RT9296 - Richtek
RT9296
Synchronous Boost Converter with LDO Controller
General Description
Features
The RT9296 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 the power save
mode to maintain a high efficiency over a wide load current
range.
z
True Load Disconnection During Shutdown
z
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
Linear Controller
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 10-Lead WDFN Package
RoHS Compliant and Halogen Free
The output voltage can be programmed by an external
resistor divider, or be a fixed voltage. Moreover, the
converter can be disabled to the 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.
z
z
z
z
z
z
z
z
z
z
z
z
For the RT9296, a low-EMI (anti-ringing) mode is
implemented (by trim option) to reduce ringing of the
inductor phase pin when the converter enters the
discontinuous conduction mode. Moreover, a linear
controller is built-in in the chip for linear regulator
application.
Ordering Information
z
Applications
z
z
z
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)
Lead Plating System
G : Green (Halogen Free and Pb Free)
Boost VOUT
Default : Adjustable
33 : 3.3V
50 : 5.0V
Note :
Pin Configurations
(TOP VIEW)
EN
VOUT
FB/NC
DRV
GND
1
2
3
4
5
GND
RT9296(-
z
11
10
9
8
7
6
PGND
LX
PGOOD
FBL
VBAT
WDFN-10L 3x3
Richtek products are :
`
RoHS compliant and compatible with the current require-
Marking Information
ments of IPC/JEDEC J-STD-020.
`
Suitable for use in SnPb or Pb-free soldering processes.
DS9296-01 April 2011
For marking information, contact our sales representative
directly or through a Richtek distributor located in your
area.
www.richtek.com
1
RT9296
Typical Application Circuit
L
4.7µH
V BAT
C IN
10µF
RT9296
VOUT 2
9 LX
V OUT
6 VBAT
R4
V OUT
Chip Enable
R1
DRV 4
8
1
5, Exposed Pad (11)
Q1
C OUT
22µF
LDO
PGOOD
R2
EN
C LDO
FBL 7
PGND 10
GND
R3
Figure 1. Fixed Output Voltage Boost Converter with Linear Regulator
L
4.7µH
V BAT
C IN
10µF
VOUT 2
V OUT
6 VBAT
R5
V OUT
RT9296
9 LX
Chip Enable
R1
FB 3
8
1
5, Exposed Pad (11)
PGOOD
EN
C OUT
22µF
R3
R2
DRV 4
PGND 10
GND
Q1
WLED
FBL 7
R4
Figure 2. Adjustable Output Voltage Boost Converter with WLED Driver
Functional Pin Description
Pin No.
Pin Name
Pin Function
1
EN
Chip Enable (Active High).
2
VOUT
Boost Output.
3
FB / NC
Feedback Pin / No Internal Connection.
4
DRV
Driver of Linear Controller.
5
GND
Ground.
6
VBAT
Battery Supply Input.
7
FBL
Feedback Input Linear Controller.
8
PGOOD
Power Good Indicator.
9
LX
Switching Node. Connect this Pin to an inductor.
10
PGND
Power Ground.
11 (Exposed Pad) GND
www.richtek.com
2
Ground. The exposed pad must be soldered to a large PCB and connected to
GND for maximum power dissipation.
DS9296-01 April 2011
RT9296
Function Block Diagram
PGOOD
Determine
Higher Voltage
Soft-Start
Control
EN
V REF1
OCP,
OTP,
OVP
V OUT
EA
VBAT
VOUT
Logic
Control
Back Gate
Control
UGATE
LX
PWM
LGATE
Current
Sense
GND
PGND
DRV
Internal
Compensation
V REF2
+
-
FBL
Figure 3. Fixed Voltage Regulator
PGOOD
V REF1
FB
Determine
Higher Voltage
Soft-Start
Control
EN
OCP,
OTP,
OVP
EA
VBAT
VOUT
Logic
Control
UGATE
Back Gate
Control
LX
PWM
LGATE
Current
Sense
GND
PGND
DRV
Internal
Compensation
V REF2
+
-
FBL
Figure 4. Adjustable Voltage Regulator
DS9296-01 April 2011
www.richtek.com
3
RT9296
Absolute Maximum Ratings
z
z
z
z
z
z
z
z
z
z
z
z
(Note 1)
Supply Input Voltage, VBAT ---------------------------------------------------------------------------------------------Boost Output Voltage, VOUT -------------------------------------------------------------------------------------------Switch Output Voltage, LX ---------------------------------------------------------------------------------------------Digital Input Voltage, EN, FBL ----------------------------------------------------------------------------------------Digital Output Voltage, DRV, 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
z
z
z
−0.3V to 6V
−0.3V to 6.5V
−0.3V to 6.5V
−0.3V to 6V
−0.3V to 6V
−0.3V to 6V
1.429W
70°C/W
7.8°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
Symbol
Test Conditions
Min
Typ
Max
Unit
--
1.2
--
V
0.8
--
5
V
--
--
5
V
0.49
0.5
0.51
--
0.1
--
0.49
0.5
0.51
V
−3
--
+3
%
DC/DC Stage
Start-Up Input Voltage
V BAT
ILoad = 1mA
Input Voltage Range After Start-Up V BAT
Output Voltage Range
V OUT
EN Threshold Voltage
V EN
Rising Threshold Voltage
V
Hysteresis Voltage
Feedback Reference Voltage
V FB
For Adjustable Output Voltage
Output Voltage Accuracy
ΔVOUT
For Fixed Output Voltage
Switching Frequency
fSW
--
1.2
--
MHz
Maximum Duty Cycle
DMAX
--
90
--
%
Non-Switching Quiescent Current
IQ,NS
No Switching
--
100
--
μA
Shutdown Current
ISHDN
V EN = 0, VBAT = 1.2V
--
10
--
μA
To be continued
www.richtek.com
4
DS9296-01 April 2011
RT9296
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
V OVP
5.5
--
6.5
V
V OUT = 3.3V
Power MOSFET
N-MOSFET ON-Resistance
RDS(ON)_N V OUT = 3.3V
--
260
--
mΩ
P-MOSFET ON-Resistance
RDS(ON)_P V OUT = 3.3V
--
290
--
mΩ
0.19
0.2
0.21
V
--
2
--
kΩ
Linear Controller
FBL Reference Voltage
V FBL
Output Impedance of Linear
Controller
RON_LBO
V LBI = 0V
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.
