PANASONIC AN30888A

DATA SHEET
Part No.
AN30888A
Package Code No.
SSOP016-P-0225E
Publication date: December 2010
Ver. AEB
1
AN30888A
Contents
„ Overview ……………………………………………………………………………………………………………. 3
„ Features ……………………………………………………………………………………………………………. 3
„ Applications ……………………………………….……………………………………………………………….. 3
„ Package ……………………………………………………………………………………………………………. 3
„ Type ……………………………………………….………………………………………………………………… 3
„ Application Circuit Example (Block Diagram) ………………………………………………………………….. 4
„ Pin Descriptions ………………………….………………………………………………………………………... 7
„ Absolute Maximum Ratings ……………………………………………………………………………………… 8
„ Operating Supply Voltage Range ……………………………………………………………………………….. 8
„ Allowable Voltage Range …………………………………………………………………………………………. 9
„ Electrical Characteristics …………………………………………………………………………………………. 10
„ Electrical Characteristics (Reference values for design) ……………………………………………………… 11
„ Control Pin Mode Table
………………………………………………………………………………………….. 12
„ Electrical Characteristics Test Procedures …………………………………………………………………….. 13
„ Technical Data …………………………………………………………………………………………………….. 16
y I/O block circuit diagrams and pin function descriptions
…………………………………………………….. 16
y Functions and properties descriptions …………………………………………………………………………. 19
y PD ⎯ Ta diagram …………………………………………………………………………………………………. 29
„ Usage Notes
………………………………………………………………………………………………………. 30
y Special attention and precaution in using ……………………………………………………………………… 30
Ver. AEB
2
AN30888A
AN30888A
High Brightness LED Driver IC
„ Overview
AN30888A is a Boost/Buck-Boost/Buck DCDC controller that drives an external power NMOS switch.
It is suitable for driving high brightness LED for LED lighting applications.
„ Features
y Battery operation :
3 V to 20 V
y Output current range :
0 A to a few Amperes depending on rating of external NMOS and mode of operation
y Current mode control architecture
y LED dimming function available by using PWM signal
y 30 mV / 200 mV reference voltage
y Low standby current
y Configurable as either Boost/Buck-Boost/ Buck mode converter
y Built-in various protection circuit : Under voltage lock out
Over voltage protection
Soft start function
„ Applications
y LED lighting module
y LED lantern applications
y White LED backlighting for LCD panel
y White LED flash light driving applications
y General LED back lighting
„ Package
y 16 pin Plastic Shrink Small Outline Package (SSOP Type)
„ Type
y Bi–CMOS IC
Ver. AEB
3
AN30888A
„ Application Circuit Example (Block Diagram)
y Boost Mode
VIN
16 VREG
L
4
BGR
ENB
14
2.2 μF
1 μF
3.65 V
11 SW
EN
UVLO
6 CS
CONTROL
PWM
D
VREG
1.262 V
VIN
VOUT
12
IPK
ILED
VFB
RCS
9
GNDP
R1
VFB_SEL
5
Reference
voltage
8 OVP
GND
1
R2
Notes) y This application circuit is an example. The operation of mass production set is not guaranteed. Perform enough evaluation and verification on
the design of mass production set.
y Use external resistor with ±1% accuracy at CS pin.
y Use ceramic type capacitor (Typ. 1 μF, Min. 0.5 μF) at VREG pin.
y Use schottky diode at VOUT.
y This block diagram is for explaining functions. The part of the block diagram may be omitted, or it may be simplified.
Ver. AEB
4
AN30888A
„ Application Circuit Example (Block Diagram) (continued)
y Buck-Boost Mode
L
VOUT
D
VIN
16 VREG
2.2 μF
4
BGR
VIN
VREG
3.65 V
1.262 V
ENB
14
1 μF
11 SW
EN
UVLO
6 CS
CONTROL
PWM
IPK
ILED
VFB
RCS
12
9 GNDP
VFB_SEL
5
Reference
voltage
8 OVP
R1
GND
1
R2
Notes) y This application circuit is an example. The operation of mass production set is not guaranteed. Perform enough evaluation and verification on
the design of mass production set.
y Use external resistor with ±1% accuracy at CS pin.
y Use ceramic type capacitor (Typ. 1 μF, Min. 0.5 μF) at VREG pin.
y Use schottky diode at VOUT.
y This block diagram is for explaining functions. The part of the block diagram may be omitted, or it may be simplified.
Ver. AEB
5
AN30888A
„ Application Circuit Example (Block Diagram) (continued)
VIN
16 VREG
y Buck Mode
4
BGR
ENB
14
2.2 μF
L
3.65 V
11 SW
EN
UVLO
IPK
6 CS
CONTROL
PWM
D
VREG
1.262 V
VIN
1 μF
ILED
VFB
VOUT
RCS
12
9 GNDP
VFB_SEL
5
Reference
voltage
GND
1
8 OVP
Notes) y This application circuit is an example. The operation of mass production set is not guaranteed. Perform enough evaluation and verification on
the design of mass production set.
y Use external resistor with ±1% accuracy at CS pin.
y Use ceramic type capacitor (Typ. 1 μF, Min. 0.5 μF) at VREG pin.
y Use schottky diode at VOUT.
y This block diagram is for explaining functions. The part of the block diagram may be omitted, or it may be simplified.
Ver. AEB
6
AN30888A
„ Pin Descriptions
Pin No.
Pin name
Type
Description
1
GND
Ground
2
N.C.
—
—
3
N.C.
