RT9300AGE Richtek USA Inc, RT9300AGE Datasheet - Page 7

• Manufacturer Part Number: RT9300AGE
• Description: IC LED DVR WHITE BCKLGT SOT23-6
• Manufacturer: Richtek USA Inc

Specifications of RT9300AGE

• Constant Current: Yes
• Internal Driver: Yes
• Type - Primary: Backlight, General Purpose
• Type - Secondary: White LED
• Mounting Type: Surface Mount
• Topology: Linear (LDO), PWM
• Number Of Outputs: 4
• Voltage - Supply: 2.5 V ~ 5.5 V
• Package / Case: SOT-23-6
• Operating Temperature: -40°C ~ 85°C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Frequency: -
• Voltage - Output: -

Applications Information
The RT9300A/B is a 4-Channel current source driver for
white LEDs.
Enable Input
EN powers the input of the RT9300A/B. This IC provides
an under voltage lockout (UVLO) function to prevent it from
unstable issue when startup. The UVLO threshold of input
falling voltage is set at 2.1V typically with a hysteresis
0.1V.Drive EN high to enable the device; drive EN low to
disable the device. When driven high, EN draws 350uA to
power the IC. Driving EN low forces LED1, LED2, LED3,
and LED4 into a high-impedance state.
LED Current
RT9300A/B provides a constant current for white LED.
Figure 1 shows a typical application circuit for 4 white
LEDs. Each channel supports up to 20mA/15mA current
and regulates a constant current for uniform intensity. For
keypad LED application, the all channels must be
connected to LED as shown in Figure 2. In order to maintain
LED constant current, the input voltage must provide the
required LED forward voltage and current source dropout
voltage. If the forward voltage of white LEDs is 3.3V, the
input voltage should be higher than 3.4V to provide enough
voltage headroom for maintaining constant brightness.
LED Brightness Dimming Control
For controlling the LED brightness, the RT9300A/B can
perform the dimming control by applying a PWM signal to
EN pin. When an external PWM signal is connected to
the EN pin, brightness of white LED is adjusted by the
duty cycle. The average LED current is proportional to the
PWM signal duty cycle. The magnitude of the PWM signal
must be higher than the minimum level of enable input
high level, in order to let the dimming control perform
correctly, the suggested PWM frequency range is 10kHz
to 200Hz.
Thermal Considerations
For continuous operation, do not exceed absolute
maximum operation junction temperature 125°C. The
maximum power dissipation depends on the thermal
resistance of IC package, PCB layout, the rate of
DS9300A/B-04 October 2008
surroundings airflow and temperature difference between
junction to ambient. The maximum power dissipation can
be calculated by following formula :
P
Where T
temperature 125°C, T
the θ
For recommended operating conditions specification of
RT9300, where T
temperature of the die (125°C) and T
ambient temperature. The junction to ambient thermal
resistance θ
packages, the thermal resistance θ
standard JEDEC 51-3 single-layer thermal test board. The
maximum power dissipation at T
by following formula :
P
SOT-23-6 packages
The maximum power dissipation depends on operating
ambient temperature for fixed T
θ
allows the designer to see the effect of rising ambient
temperature on the maximum power allowed.
JA
D(MAX)
D(MAX)
. For RT9300 packages, the Figure 1 of derating curves
Figure 1. Derating Curves for RT9300 Packages
500
450
400
350
300
250
200
150
100
JA
50
0
is the junction to ambient thermal resistance.
= ( T
= (125°C − 25°C) / (250°C/W) = 0.4W for
0
J(MAX)
J(MAX)
JA
is the maximum operation junction
is layout dependent. For SOT-23-6
25
- T
Ambient Temperature (°C)
J(MAX)
A
) / θ
A
is the ambient temperature and
50
JA
is the maximum junction
SOT-23-6
J(MAX)
A
RT9300A/B
= 25°C can be calculated
and thermal resistance
75
JA
is 250°C/W on the
A
Single Layer PCB
is the maximum
www.richtek.com
100
125
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