KEC KAB3405T_08

SEMICONDUCTOR
KAB3405T
TECHNICAL DATA
BICD LINEAR INTEGRATED CIRCUIT
Step Up Type DC/DC Converter for White LED
KAB3405T is a high efficient Step-Up Type DC/DC Converter specially
designed for constant current drive of White LED. This IC can drive 2-10
white LEDs connected series using a Li-ion Battery. This IC contains N-ch
MOS-FET Transistor for Coil-Switching, and LED Current (IF) is set with an
external resistor.
Features
Variable LED Current IF is set with a external resistor
: 20 mA (Typ.) @ RSENS = 15
High Efficiency
Output Over Voltage Shutdown
Built in output over voltage protect circuit.
Switching Frequency : 1.0 MHz (Typ.)
Applications
Back light white LEDs in LCD of PDA, Cellular Phone
Handy Terminal Equipment.
Basic Application Circuit
2008. 3. 10
Revision No : 2
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KAB3405T
Block Diagram
Pin Function
Pin No.
Symbol
1
SHDN
2
OVD
3
VIN
Supply Voltage Input Terminal. ( 2.8V to 5.5V)
4
SW
Switch Terminal for DC/DC Converter. Nch MOSFET Built-In.
5
GND
6
FB
2008. 3. 10
Function Description
Voltage-Input Terminal for IC-Enable / Disable.
Over Voltage Detection Terminal. IC Switching Operation is disabled with detection over voltage. If the voltage returns
to detection level or less, Operation is enabled again.
Ground Terminal.
LED IF Setting Resister Connecting Terminal.
Revision No : 2
2/6
KAB3405T
MAXIMUM RATINGS (Ta = 25 C if without notice)
Characteristics
Symbol
Ratings
Unit
VIN
-0.3 to +6.0
V
VIN(SHDN)
-0.3 to +VIN + 0.3
V
Switching Terminal Voltage
VO (SW)
-0.3 to 40
V
Switching Terminal Current
IO (SW)
1500
mA
Power Supply Voltage
Input Voltage
0.41 (Device)
PD
Power Dissipation
W
0.47(on PCB)Caution 2
300(Device)
Rth(j-a)
Thermal Resistance
/W
260(on PCB)
Operation Temperature Range
Topr
-40 to +85
Storage Temperature Range
Tstg
-55 to +150
Tj
150
Maximum Junction Temperature
Caution 2: Power Dissipation must be calculated with subtraction of 3.8 mW/ C from Maximum
Rating with every 1
if Topr is upper 25 C. (on PCB)
ELECTRICAL CHARACTERISTICS (Ta = 25 , VIN=2.8V to 5.5V if without notice)
Characteristics
Input Voltage Range
Symbol
Test Condition
Min
Typ
Max
Unit
VIN
-
2.8
-
5.5
V
mA
Operating Consumption Current
IN(ON)
VIN=3.6V, RSENS=15
-
0.6
0.9
Quiescent Consumption Current
IN(Off)
VIN=3.6V,VSHDN=0V
-
0.5
1.0
VSHDNH
-
1.3
-
VIN
V
SHDN Terminal ’L’ Level Input Voltage VSHDNL
-
0
-
0.4
V
-
0
1.0
0.77
1.0
1.43
-
0.5
1
VIN=3.6V, RSENS=15 , Ta=25 C, L=22 H
285
300
315
mV
VIN=4.2V, RSENS=15 , Ta=25 C, L=22 H
285
300
315
mV
%
SHDNTerminal ’H’ Level Input Voltage
SHDN Terminal Current
ISHDN
VIN=3.6V,VSHDN=3.6V or 0V
Integrated MOS-Tr Switching requency
fOSC
VIN=3.6V,VSHDN=3.6V
Switching Terminal Leak Current
FB Terminal Feedback Voltage (VFB)
IOZ(SW)
VFB
-
FB Terminal Line Regulation
VFB
VIN=3.6V center VIN=3.0 to 5.0V
-5
-
5
FB Terminal Current
IFB
VIN=3.6V, VSHDN=3.6V, VFB=300mV
-
0.02
-
35
38
39.5
-
0.5
1
OVD terminal Voltage
VOVD
OVD Terminal Leakage Current
IOVD
2008. 3. 10
Revision No : 2
VOVD=30V
MHz
V
3/6
KAB3405T
Protection in LED opened condition
The operation with OVD terminal is available for the protection in case LED Circuit opened.
When the voltage of OVD terminal is over 38V (typ.), Nch MOS switching operation is disabled in the IC. When the voltage of
OVD terminal drops below 38V (typ.), Nch MOS switching operation becomes available again.
If load of LED is detached, Nch MOS switching operation is disabled with detection of boost circuit voltage and the IC is
protected from unexpected over voltage.
Setting of external Capacitor
recommended values are
CIN = Over 2.2 ( F), COUT = Over 1.0 ( F)
The recommended values of the capacitors depend on the control of brightness. For details, please see the item Control of
brightness from the next page.)
These recommended values reduce fluctuation of input current to up accuracy of brightness.
<Please see after page-6>
The capacitor value must be considered for gain enough accuracy of brightness with reduction of noise from
Input current changing.
Setting of External Inductor Size
Please select the inductor size with referring this table corresponding to each number of LEDs.
Recommendation for the case that LED current IF = 20 mA
LEDs
Inductor Size
Note
2-5
Over 6
10 H
22 H
LED current IF = 20 mA
Setting of IF
Resistance connects between RSENS pin and GND.
The average current is set by this RSENS value and average current are obtained by the following equation.
IF[mA] =
Current Value error is within
2008. 3. 10
300[mV]
RSENS[ ]
5%.
Revision No : 2
4/6
KAB3405T
Current Dimming Control
Recommended Brightness Control Circuits are 3 types.
1) Input analog voltage to FB terminal
IF can be adjusted with Analog voltage input to FB terminal.
This method is without repeating IC ON/OFF, and no consider holding rash current.
[Notice]
LED current value goes ever 100% of current set with RSENS, if the input voltage is
between 0 V to 300 mV(typ)
<<Recommended application>>
2) Input PWM signal with filtering to FB terminal
IF can be adjusted with filtering PWM signal using RC filter indicated in recommended circuit, because the PWM signal can be
regard as analog voltage after filtering.
This method is without repeating IC ON/OFF, and no need to consider holding rash current.
[Notice]
LED current value goes over 100% of the current set with RSENS, if the input voltage after filtering
is between 0 V to 300 mV (typ).
<<Recommended application>>
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Revision No : 2
5/6
KAB3405T
3) Input Logic signal
IF can be adjusted with Logic signal input as indicated in recommended circuit.
The resistor connected the ON-state Nch MOS Drain and RSENS determines IF.
Average of setting current Io (mA) is next, approximately.
IF=(300 [mV]/Sum of resistor value [ ])
IF [mA] =
300[mV]
Sum of resistor v alue [ ]
<<Recommended application>>
M1
M2
LED Current
OFF
OFF
300[mV]
RSENS[ ]
ON
OFF
300[mV]
RSENS[ ] R1[ ]
RSENS[ ]+ R1[ ]
OFF
ON
300[mV]
RSENS[ ] R2[ ]
RSENS[ ]+ R2[ ]
ON
ON
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300[mV]
Revision No : 2
RSENS[
RSENS[ ] R1[ ] R2[ ]
] R1[ ] + RSENS[ ] R2[ ] + R1[ ] R2[
]
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