AS1109-BSOU austriamicrosystems, AS1109-BSOU Datasheet - Page 19

• Manufacturer Part Number: AS1109-BSOU
• Description: IC DRIVER LED 4-BIT CC 16-SOIC
• Manufacturer: austriamicrosystems
• Type: General Purposer

Specifications of AS1109-BSOU

• Constant Current: Yes
• Topology: 8-Bit Shift Register, PWM
• Number Of Outputs: 8
• Internal Driver: Yes
• Type - Primary: General Purpose
• Frequency: 50MHz
• Voltage - Supply: 3 V ~ 5.5 V
• Voltage - Output: 15V
• Mounting Type: Surface Mount
• Package / Case: 16-SOIC (3.9mm Width)
• Operating Temperature: -40°C ~ 85°C
• Current - Output / Channel: 100mA
• Internal Switch(s): Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Efficiency: -

AS1109
Datasheet - A p p l i c a t i o n I n f o r m a t i o n
Constant Current
In LED display applications, the AS1109 provides virtually no current variations from channel-to-channel and from AS1109-to-AS1109. This is
mostly due to 2 factors:
Adjusting Output Current
The AS1109 scales up the reference current (I
Figure 3 on page 7
I
Where:
R
V
The magnitude of current (as a function of R
shows the relationship curve between the I
Package Power Dissipation
The maximum allowable package power dissipation (PD) is determined as:
When 8 output channels are turned on simultaneously, the actual package power dissipation is:
Therefore, to keep P
Where:
T
Delayed Outputs
The AS1109 has graduated delay circuits between outputs. These delay circuits can be found between OUTNn and constant current block.
The fixed delay time is 20 ns (typ) where OUTN0 has no delay, OUTN1 has 20ns delay, OUTN2 has 40ns delay ... OUTN7 has 140ns delay. This
delay prevents large inrush currents, which reduce power supply bypass capacitor requirements when the outputs turn on
page 10)
Switching-Noise Reduction
LED drivers are frequently used in switch-mode applications which normally exhibit switching noise due to parasitic inductance on the PCB.
Load Supply Voltage
Considering the package power dissipation limits (see EQ 4:6), the AS1109 should be operated within the range of
V
For example, if V
supply voltage or a voltage reducer (V
V
Note: Resistors or zener diodes can be used as a voltage reducer as shown in
www.austriamicrosystems.com/LED-Driver-ICs/AS1109
OUT TARGET
J
EXT
REXT
DS
DS
= 150ºC
While I
In the saturation region, the characteristics curve of the output stage is flat
constant regardless of the variations of LED forward voltages (V
= 0.4 to 1.0V.
= (V
is the resistance of the external resistor connected to pin REXT.
is the voltage on pin REXT.
LED
OUT
-V
can be calculated by:
F
≥ 50mA, the maximum current skew is less than ±2% between channels and less than ±2% between AS1109 devices.
LED
) - V
the output current in the saturation region is extremely flat so that it is possible to define it as target current (I
D(ACT)
is higher than 5V, V
DROP
I
REF
.
≤ P
D(MAX)
= V
REXT
I
DROP
OUT
, the allowable maximum output current as a function of duty cycle is:
DS
I
/R
OUT TARGET
OUT TARGET
P
= {[(T
EXT
) should be used. The voltage reducer allows
may be so high that P
D(ACT)
EXT
REF
) is around 100mA at 186Ω, 50.52mA at 372Ω and 25.26mA at 744Ω.
(if the other end of R
J
) set by external resistor (R
P
-T
D(MAX)
= (I
AMB
of each channel and the corresponding external resistor (R
DD
= I
V
)/R
REXT
*V
REF
= (T
TH(J-A)
DD
*15 = (1.253V/R
J
) + (I
= 1.253V
D(ACT)
-T
Revision 1.20
F
AMB
]-(I
).
OUT
DD
)/R
> P
EXT
*V
*Duty*V
EXT
TH(J-A)
D(MAX)
DD
(see Figure 5 on page
is connected to ground)
) to sink a current (I
)}/V
Figure
EXT
DS
where V
DS
)*15
*8)
/Duty/8
24.
DS
= V
LED
OUT
7). Thus, the output current can be kept
) at each output port. As shown in
- V
F
. In this case, the lowest possible
EXT
Figure 3 on page 7
).
(see Figure 12 on
OUT TARGET
(EQ 1)
(EQ 2)
(EQ 3)
(EQ 4)
(EQ 5)
(EQ 6)
19 - 26
).