—
—
4
VIN
Power Supply
5
VFB_SEL
Input
Feedback voltage select
6
CS
Input
Current Sense
7
N.C.
—
8
OVP
Input
9
GNDP
Ground
10
N.C.
—
11
SW
Output
12
PWM
Input
13
N.C.
—
14
ENB
Input
15
N.C.
—
16
VREG
Output
Ground
Power Supply of IC
—
Over Voltage Protection input pin for Boost mode; Connect to GND for Buck mode
Power Ground
—
External NMOS Transistor Gate Drive
PWM Dimming Control
—
Standby On/Off Control
—
Regulator Output
Ver. AEB
7
AN30888A
„ Absolute Maximum Ratings
Note) Absolute maximum ratings are limit values which do not result in damages to this IC, and IC operation is not guaranteed at these limit values.
A No.
Parameter
Symbol
Rating
Unit
Notes
1
Supply voltage
VDD
21
V
*1
2
GND pin current
IGND
—
A
—
3
Power dissipation
PD
135
mW
*2
4
Operating ambient temperature
Topr
–25 to +85
°C
*3
5
Storage temperature
Tstg
–55 to +125
°C
*3
Notes) *1 : The values under the condition not exceeding the above absolute maximum ratings and the power dissipation.
*2 : The power dissipation shown is the value at Ta = 85°C for the independent (unmounted) IC package without a heat sink.
When using this IC, refer to the • PD-Ta diagram in the „ Technical Data standard and design the heat radiation with sufficient margin so that
the allowable value might not be exceeded based on the conditions of power supply voltage, load, and ambient temperature.
*3 : Except for the power dissipation, operating ambient temperature, and storage temperature, all ratings are for Ta = 25°C.
„ Operating Supply Voltage Range
Parameter
Symbol
Range
Unit
Notes
Supply voltage range
VIN
3.0 to 20
V
*1
Supply voltage range (Boost Mode/Buck-Boost
Mode)
VIN1
3.0 to 12
V
*1
Supply voltage range (Buck Mode)
VIN2
3.0 to 20
V
*1
Note) *1 : The values under the condition not exceeding the above absolute maximum ratings and the power dissipation.
Ver. AEB
8
AN30888A
„ Allowable Voltage Range
Notes) y Allowable current and voltage ranges are limit ranges which do not result in damages to this IC, and IC operation is not guaranteed within
these limit ranges.
y Voltage values, unless otherwise specified, are with respect to GND.
y VIN is voltage for VIN pin.
y Do not apply external currents or voltages to any pin not specifically mentioned.
Pin No.
Pin name
Rating
Unit
Note
4
VIN
– 0.3 to 20
V
*1
5
VFB_SEL
– 0.3 to 5.5
V
—
6
CS
– 0.3 to VREG
V
*2
8
OVP
– 0.3 to VREG
V
*2
11
SW
– 0.3 to VREG
V
*2
12
PWM
– 0.3 to 5.5
V
*2
14
ENB
– 0.3 to VIN
V
*1
16
VREG
– 0.3 to 4.3
V
*2
Notes) *1 :VIN must not exceed 20 V.
*2 :VREG must not exceed 4.3 V.
Ver. AEB
9
AN30888A
„ Electrical Characteristics at VIN = 6 V, ENB = 6 V, PWM = VREG
Note) Ta = 25°C±2°C unless otherwise specified.
B
No.
Parameter
Symbol
Conditions
Limits
Min
Typ
Max
Unit
Notes
Circuit Current Consumption
1
Standby Current
ISTB
ENB = 0 V
—
—
10
μA
—
2
Operating Quiescent Current
ICC
ENB = VIN
No load condition
—
—
1
mA
—
ENABLE (ENB), VFB_SEL and PWM Control Function
3
ENB High Input Logic
VENBH
—
3
—
VIN
V
—
4
ENB Low Input Logic
VENBL
—
0
—
0.3
V
—
5
VFB_SEL High Input Logic
VVFBSELH
—
0.7 ×
VREG
—
5
V
—
6
VFB_SEL Low Input Logic
VVFBSELL
—
0
—
0.3 ×
VREG
V
—
7
PWM High input Logic
VPWMH
—
0.7 ×
VREG
—
5
V
—
8
PWM Low input Logic
VPWML
—
0
—
0.3 ×
VREG
V
—
—
—
25
μA
—
Input Pin Current Consumption
9
Enable Pin Current
IENB
ENB = 6 V
Output Driver
10
SW High Output Logic
VSWH
SW output High logic;
MOSFET ON condition
0.7 ×
VREG
—
VREG +
0.2
V
—
11
SW Low Output Logic
VSWL
SW output Low logic;
MOSFET OFF condition
– 0.2
—
0.2
V
—
Under Voltage Lock Out (UVLO)
12
Under Voltage protection on value
VUVLOON
VIN Falling SW OFF;
VREG = no load
1.9
2.1
2.3
V
—
13
Under voltage protection Hysteresis
VUVLOHYS
VIN Rising SW ON –
VIN Falling SW OFF;
VREG = no load
0.1
0.3
0.5
V
—
Ver. AEB
10
AN30888A
„ Electrical Characteristics (Reference values for design) at VIN = 6 V
Note) Ta = 25°C±2°C unless otherwise specified.
The characteristics listed below are reference values derived from the design of the IC and are not guaranteed by inspection.
If a problem does occur related to these characteristics, we will respond in good faith to user concerns.
B No.
