mp1010bef MPS, mp1010bef Datasheet - Page 6

• Manufacturer Part Number: mp1010bef
• Description: Cold Cathode Fluorescent Lamp Driver
• Manufacturer: MPS

APPLICATION INFORMATION
Brightness Control
The maximum lamp current is set by Rlfb:
Where V
lamp current, Rlfb = 139Ω. Use a 140Ω ±1%
resistor for the application.
The MP1010B can adjust the lamp brightness
in three operating modes: Analog Mode, Burst
Mode with a DC input, or Burst Mode with
external PWM. The Burst Mode with a DC input
is not recommended if the dimming steps
required
applications, please select the MP1016 or
MP1028.
The three modes are dependent on the pin
connections as per the table below.
The PWM signal should be 200Hz (±50Hz) for
the best possible performance. For different
panels, the burst frequency may need adjusting
to avoid possible interference with the LCD
horizontal scan frequency. The PWM signal
High level should be larger than 1.7V but less
than 5V. The Low level should be smaller than
0.7V but higher than 0V. It is recommended that
the PWM minimum pulse be longer than 250µs,
and that the pulse rising and falling edges be
less than 0.5µs. The PWM signal should be
connected to the DBRT pin directly (Rdbr = 0Ω
and remove Cdbr).
MP1010B Rev. 2.2
9/24/2007
Options
Burst Mode
with PWM
Input
Analog Mode
with DC Input
Burst Mode
with DC Input
Table 1—Dimming Mode Selection
IL_MAX
are
= 379mV, typically. For a 6mA
Rlfb
(ABRT)
Pin 1
0V to
1.9V
more
V
V
REF
REF
=
2
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
2 .
I
LAMP
(DBRT)
×
than
PWM
Pin 4
0V to
1.8V
V
V
REF
IL
_
RMS
_
MAX
10.
Rbosc Cbosc
220kΩ
220kΩ
220kΩ
Pin 3 (BOSC)
For
MP1010B – COLD CATHODE FLUORESCENT LAMP DRIVER
© 2007 MPS. All Rights Reserved.
100kΩ/
100kΩ
47nF
47nF
www.MonolithicPower.com
such
RMS
For an application with either Analog Mode or
no dimming, the BOSC pin can be shorted to
Analog GND to simplify the circuit.
For analog dimming, a voltage between 1.9V
and 5V sets the maximum brightness. 0V sets
the minimal brightness, wherein lamp current is
1/3 of the maximum value. Most applications
need a RC filter to eradicate noises before the
DC signal reaches the ABRT
suggested values are Rabr=47kΩ, Cabr=0.1µF.
For burst dimming with a DC input, a voltage
between 1.8V and 5V sets the maximum duty
cycle (100%). 0V sets the minimum duty cycle,
which is related to the design of Rbosc and
Cbosc. Again, most applications need a RC
filter to eradicate noises before the DC signal
reaches the DBRT pin. The suggested values
are Rdbr=47kΩ, Cdbr=0.1µF.
Select Rbosc and Cbosc based on the
following:
1. Select a burst frequency f
2. Design the minimal duty cycle to meet the
minimal pulse request for the lamp.
3. Determine Rbosc by the formula:
4. Determine Cbosc by the formula:
For a typical design, Rbosc=220kΩ and
C1=47nF.
Rbosc
Cbosc
D
≅
MIN
≈
. 0
. 0
42
≥
42
250
×
D
×
1 (
Rbosc
µ
MIN
−
s
. 1
×
D
68
×
BOSC
f
MIN
BOSC
350
×
)
f
for the panel.
BOSC
×
10
−
6
pin. The
6