MIC2841AYMT TR Micrel Inc, MIC2841AYMT TR Datasheet - Page 8

• Manufacturer Part Number: MIC2841AYMT TR
• Description: IC LED DRIVR WHITE BCKLGT 10TMLF
• Manufacturer: Micrel Inc
• Type: Backlight, White LEDr

Specifications of MIC2841AYMT TR

• Constant Current: Yes
• Topology: Linear (LDO), PWM
• Number Of Outputs: 4
• Internal Driver: Yes
• Type - Primary: Backlight, Flash/Torch
• Type - Secondary: White LED
• Frequency: 500kHz
• Voltage - Supply: 3 V ~ 5.5 V
• Mounting Type: Surface Mount
• Package / Case: 10-TMLF®
• Operating Temperature: -40°C ~ 125°C
• Current - Output / Channel: 20mA
• Internal Switch(s): Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Output: -
• Efficiency: -
• Other names: 576-3471-2

Application Information
Dynamic Average Matching (DAM™)
The
multiplexes four voltage references to provide highly
accurate LED current and channel matching. The
MIC2841A achieves industry leading LED channel
matching of 1.5% across the entire dimming range.
Ultra Fast PWM™ Dimming Interface
The MIC2841A supports a wide range of PWM control
signal frequencies from 200Hz to 500kHz. This
extremely wide range of control provides ultimate
flexibility for handheld applications using high frequency
PWM control signals.
WLED dimming is achieved by pulse width modulating
the linear drivers which are controlled by a PWM signal
to the END pin. For PWM frequencies between 200Hz –
20kHz the MIC2841A supports a duty cycle range from
1% to 100%, see Figure3. The MIC2841A incorporates
an internal shutdown delay to ensure that the internal
control circuitry remains active during PWM dimming.
This feature prevents the possibility of backlight
flickering when using low frequency PWM control
signals. The MIC2841A also supports Ultra Fast PWM™
frequencies from 20kHz to 500kHz. Due to input signal
propagation delay, PWM frequencies above 20kHz have
a non-linear relationship between the duty cycle and the
average LED current, see Figures 4 and 5. Figures 6
through 10 show the WLED current response when a
PWM signal is applied to the END pin
(1)
15kHz may require a logic high enable signal for 80μs to
first enable the MIC2841A prior to PWM dimming.
Micrel Inc.
June 2009
From the low Iq sleep mode PWM frequencies above
by Changing PWM Duty Cycle for PWM Frequencies
Figure 3. Average Current per LED Dimming
Dynamic
Average
up to 20kHz
Matching™
(1)
.
architecture
8
Figure 4. Channel Current Response to PWM Control
Signal Frequencies from 50kHz to 500kHz
Figure 5. Minimum Duty Cycle
for Varying PWM Frequency
M9999-062909-C
MIC2841A