Parameter
Symbol
Conditions
Reference values
Min
Typ
Max
Unit
Notes
Reference Voltage Control
14
VFB Reference Voltage 1
VVFB1
VFB_SEL = High
OVP = 0 V
(Buck mode)
196
202
208
mV
—
15
VFB Reference Voltage 2
VVFB2
VFB_SEL = Low
OVP = 0 V
(Buck mode)
24
32
40
mV
—
VOVP
R1 = 470 kΩ, R2 = 30 kΩ
18
21
24
V
—
Fix off time at SW pin
0.5
1
2
μs
—
—
—
1.5
MHz
—
3.45
3.65
3.85
V
—
—
90
—
%
—
Over Voltage Protection (Boost Mode Only)
16
Over Voltage Protection
Threshold
Output Driver
17
Driver Off Time
TOFF
18
Maximum Operating Frequency
FMax
—
Regulator Voltage (VREG)
19
VREG Output Voltage
VREG
4 V ≤ VIN ≤ 20 V
No Load Condition,
CVREG = 1 μF
Efficiency
20
Efficiency
Eff
VIN = 6 V
1 LED of VF = 3.7 V
ILED = 400 mA
VFB_SEL = High
OVP = 0 V (Buck mode)
Ver. AEB
11
AN30888A
„ Control Pin Mode Table
Note) See parameters B No. 3, 4, 5, 6, 7 and 8 in the Electrical Characteristics for control voltage ranges.
Pin No.
Description
Pin voltage
Low
High
5
VFB_SEL
ON/OFF
VFB = 32 mV
VFB = 202 mV
12
PWM
ON/OFF
PWM OFF
PWM ON
14
ENB
ON/OFF
STANDBY
OPERATING
Ver. AEB
Remarks
Feedback voltage selection
When PWM is not used, the pin is left floating
Standby / Operating mode control
12
AN30888A
„ Electrical Characteristics Test Procedures
C
No.
Input
Parameter
Pin
No.
Output
Pin
No.
Conditions
Conditions
Switch
S1
S2
S3
S4
S5
S6
Circuit Current Consumption
1
2
Standby Current
14
12
5
8
6
11
ENB = 0 V
PWM = 0 V
VFB_SEL = 0 V
OVP = 0 V
CS = 0 V
SW = Hi-Z
4
Standby current
consumption
5
5
5
2
2
1
Operating Quiescent
Current
14
12
5
8
6
11
ENB = VIN
PWM = 0 V
VFB_SEL = 0 V
OVP = 0 V
CS = 0 V
SW = Hi-Z
4
Current consumption
2
5
5
2
2
1
ENABLE (ENB), VFB_SEL and PWM Control Function
3
4
5
6
7
ENB High Input Logic
14
12
5
8
6
11
ENB = 0.30 V
PWM = Hi-Z
VFB_SEL = 3.65 V
OVP = 0 V
CS = 0 V
SW = Hi-Z
16
Output DC voltage
3
1
2
2
2
1
ENB Low Input Logic
14
12
5
8
6
11
ENB = 3.0 V
PWM = Hi-Z
VFB_SEL = 3.65 V
OVP = 0 V
CS = 0 V
SW = Hi-Z
16
Output DC voltage
4
1
2
2
2
1
VFB_SEL High Input
Logic
14
12
5
8
6
11
ENB = VIN
PWM = Hi-Z
VFB_SEL = 0.70× VREG
OVP = 0 V
CS = 100 mV
SW = Hi-Z
11
Output DC voltage /
1 MHz
2
1
3
2
3
1
VFB_SEL Low Input
Logic
14
12
5
8
6
11
ENB = VIN
PWM = Hi-Z
VFB_SEL = 0.30 × VREG
OVP = 0 V
CS = 100 mV
SW = Hi-Z
11
Output DC voltage /
1 MHz
2
1
4
2
3
1
PWM High input Logic
14
12
5
8
6
11
ENB = VIN
PWM = 0.70 × VREG
VFB_SEL = 3.65 V
OVP = 0 V
CS = 0 V
SW = Hi-Z
11
Output DC voltage /
1 MHz
2
3
2
2
2
1
Ver. AEB
13
AN30888A
„ Electrical Characteristics Test Procedures (continued)
Input
C
No.
8
Parameter
Pin
No.
Output
Conditions
Switch
Pin
No.
Conditions
S1
S2
S3
S4
S5
S6
14
12
5
8
6
11
ENB = VIN
PWM = 0.30 × VREG
VFB_SEL = 3.65 V
OVP = 0 V
CS = 0 V
SW = Hi-Z
11
Output DC voltage /
1 MHz
2
4
2
2
2
1
14
12
5
8
6
11
ENB = VIN
PWM = Hi-Z
VFB_SEL = 0 V
OVP = 0 V
CS = 0 V
SW = Hi-Z
14
Current Consumption
2
1
5
2
2
1
SW High Output Logic
14
12
5
8
6
11
ENB = VIN
PWM = 3.65 V
VFB_SEL = 3.65 V
OVP = 0 V
CS = 0 V
SW = 0 A
11
Output DC voltage /
1 MHz
2
2
2
2
2
2
SW Low Output Logic
14
12
5
8
6
11
ENB = VIN
PWM = 0 V
VFB_SEL = 3.65 V
OVP = 0 V
CS = 0 V
SW = 0 A
11
Output DC voltage /
1 MHz
2
5
2
2
2
2
PWM Low input Logic
Input Pin Current Consumption
9
Enable Pin Current
Output Driver
10
11
Ver. AEB
14
AN30888A
„ Electrical Characteristics Test Procedures (continued)
C
No.
Input
Parameter
Pin
No.
