battery voltage and to generate an error flag when the
battery voltage drops below a user-set threshold voltage.
The function is active only when the device is enabled.
When the device is disabled, the LBO pin is in high
impedance. The LBI threshold voltage is 0.5V typically,
with 10mV hysteresis voltage. If the low-battery detection
circuit is not used, the LBI pin should be connected to
GND (or to VBAT) and the LBO pin can be left unconnected.
Do not let the LBI pin floating.
Thermal Considerations
Output Capacitor Selection
For lower output voltage ripple, low ESR ceramic capacitors
are recommended. The tantalum capacitors can be used
as well, but their ESR is bigger than ceramic capacitors.
The output voltage ripple consists of two components:
Copyright © 2013 Richtek Technology Corporation. All rights reserved.
DS9276-02 July 2013
For continuous operation, do not exceed absolute
maximum operation junction temperature. The maximum
power dissipation depends on the thermal resistance of
IC package, PCB layout, the rate of surroundings airflow
and temperature difference between junction to ambient.
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RT9276
The maximum power dissipation can be calculated by
following formula :
PD(MAX) = (TJ(MAX) − TA) / θJA
Layout Consideration
For best performance of the RT9276, the following layout
guidelines must be strictly followed :
where T J(MAX) is the maximum operation junction
temperature, TA is the ambient temperature and the θJA is
the junction to ambient thermal resistance.
`
Input and Output capacitors should be placed close to
the IC and connected to ground plane to reduce noise
coupling.
For recommended operating conditions specification, the
maximum junction temperature is 125°C. The junction to
ambient thermal resistance θJA is layout dependent. For
WDFN-10L 3x3 package, the thermal resistance θJA is
70°C/W on a standard JEDEC 51-7 four- layer thermal
test board. The maximum power dissipation at TA = 25°C
can be calculated by the following formula :
`
The GND and Exposed Pad should be connected to a
strong ground plane for heat sinking and noise protection.
`
Keep the main current traces as short and wide as
possible.
`
Place the feedback components as close as possible
to the IC and keep away from the noisy devices.
The maximum power dissipation depends on operating
ambient temperature for fixed T J(MAX) and thermal
resistance θJA. The Figure 5 of derating curves allows the
designer to see the effect of rising ambient temperature
on the maximum power dissipation.
Maximum Power Dissipation (W)
1.6
Four-Layer PCB
1.4
Cin and Cout should be placed close to the IC
and connected to ground plane to reduce
noise coupling.
CIN V
BAT
COUT
10 PGND
EN 1
L
FB node copper
9 LX
VOUT 2
R3
area should be
3
8 PGOOD
FB/NC
VOUT
minimized and
7 LBI
LBO 4
R4
11
5
6
kept far away from
VBAT
GND
noise sources (LX
pin)
GND
The GND and Exposed Pad should be
connected to a strong ground plane
for heat sinking and noise protection.
GND
PD(MAX) = (125°C − 25°C) / (70°C/W) = 1.429W for
WDFN-10L 3x3 packages
Figure 6. PCB Layout Guide
1.2
WDFN-10L 3x3
1.0
0.8
0.6
0.4
0.2
0.0
0
25
50
75
100
125
Ambient Temperature (°C)
Figure 5. Derating Curve of Maximum Power Dissipation
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DS9276-02 July 2013
RT9276
Outline Dimension
D2
D
L
E
E2
1
e
SEE DETAIL A
b
2
1
2
1
A
A1
A3
DETAIL A
Pin #1 ID and Tie Bar Mark Options
Note : The configuration of the Pin #1 identifier is optional,
but must be located within the zone indicated.
Dimensions In Millimeters
Dimensions In Inches
Symbol
Min
Max
Min
Max
A
0.700
0.800
0.028
0.031
A1
0.000
0.050
0.000
0.002
A3
0.175
0.250
0.007
0.010
b
0.180
0.300
0.007
0.012
D
2.950
3.050
0.116
0.120
D2
2.300
2.650
0.091
0.104
E
2.950
3.050
0.116
0.120
E2
1.500
1.750
0.059
0.069
e
L
0.500
0.350
0.020
0.450
0.014
0.018
W-Type 10L DFN 3x3 Package
Richtek Technology Corporation
5F, No. 20, Taiyuen Street, Chupei City
Hsinchu, Taiwan, R.O.C.
Tel: (8863)5526789
Richtek products are sold by description only. Richtek reserves the right to change the circuitry and/or specifications without notice at any time. Customers should
obtain the latest relevant information and data sheets before placing orders and should verify that such information is current and complete. Richtek cannot
assume responsibility for use of any circuitry other than circuitry entirely embodied in a Richtek product. Information furnished by Richtek is believed to be
accurate and reliable. However, no responsibility is assumed by Richtek or its subsidiaries for its use; nor for any infringements of patents or other rights of third
parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Richtek or its subsidiaries.
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