TB62731FUG
TOSHIBA BiCD Digital Integrated Circuit Silicon Monolithic
TB62731FUG
Step-up DC-DC Converter for White LED Driver
The TB62731FUG is an LED driver that uses a high power
efficiency step-up DC-DC converter. The converter turns on/off 2
to 6 white LEDs in series.
The IC incorporates an N-channel MOSFET transistor used for
coil-switching and a function that reduces the LED current in
response to increase in temperature.
The mean LED current can be easily set using an external
resistor.
The IC is ideal as a driver for LED light sources used as liquid
crystal backlights for PDAs, cellular phones, and handy
terminals.
The suffix (G) appended to the part number represents a Lead
(Pb) -Free product.
Weight: 0.016 g (typ.)
Features
•
•
Maximum output voltage: Vo
≤
28 V
Mean LED current values set according to external resistor
14 mA (typ.) @R_sens = 2.7
Ω
20 mA (typ.) @R_sens = 1.8
Ω
•
•
•
•
Supply power: Up to 320 mW supported
Compact package: SSOP6-P-0.95B, 6 pins
Built-in temperature derating function: LED current derated automatically depending on temperature
High power efficiency
Up to 80% of peak power efficiency achieved using recommended components
Ron = 2.0
Ω
(typ.) @V
IN
= 3.2~5.5 V
Built-in low Ron power MOS switch
Pin assignment
(top view)
K
A
GND
GND
SHDN
V
CC
1
2006-06-14
TB62731FUG
Block Diagram
V
CC
A
OSC
350 kHz
S
R
Q
Buffer
SHDN
STB
0.12 V
0.5
Ω
REF
i (add)
i (sub)
A
K
GND
GND
Pin Functions
No
1
2, 5
3
4
6
Symbol
K
GND
SHDN
V
CC
A
Function
Pin connecting LED cathode to resistor used to set current.
Feedback pin for voltage waveforms for controlling the LED constant current.
Ground pin for the logic
IC enable pin.
Low, Standby Mode takes effect and pin A is turned off.
Input pin for power supply for operating the IC.
Operating voltage range: 3.0~5.5 V
DC-DC converter switch pin.
The switch is an N-channel MOSFET transistor.
Note: Connect both GND pins to ground.
2
2006-06-14
TB62731FUG
Absolute Maximum Ratings
(unless otherwise specified, T
opr
=
25°C)
Characteristics
Supply voltage
Input voltage
Pin A (anode) current
Pin A voltage
Symbol
V
CC
V
IN
I
o
(A)
V
o
(A)
P
D
R
th (j-a)
1
R
th (j-a)
2
Operating temperature range
Storage temperature range
Maximum junction temperature
T
opr
T
stg
T
j
Rating
−0.3~+6.0
−0.3~+V
CC
+
0.3
+270
−0.3~+28
0.41 (IC only)
Power dissipation
0.47 (IC mounted on PCB)
(Note)
300 (IC only)
260 (IC mounted on PCB)
−40~+85
−40~+150
125
°C
°C
°C
W
Unit
V
V
mA
V
Saturation thermal resistance
°C/W
Note: The power dissipation is derated by 3.8 mW/°C from the Absolute maximum rating for every 1°C exceeding
the ambient temperature of 25°C (when the IC is mounted on a PCB).
Recommended Operating Conditions (unless otherwise specified,
T
opr
= −40~85°C)
Characteristics
Supply voltage
SHDN pin high-level input voltage
SHDN pin low-level input voltage
SHDN pin high-level input pulse width
Set LED current (mean)
Symbol
V
CC
V
IH
V
IL
tpw SHDN
I
o
Test
circuit
⎯
⎯
⎯
⎯
⎯
Test condition
⎯
⎯
⎯
⎯
V
o
(A)
=
V
IN
3.0 V, V
OUT
16 V
Min
3.0
V
CC
−
0.5
0
500
5
Typ.
⎯
⎯
⎯
⎯
⎯
Max
4.3
V
CC
0.5
⎯
20
Unit
V
V
V
µs
mA
3
2006-06-14
TB62731FUG
Electrical Characteristics (unless otherwise specified,
Ta
= −40~85°C,
V
CC
=
3.0~5.5 V)
Characteristics
Supply voltage
Current consumption at operation
Current consumption at standby
SHDN pin current
Internal MOS transistor on-resistance
Internal MOS transistor switching
frequency
Pin A voltage
Pin A current
Pin A leakage current
Set LED current (mean)
Pin K derating start ambient
temperature
Symbol
V
CC
I
CC
(ON)
I
CC
(SHDN)
I_SHDN
Ron
f
OSC
V
o
(A)
I
o
(A)
I
oz
(A)
I
o
Test
circuit
⎯
⎯
⎯
⎯
⎯
⎯
⎯
⎯
⎯
⎯
⎯
V
CC
=
3.6 V
SHDN
=
0 V
SHDN
=
V
CC
,
Built-in pull-down resistor
I (A)
<
270 mA,
=
Including detected resistance
⎯
⎯
⎯
⎯
V
CC
=
3.2~4.2 V,
R_sens
=
1.8
Ω
T
opr
=
25°C
Test condition
⎯
Min
3.0
⎯
⎯
⎯
⎯
275
28
210
⎯
17.6
(Note 1)
⎯
45
(Note 2)
⎯
°C
Typ.
⎯
0.6
0.5
4.2
2.0
350
⎯
240
0.5
20
Max
5.5
0.9
1.0
7
2.5
425
⎯
270
1
22.4
Unit
V
mA
µA
µA
Ω
kHz
V
mA
µA
mA
Tdel
Equivalent to R_sens
=
1.8
Ω,
L
=
4.7
µH,
V
O
=
16 V
Note 1: Due to operation of the temperature derating function, measure when Ta
=
25°C.
Note that fluctuation in R_sens resistors is not included in the specified value.
I
o
may be different from the specified value due to the relation between the inductor value and load.
Note 2: This rating is guaranteed by the design.
4
2006-06-14
TB62731FUG
IL, ILpeak
V
CC
A
OSC
350 kHz
SHDN
V
IN
C1
STB
S
R
Q
Buffer
NMOS
C2
Ic2
0.12 V
0.5
Ω
I
o
K
REF
i (add)
i (sub)
A
R_sens
GND
Figure 1
Application Circuit
The basic TB62731FUG circuit uses a step-up DC-DC converter and burst control of the current pulse.
Basic Operation
The internal MOS transistor (NMOS) is turned on at f
OSC
=
350 kHz, charging energy to the inductor.
The inductance current IL increases from 0. When IL
=
ILpeak
=
240 mA (typ.) or when 5/6 (83.3%) of f
OSC
(=
350 kHz) is reached, the transistor is turned off.
At that time, the coil maintains IL
=
ILpeak, the Schottky diode is turned on, and IL
=
Ic2 flows. Then, Ic2
decreases, reaching IL
=
0.
The above operation repeats. When Ic2 is fully charged, the surplus current becomes I
o
, which flows to the
LED.
The graph below shows details of the basic pulse used for burst control.
IL, ILpeak
Maximum duty: 83.3% of f
OSC
ILpeak
=
240 mA (typ.)
With low inductance
With high inductance
T
=
1/f
OSC
, f
OSC
=
350 kHz (typ.)
Figure 2 Switching Waveform of Inductance
5
2006-06-14
Microcontroller MCU
京公网安备 11010802033920号
EEWORLD