Output
Conditions
Switch
Pin
No.
Conditions
S1
S2
S3
S4
S5
S6
Under voltage Lock Out (UVLO)
12
13
Under voltage protection
on value
14
12
5
8
6
11
ENB = VIN
PWM = Hi-Z
VFB_SEL = 3.65 V
OVP = 0 V
CS = 0 V
SW = Hi-Z
11
Output DC voltage /
1 MHz
2
1
2
2
2
1
Under voltage protection
Hysteresis
14
12
5
8
6
11
ENB = VIN
PWM = Hi-Z
VFB_SEL = 3.65 V
OVP = 0 V
CS = 0 V
SW = Hi-Z
11
Output DC voltage /
1 MHz
2
1
2
2
2
1
Ver. AEB
15
AN30888A
„ Technical Data
y I/O block circuit diagrams and pin function descriptions
Note) The characteristics listed below are reference values derived from the design of the IC and are not guaranteed.
Pin No.
Waveform and
voltage
Internal circuit
Impedance
1
GND
—
—
Signal Ground
2
—
—
—
No connection
3
—
—
—
No connection
4
DC
(3 V to 20 V)
—
Z : Low
Description
VIN
Power Supply of IC
VREG
16
5
DC
(0 V to 5 V)
VFB_SEL
5
VFB_SEL
200
Z : Hi-Z
Feedback voltage select pin
VREG
16
6
DC
(0 V to 250 mV)
CS
CS
6
Z : Hi-Z
500
Current Sense Pin
Ver. AEB
16
AN30888A
„ Technical Data (continued)
y I/O block circuit diagrams and pin function descriptions (continued)
Note) The characteristics listed below are reference values derived from the design of the IC and are not guaranteed.
Pin No.
Waveform and
voltage
Internal circuit
Impedance
7
—
—
—
Description
No connection
VREG
16
OVP
OVP
8
8
1k
DC
(0 V to 1.26 V)
Z : Hi-Z
1k
Over Voltage Protection input
pin for Boost and Buck-Boost
mode
Connect to GND for Buck
mode
9
GNDP
—
—
Power Ground
10
—
—
—
No connection
VREG
16
11
SW
11
Pulse
(0 V to 3.65 V)
VREG
SW
Z : Hi-Z
External NMOS Transistor
Gate Driving Pulse
VREG
167k
12
Pulse
(0 V to 5 V)
PWM
12
PWM
3k
Z : 170 kΩ
PWM Dimming Control
Ver. AEB
17
AN30888A
„ Technical Data (continued)
y I/O block circuit diagrams and pin function descriptions (continued)
Note) The characteristics listed below are reference values derived from the design of the IC and are not guaranteed.
Pin No.
Waveform and
voltage
Internal circuit
Impedance
13
—
—
—
Description
No connection
ENB
14
2k
14
DC
(3 V to 20 V)
ENB
200k
Z : 402 kΩ
Standby On/Off Control Pin
2k
200k
15
—
20k
—
—
No connection
VIN
4
16
VREG
DC
(Typ. 3.65 V)
Z : Hi-Z
Regulator Output Pin
VREG
16
550
550
550
Ver. AEB
18
AN30888A
(V
*)Nout
VIN
=
−
F
LEDs
„ Technical Data (continued)
Vout
)*(N
VIN
=
−
VF
LEDs
y Functions and properties descriptions
(1) Overview
AN30888A is a constant current LED driver. The IC works as a Boost /Buck-Boost/ Buck mode DCDC controller with external
MOSFET.
Operating input voltages ranges from 3 V to 20 V. The mode of operation depends on the number of LEDs to be driven and the supply
voltage level.
In general, please adhere to the following:
If total LED voltage drop is more than supply voltage, boost mode is adopted. If LED voltage drop is less than the supply voltage, buck
mode is adopted . If supply voltage is close to the total LED voltage drop, the Buck-Boost mode can be used. Please note that the
different mode of operation should be manually configured.
Output LED current can be designed ranges from 0 A and to a few amperes depending on the mode of operation, the external MOSFET
characteristic and feasible RCS value used. The control architecture uses current mode fix off time control. The VFB reference voltage
determines LED current by setting VFB_SEL pin with values of 32 mV or 202 mV under buck mode. By applying VFB voltage of 32
mV, user can achieve higher efficiency with lower power dissipation in RCS resistor. Applying 202 mV VFB voltage achieves better LED
current accuracy.
(2) Standby enable function
AN30888A enters standby mode when ENB pin is pulled low. During standby, the IC draws a small current of value less than 10 μA
from the power supply. This helps to achieve longer battery usage time. During Boost mode operation, although external MOSFET
cannot be turned on at standby condition, there is still a DC current path between the input and the LEDs through the inductor and
schottky diode. Thus it is important to make sure that during boost mode, the minimum forward voltage of the LED array must exceed
the maximum input voltage to ensure the LEDs remain off during standby mode.
Ver. AEB
19
AN30888A
(V
*)Nout
VIN
=
−
F
LEDs
„ Technical Data (continued)
Vout
)*(N
VIN
=
−
VF
LEDs
y Functions and properties descriptions (continued)
(3) Internal regulator
An internal 3.65 V regulator is used as the power supply for internal core circuit of this IC.
This regulated voltage, VREG will be provided when VIN is approximately in the range of 4 V to 20V. For VIN lower than 4 V, regulator
will act as a VIN voltage follower, with output voltage close to VIN. The amount of drop voltage from VIN during VIN follower mode
depends on load current of the regulator and also tolerance of the IC. In general, the regulator output voltage will be approximately 0.3 V
lower than VIN during this mode of operation.