Note 2. θJA is measured in the natural convection at TA = 25°C on a high effective four layers thermal conductivity test board of
JEDEC 51-7 thermal measurement standard. The case point of θJC is on the expose pad for the WDFN package.
Note 3. Devices are ESD sensitive. Handling precaution is recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
DS9296-01 April 2011
www.richtek.com
5
RT9296
Typical Operating Characteristics
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
Efficiency (%)
Efficiency (%)
80
40
30
20
VIN = 4.2V
VIN = 3.6V
VIN = 3V
VIN = 2.4V
VIN = 1.8V
70
60
50
40
30
20
10
10
VOUT = 3.3V
0
0.001
0.01
0.1
VOUT = 5V
0
0.001
1
0.01
Load Current (A)
Efficiency vs. Input Voltage
100
90
90
60
Efficiency (%)
Efficiency (%)
80
IOUT = 100mA
IOUT = 10mA
70
IOUT = 200mA
50
40
30
IOUT = 10mA
70
IOUT = 100mA
60
50
40
30
20
20
10
10
VOUT = 5V
VOUT= 3.3V
0
0
0.9
1.4
1.9
2.4
2.9
0.9
3.4
1.4
Output Voltage vs. Load Current
2.9
3.4
3.9
4.4
4.9
Output Voltage vs. Load Current
3.35
5.0
Output Voltage (V)
3.30
VIN = 3V
VIN = 2.4V
VIN = 1.8V
VIN = 1.2V
VIN = 0.9V
3.25
3.20
3.15
3.10
4.9
VIN = 4.2V
VIN = 3.6V
VIN = 3V
VIN = 2.4V
VIN = 1.8V
VIN = 1.2V
4.8
4.7
4.6
3.05
0.01
0.1
Load Current (A)
www.richtek.com
6
2.4
5.1
3.40
VOUT = 3.3V
3.00
0.001
1.9
Input Voltage (V)
Input Voltage (V)
Output Voltage (V)
1
Efficiency vs. Input Voltage
100
80
0.1
Load Current (A)
1
VOUT = 5V
4.5
0.001
0.01
0.1
1
Load Current (A)
DS9296-01 April 2011
RT9296
Switching Frequency vs. Temperature
1300
5.5
1250
Switching Frequency (kHz)
Output Voltage (V)
Output Voltage vs. Input Voltage
6.0
5.0
IOUT= 10mA
IOUT= 100mA
4.5
4.0
3.5
3.0
2.5
1200
1150
1100
1050
1000
950
VOUT = 5V
VIN = 3.6V, VOUT = 5V
900
2.0
0.9
1.4
1.9
2.4
2.9
3.4
3.9
4.4
-50
4.9
-25
0
25
0.54
0.24
0.53
0.52
0.51
0.50
0.49
0.48
0.47
0.46
VIN = 3.6V, VOUT = 5V
25
50
0.22
0.21
0.20
0.19
0.18
0.17
0.16
75
100
0
25
50
75
100
125
CCM Switching
VIN
(2V/Div)
VIN
(2V/Div)
VOUT
(20mV/Div)
VOUT
(50mV/Div)
ILX
(200mA/Div)
VLX
(5V/Div)
DS9296-01 April 2011
-25
Temperature (°C)
DCM Switching
VBAT = 3.6V, VOUT = 5V, ILOAD = 20mA
VIN = 3.6V, VOUT = 5V
-50
125
Temperature (°C)
Time (1μs/Div)
125
0.23
0.15
0.45
0
100
FBL Reference Voltage vs Temperature
0.25
FBL Reference Voltage (V)
FB Reference Voltage (V)
FB Reference Voltage vs. Temperature
0.55
-25
75
Temperature (°C)
Input Voltage (V)
-50
50
ILX
(500mA/Div)
VBAT = 3.6V, VOUT = 5V, ILOAD = 200mA
Time (250ns/Div)
www.richtek.com
7
RT9296
Line Transient Response
Load Transient Response
VIN
(2V/Div)
VIN
(2V/Div)
VOUT
(100mV/Div)
VOUT
(100mV/Div)
IOUT
(200mA/Div)
IOUT
(200mA/Div)
VBAT = 3.6V, VOUT = 5V, ILOAD = 100mA to 200mA
Time (500μs/Div)
www.richtek.com
8
VBAT = 3V to 3.6V, VOUT = 5V, ILOAD = 200mA
Time (500μs/Div)
DS9296-01 April 2011
RT9296
Application Information
The RT9296 integrates a high-efficiency synchronous stepup DC-DC converter and a linear regulator controller. 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 the 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 the half of 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 × VIN(MIN)
⎦
The minimum inductance value is derived from the following
equation :
L=
η × IIN(MIN)2 × [ VOUT − VIN(MIN) ]
0.4 × IOUT(MAX) × VOUT 2 × fSW
Depending on the application, the recommended inductor
value is between 2.2μH and 10μH.