This regulator requires a capacitor of 1 μF to be connected to VREG pin. This capacitor helps to provide a stable regulated voltage to the
IC. The regulator has a current ability of approximately 15 mA. However, it is not designed to provide as external power supply voltage.
Hence an external load exceeding approximately 0.5 mA to the VREG pin is not allowed.
(4) Output setting consideration
The output voltage, VOUT is set using the following equations for both boost and buck mode:
VOUT = (VF × NLEDs + VD) ………………………………………………
Eq[1]
(Boost mode)
VOUT = (VIN – VF × NLEDs) ……………………………………………… Eq[2]
(Buck mode)
VOUT = (VF × NLEDs + VD+VIN) …………………………………………
(Buck-Boost mode)
VIN :
VF :
NLEDs :
VD :
Eq[3]
Battery or Input power supply voltage
LED forward drop voltage
Number of LEDs stacked in series
Schottky diode forward drop voltage
For Boost mode or Buck-Boost mode operation, VOUT setting should be lesser than Drain–Source breakdown voltage of external
MOSFET as mention in (11). Also VOUT should be lesser than OVP protection threshold as mentioned in (9).
For Buck mode operation, VOUT setting should give sufficient voltage for external MOSFET to operate properly at the required output
current setting.
Ver. AEB
20
AN30888A
„ Technical Data (continued)
y Functions and properties descriptions (continued)
(5) Feedback voltage VFB at CS pin
The VFB voltage is generated internally in the IC and output at CS pin. This voltage allows users to fix the input peak current, IPK as well
as the LED output current, ILED. This voltage will change according to the setting at VFB_SEL pin.
For operation in boost mode/buck-boost mode, VFB will be inversely proportionally to supply voltage, VIN. When input supply voltage
decreases, VFB will increase. This ensure LED current remain accurate as supply voltage decreases.
When operating in buck mode, VFB voltage will remain at 202 mV or 32 mV depending on whether VFB_SEL pin is high or low.
The following are some figures of VFB voltage with respect to VIN. For detail information, please refer to graph and data table
information as the following.
For Boost mode and Buck-Boost mode :
VFB = 116 mV
(When VFB_SEL = High ; VIN = 6 V)
VFB = 50 mV
(When VFB_SEL = Low ; VIN = 6 V)
VFB = 198.3 mV (When VFB_SEL = High ; VIN = 3 V)
VFB = 88 mV
(When VFB_SEL = Low ; VIN = 3 V)
For Buck mode :
VFB = 202 mV
VFB = 32 mV
(When VFB_SEL = High, for all VIN level)
(When VFB_SEL = Low, for all VIN level)
To improve overall efficiency VFB voltage can be set lower by switching VFB_SEL = Low. On the other hand accuracy can be improved
by using VFB_SEL = High mode.
Ver. AEB
21
AN30888A
„ Technical Data (continued)
y Functions and properties descriptions (continued)
(5) Feedback voltage VFB at CS pin (continued)
Boost mode/
Buck-Boost mode
BOOST MODE: VCS Voltage vs VIN
VIN (V)
VFB_SEL
= High
VFB_SEL
= Low
VFB_SEL
= High
VFB_SEL
= Low
VFB (mV)
VFB (mV)
VFB (mV)
VFB (mV)
3
198.3
88.0
202
32
4
161.0
71.0
202
32
5
132.3
57.7
202
32
6
116.0
50.0
202
32
7
98.3
43.0
202
32
8
86.3
38.0
202
32
9
77.3
34.0
202
32
10
70.0
31.0
202
32
11
64.0
28.3
202
32
12
59.0
26.3
202
32
13
N.A
N.A
202
32
VFB_SEL="H"
14
N.A
N.A
202
32
VFB_SEL="L"
15
N.A
N.A
202
32
220.0
200.0
180.0
VCS(mV)
160.0
140.0
120.0
VFB_SEL="H"
100.0
VFB_SEL="L"
80.0
60.0
40.0
20.0
0.0
3
5
7
9
11
VIN(V)
VCS(mV)
BUCK MODE: VCS Voltage vs VIN
220.0
200.0
180.0
160.0
140.0
120.0
100.0
80.0
60.0
40.0
20.0
0.0
3
5
7
9
11
13
Buck mode
15
VIN(V)
Ver. AEB
22
AN30888A
PKFB
2
*
-L
Eq[7]
IV
CS
=
R
„ Technical Data (continued)
=
IR
CS
-PK
y Functions and properties descriptions (continued)
(6) Inductor selection
Inductor value, L is set by the required inductor ripple current desired.
The general trend for lower inductor value is a smaller inductor physical size, but a larger input ripple current. Similarly, an increase in
inductor value will decease input ripple current.
Users are advice to choose an inductor that can handle the peak current IPK, flowing across it without saturating. In addition, inductor
with lower series resistance are preferred to provide better operating efficiency.
The following equation gives a general guideline in selection inductor value based on 30% peak to peak ripple current across the
inductor.
(VOUT – VIN) × TOFF
L = ————————————— ………………………
0.3 × IIN
Eq[4]
(Boost mode，Buck-Boost mode)
(VIN – VOUT) × TOFF
L = ————————————— ………………………
0.3 × ILED
Eq[5]
(Buck mode)
VOUT = Output voltage
VIN = Input supply voltage
TOFF = Fixed off time design at 1 μs
ILED = LED output current
IINは，IIN is input current from supply voltage
Please note that the 0.3 factor can be altered if 30% peak to peak current is changed.
i.e, if percentage of peak to peak current needed is 40%, this factor will be 0.4.
Ver. AEB
23
AN30888A
*2PFB
-L
Eq[7]
IV
CS
=
R
K
„ Technical Data (continued)
-PK
=
IR
CS
y Functions and properties descriptions (continued)
(7) Setting output LED current and choosing current sense resistor RCS
The LED current in this IC can be set easily by selecting the appropriate RCS resistor to be used at CS pin of this chip.
For Boost Mode and Buck-Boost mode :
RCS resistor can be set in the following way :
First is to calculate input current IIN at the required operating condition :
IIN = (VOUT + VD) × (ILED / VIN) …………………………… Eq[6]
(Boost mode，Buck-Boost mode)
VOUT = Output voltage
VD = Schottky diode forward drop voltage
ILED = Required LED current
VIN = Input supply voltage
After which the peak input current, IPK can be determine by adding IIN with half the peak to peak ripple current at the inductor.
(VOUT – VIN) × TOFF
IPK = IIN + ——————————— …………………… Eq[7]
2L
(Boost mode，Buck-Boost mode)
TOFF = TOFF is fixed off time = 1 μs
L = Inductor value found in part (6) inductor selection
VOUT = Output voltage
VIN = Input supply voltage
IIN = IIN is input current found in Eq[6]
Lastly, RCS resistor can be determine by using :
VFB
RCS = ——— ………………………………………………
IPK
Eq[8]
(Boost mode，Buck-Boost mode)
VFB is voltage at CS pin. Refer to data graphs for the VFB voltage at different input voltage condition.
IPK is peak current found in Eq[7]
Using numeric example of operating condition :
VIN = 6 V, VOUT = 10 V, ILED = 500 mA, TOFF = 1 μs, L = 16 μH, VD = 0.4 V, VFB = 0.1 V@VIN = 6 V
From Eq[6] :
From Eq[7] :
From Eq[8] :
IIN = (10 + 0.4) × (0.5 / 6) = 0.8667 A
(10 – 6) × 1μ
IPK = 0.8667 + ——————— = 0.9971 A
2 × 16μ
0.1
RCS = ———— = 100.8 mΩ
0.9917
Ver. AEB
24
AN30888A
„ Technical Data (continued)
y Functions and properties descriptions (continued)
(7) Setting output LED current and choosing current sense resistor RCS (continued)
For Buck Mode :
RCS resistor can be set in the following way :
First is to calculate the peak current IPK using Eq[9]. During buck mode, peak current sense correspond to the average output LED
current plus half of actual current ripple through the inductor.
(VIN – VOUT) × TOFF
IPK = ILED + ——————————— …………………… Eq[9]
2L
(Buck mode)
VOUT = Output voltage
VIN = Input supply voltage
TOFF = TOFF = Fixed off time design at 1 μs
ILED = LED output current
L = Inductor value found in part (6) inductor selection
Lastly, RCS resistor can be determine by using :
VFB
RCS = ——— ………………………………………………
IPK
Eq[10]
(Buck mode)
VFB is voltage at CS pin. Refer to data graphs for the VFB voltage at different input voltage condition.
IPK is peak current found in Eq[9] .
Using numeric example of operating condition :
VIN = 12 V, VOUT = 2 V, ILED = 500 mA, TOFF = 1 μs, L = 66 μH, VFB = 0.2 V
(12 – 2) × 1μ
IPK = 0.5 + —————— = 0.575 A
2 × 66μ
0.2
From Eq[10] : RCS = ———— = 348 mΩ
0.575
From Eq[9] :
Please note that for component deviation such as inductor, diodes, etc, these deviation can cause the designed IPK to be higher or lower
than the calculated value.
Users may need to fine tune the value of RCS from the calculated values in order to obtain accurate ILED measurement.
Please take note of total impedance including parasitic impedance of PCB trace at CS pin to ground when designing the required RCS
value. This is especially important if the designed ILED is high as RCS value will be small and in turn making parasitic impedance
significant to the total impedance seen at CS pin
Ver. AEB
25
AN30888A
„ Technical Data (continued)
y Functions and properties descriptions (continued)
(8) Soft start
Soft start circuit is incorporated into this IC to avoid high in-rush current during start-up.
After the device is enabled (ENB = High), the output inductor current and output voltage will rise slowly from initial condition. This
slow start-up time ensure smooth start-up as well as minimize in-rush current.
(9) Over Voltage Protection (OVP)
When operating in Boost mode or Buck-Boost mode, over voltage protection is needed to prevent damages to IC or external component
damages in cases of open LED condition.
OVP switches off external power MOSFET to prevent output from rising over a designed OVP voltage. Output voltage should be
limited to the rating of external component used. (for example Drain Source voltage rating of the external MOSFET or the output
capacitor)
OVP compares the internal reference voltage of 1.26 V with output voltage through resistor network.
OVP threshold is set using the following equation:
1.262 V × (R1 ＋R2)
VOVP = —————————— ……………………
R2
Eq[11]
(Boost mode，Buck-Boost mode)
If R1 = 470 kΩ, R2 = 30 kΩ, OVP threshold will be designed at around 21 V.
When OVP is triggered, output voltage will be clamped at this threshold voltage (with hysteresis of around 1 V to 2 V) until the fault
(e.g open LED condition) has been removed.
When operating in buck mode, the OVP pin must be short to ground to disable this function as OVP function is not necessary in this
mode.