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 − VIN ⎤
COUT ⎢⎣ VOUT × fSW ⎥⎦
Output Voltage Setting
Referring to application circuit (Figure 2), the output
voltage of the switching regulator (VOUT) can be set with
below equation :
R1 ⎞
⎛
VOUT = ⎜ 1 +
⎟ × VFB
⎝ R2 ⎠
where VFB = 0.5V (typ.)
Linear Regulator
The RT9296 integrates a linear controller with an opendrain output. An external P-MOSFET and external
feedback resistors are required for this application. The
feedback voltage is set at 0.2V typically.
For linear regulator application, the output voltage can be
set by an external voltage resistive divider. For WLED driver
application, the LED current can be set by an external
feedback resistor.
Thermal Considerations
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.
The maximum power dissipation can be calculated by
following formula :
Input Capacitor Selection
PD(MAX) = (TJ(MAX) − TA) / θJA
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
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.
Output Capacitor Selection
For lower output voltage ripple, low-ESR ceramic
capacitors are recommended. The tantalum capacitors can
be used as well, but the ESR is bigger than ceramic
capacitor. The output voltage ripple consists of two
components: one is the pulsating output ripple current
DS9296-01 April 2011
For recommended operating conditions specification of
RT9296, the maximum junction temperature is 125°C. The
junction to ambient thermal resistance θJA is layout
dependent. For WDFN-10L 3x3 packages, the thermal
resistance θJA is 70°C/W on the standard JEDEC 51-7
four layers thermal test board. The maximum power
dissipation at TA = 25°C can be calculated by following
www.richtek.com
9
RT9296
PD(MAX) = (125°C − 25°C) / (70°C/W) = 1.429W for
WDFN-10L 3x3 packages
The maximum power dissipation depends on operating
ambient temperature for fixed T J(MAX) and thermal
resistance θJA. For RT9296 packages, the Figure 5 of
derating curves allows the designer to see the effect of
rising ambient temperature on the maximum power
allowed.
V BAT
C OUT
10 PGND
EN 1
L
FB node copper
9 LX
VOUT 2
R1
area should be
8 PGOOD
FB/NC 3
V OUT
minimized and
7 FBL
DRV 4
R2
11
6 VBAT
keep far away from
GND 5
noise sources (LX
pin)
GND
The GND and Exposed Pad should be
connected to a strong ground plane
for heat sinking and noise protection.
Figure 6. PCB Layout Guide
1.6
Maximum Power Dissipation (W)
C IN and C OUT should be placed close to the
IC and connected to ground plane to reduce
noise coupling.
C IN
GND
formula :
Four Layers PCB
1.4
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 Curves for RT9296 Packages
Layout Consideration
For Best performance of RT9296, the following layout
guidelines must be strictly followed.
`
Input and Output capacitors should be placed close to
the IC and connected to ground plane to reduce noise
coupling.
`
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 possible as short and
wide.
`
Place the feedback components as close as possible
to the IC and keep away from the noisy devices.
www.richtek.com
10
DS9296-01 April 2011
RT9296
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
Richtek Technology Corporation
Headquarter
Taipei Office (Marketing)
5F, No. 20, Taiyuen Street, Chupei City
5F, No. 95, Minchiuan Road, Hsintien City
Hsinchu, Taiwan, R.O.C.
Taipei County, Taiwan, R.O.C.
Tel: (8863)5526789 Fax: (8863)5526611
Tel: (8862)86672399 Fax: (8862)86672377
Email: marketing@richtek.com
Information that is provided by Richtek Technology Corporation is believed to be accurate and reliable. Richtek reserves the right to make any change in circuit
design, specification or other related things if necessary without notice at any time. No third party intellectual property infringement of the applications should be
guaranteed by users when integrating Richtek products into any application. No legal responsibility for any said applications is assumed by Richtek.
DS9296-01 April 2011
www.richtek.com
11
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF

advertising