Ver. AEB
26
AN30888A
„ Technical Data (continued)
y Functions and properties descriptions (continued)
(10) Under Voltage Lock Out (UVLO)
Under Voltage lock out prevents IC from operation at supply voltage lower than 2.1 V.
This function prevent IC from abnormal operation when supply voltage VIN drops below our recommended input range. When input
voltage is lower than this lock out value of 2.1 V, external MOSFET will be switched off. When input voltage rises to 2.4 V or more,
device operation starts again. This means a hysteresis voltage of about 0.3 V.
(11) Power MOSFET consideration
When selecting the power MOSFET, it is important to consider parameters such as gate-source, drain-source breakdown voltage, total
gate capacitance, ON resistance and the drain current rating.
When power is turned on for IC operating in boost mode, output voltage needed to drive LED will be reflected to Drain-Source voltage
of the power MOSFET. Thus it is recommended to select a MOSFET that can handle this output voltage. Alternatively, output and
Drain-Source voltage can be protected and clamped by OVP circuit as mentioned in point (9).
Gate capacitance of the MOSFET chosen should ideally to be smaller than 3 nF.
(12) PWM operation
PWM signal can be generated externally and input into PWM pin of this IC. This PWM signal will turn on and off the output driver,
giving an average output LED current that is proportional to the duty cycle of the PWM signal.
ILED(avg.) = ILED × Duty………………………………………
Eq[12]
(Boost / Buck-Boost / Buck mode)
ILED(avg.) = The average output LED current after PWM is input
ILED = The nominal LED current set in part (7)
Duty = The ratio of on pulse time compared to total period time of the PWM signal.
A PWM frequency of 1 kHz or lower is recommended to minimize error due to rise and fall time of the converter output.
Ver. AEB
27
AN30888A
„ Technical Data (continued)
y Functions and properties descriptions (continued)
(13) Maximum duty operation
Maximum Duty limitation is needed when operating in Boost or Buck- Boost mode. This prevents the output voltage from having
abnormal operation. For Buck mode, there is no need for maximum duty limit as SW pin is able to switch to 100% duty.
Please refer to the graph below for maximum duty vs VIN data for Boost and Buck-Boost mode operation.
Boost/Buck-boost mode
VIN (V)
Duty Limit (%)
3.0
88.73
3.5
87.09
4.0
85.27
4.5
83.58
5.0
81.99
5.5
79.79
6.0
78.40
6.5
77.38
7.0
76.25
7.5
75.19
8.0
73.92
8.5
72.89
9.0
71.78
9.5
70.83
10.0
69.91
10.5
68.90
11.0
67.97
11.5
67.09
12.0
66.33
(14) Minimum duty operation
Parasitic circuit capacitance, inductance and external MOSFET gate drive current can create spike in the current sense, CS pin voltage at
the point when external MOSFET is switched on. In order to prevent this spike to terminate the ON time prematurely, an internal filter
of time constant, 100 ns is designed in chip. This time constant of 100 ns translates to a minimum duty of around 9% for all modes of
operation. To further reduce the spike in the CS voltage especially when operating in low ILED condition (example: RCS is more than 0.8
Ω or more), external RC filter can be used in between VFB node to CS pin which act as a low pass filter to filter spike noise from
entering CS pin. This RC filter time constant should be long enough to reduce the parasitic spike without significantly affecting the
shape of CS voltage.
The recommended RC value range from : R = 10 Ω to 1 kΩ and C = 100 pF to 500 pF depending on mode of operation and spike level.
Ver. AEB
28
AN30888A
„ Technical Data (continued)
y PD ⎯ Ta diagram
Ver. AEB
29
AN30888A
„ Usage Notes
y Special attention and precaution in using
1. This IC is intended to be used for general electronic equipment [LED Lighting Devices].
Consult our sales staff in advance for information on the following applications:
x Special applications in which exceptional quality and reliability are required, or if the failure or malfunction of this IC may
directly jeopardize life or harm the human body.
x Any applications other than the standard applications intended.
(1) Space appliance (such as artificial satellite, and rocket)
(2) Traffic control equipment (such as for automobile, airplane, train, and ship)
(3) Medical equipment for life support
(4) Submarine transponder
(5) Control equipment for power plant
(6) Disaster prevention and security device
(7) Weapon
(8) Others : Applications of which reliability equivalent to (1) to (7) is required
It is to be understood that our company shall not be held responsible for any damage incurred as a result of or in connection with
your using the IC described in this book for any special application, unless our company agrees to your using the IC in this book
for any special application.
2. Pay attention to the direction of LSI. When mounting it in the wrong direction onto the PCB (printed-circuit-board), it might
smoke or ignite.
3. Pay attention in the PCB (printed-circuit-board) pattern layout in order to prevent damage due to short circuit between pins. In
addition, refer to the Pin Description for the pin configuration.
4. Perform a visual inspection on the PCB before applying power, otherwise damage might happen due to problems such as a solderbridge between the pins of the semiconductor device. Also, perform a full technical verification on the assembly quality, because
the same damage possibly can happen due to conductive substances, such as solder ball, that adhere to the LSI during
transportation.
5. Take notice in the use of this product that it might break or occasionally smoke when an abnormal state occurs such as output pinVCC short (Power supply fault), output pin-GND short (Ground fault), or output-to-output-pin short (load short) .
And, safety measures such as an installation of fuses are recommended because the extent of the above-mentioned damage and
smoke emission will depend on the current capability of the power supply.
6. When designing your equipment, comply with the range of absolute maximum rating and the guaranteed operating conditions
(operating power supply voltage and operating environment etc.). Especially, please be careful not to exceed the range of absolute
maximum rating on the transient state, such as power-on, power-off and mode-switching. Otherwise, we will not be liable for any
defect which may arise later in your equipment.
Even when the products are used within the guaranteed values, take into the consideration of incidence of break down and failure
mode, possible to occur to semiconductor products. Measures on the systems such as redundant design, arresting the spread of fire
or preventing glitch are recommended in order to prevent physical injury, fire, social damages, for example, by using the products.
7. When using the LSI for new models, verify the safety including the long-term reliability for each product.
8. When the application system is designed by using this LSI, be sure to confirm notes in this book.
Be sure to read the notes to descriptions and the usage notes in the book.
Ver. AEB
30
Request for your special attention and precautions in using the technical information and
semiconductors described in this book
(1) If any of the products or technical information described in this book is to be exported or provided to non-residents, the laws and
regulations of the exporting country, especially, those with regard to security export control, must be observed.
(2) The technical information described in this book is intended only to show the main characteristics and application circuit examples
of the products. No license is granted in and to any intellectual property right or other right owned by Panasonic Corporation or any
other company. Therefore, no responsibility is assumed by our company as to the infringement upon any such right owned by any
other company which may arise as a result of the use of technical information described in this book.
(3) The products described in this book are intended to be used for general applications (such as office equipment, communications
equipment, measuring instruments and household appliances), or for specific applications as expressly stated in this book.
Consult our sales staff in advance for information on the following applications:
– Special applications (such as for airplanes, aerospace, automotive equipment, traffic signaling equipment, combustion equipment,
life support systems and safety devices) in which exceptional quality and reliability are required, or if the failure or malfunction of
the products may directly jeopardize life or harm the human body.
It is to be understood that our company shall not be held responsible for any damage incurred as a result of or in connection with
your using the products described in this book for any special application, unless our company agrees to your using the products in
this book for any special application.
(4) The products and product specifications described in this book are subject to change without notice for modification and/or improvement. At the final stage of your design, purchasing, or use of the products, therefore, ask for the most up-to-date Product
Standards in advance to make sure that the latest specifications satisfy your requirements.
(5) When designing your equipment, comply with the range of absolute maximum rating and the guaranteed operating conditions
(operating power supply voltage and operating environment etc.). Especially, please be careful not to exceed the range of absolute
maximum rating on the transient state, such as power-on, power-off and mode-switching. Otherwise, we will not be liable for any
defect which may arise later in your equipment.
Even when the products are used within the guaranteed values, take into the consideration of incidence of break down and failure
mode, possible to occur to semiconductor products. Measures on the systems such as redundant design, arresting the spread of fire
or preventing glitch are recommended in order to prevent physical injury, fire, social damages, for example, by using the products.
(6) Comply with the instructions for use in order to prevent breakdown and characteristics change due to external factors (ESD, EOS,
thermal stress and mechanical stress) at the time of handling, mounting or at customer's process. When using products for which
damp-proof packing is required, satisfy the conditions, such as shelf life and the elapsed time since first opening the packages.
(7) This book may be not reprinted or reproduced whether wholly or partially, without the prior written permission of our company.
20100202
Request for your special attention and precautions in using the technical information and
semiconductors described in this book
(1) If any of the products or technical information described in this book is to be exported or provided to non-residents, the laws and
regulations of the exporting country, especially, those with regard to security export control, must be observed.
(2) The technical information described in this book is intended only to show the main characteristics and application circuit examples
of the products. No license is granted in and to any intellectual property right or other right owned by Panasonic Corporation or any
other company. Therefore, no responsibility is assumed by our company as to the infringement upon any such right owned by any
other company which may arise as a result of the use of technical information described in this book.
(3) The products described in this book are intended to be used for general applications (such as office equipment, communications
equipment, measuring instruments and household appliances), or for specific applications as expressly stated in this book.
Consult our sales staff in advance for information on the following applications:
– Special applications (such as for airplanes, aerospace, automotive equipment, traffic signaling equipment, combustion equipment,
life support systems and safety devices) in which exceptional quality and reliability are required, or if the failure or malfunction of
the products may directly jeopardize life or harm the human body.
It is to be understood that our company shall not be held responsible for any damage incurred as a result of or in connection with
your using the products described in this book for any special application, unless our company agrees to your using the products in
this book for any special application.
(4) The products and product specifications described in this book are subject to change without notice for modification and/or improvement. At the final stage of your design, purchasing, or use of the products, therefore, ask for the most up-to-date Product
Standards in advance to make sure that the latest specifications satisfy your requirements.
(5) When designing your equipment, comply with the range of absolute maximum rating and the guaranteed operating conditions
(operating power supply voltage and operating environment etc.). Especially, please be careful not to exceed the range of absolute
maximum rating on the transient state, such as power-on, power-off and mode-switching. Otherwise, we will not be liable for any
defect which may arise later in your equipment.
Even when the products are used within the guaranteed values, take into the consideration of incidence of break down and failure
mode, possible to occur to semiconductor products. Measures on the systems such as redundant design, arresting the spread of fire
or preventing glitch are recommended in order to prevent physical injury, fire, social damages, for example, by using the products.
(6) Comply with the instructions for use in order to prevent breakdown and characteristics change due to external factors (ESD, EOS,
thermal stress and mechanical stress) at the time of handling, mounting or at customer's process. When using products for which
damp-proof packing is required, satisfy the conditions, such as shelf life and the elapsed time since first opening the packages.
(7) This book may be not reprinted or reproduced whether wholly or partially, without the prior written permission of our company.
20100202