MP1026
CCFL Driver
For Handheld Display Applications
The Future of Analog IC Technology
DESCRIPTION
The MP1026 is a Power IC that offers a
complete solution for driving a Cold Cathode
Fluorescent Lamp (CCFL). This Power IC
converts unregulated DC voltage to a nearly
pure sine wave required to ignite and operate
the CCFL.
The MP1026 greatly increases power
conversion efficiency and supports both analog
and burst mode dimming, simplifying the module
implementation. The MP1026 offers the
following distinct performance advantages:
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•
More light for less power
Small board implementation
Low RF emission
Low external components cost
FEATURES
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
4.5V to 14V Power Input (V
Batt
)
Increase Transformer Reliability
Open Lamp Timer and Regulation
Current and Voltage Feedback Control
Logic Level Burst Mode Control
Supports Open/Short Lamp Protection
Soft-Start
Outputs are Short Circuit Protected
Allows Burst-Mode Operation
Improved Line Transient Response
Tightened Lamp Current Accuracy
Portable DVD Players
PDAs
Camcorders
Digital Cameras
APPLICATIONS
The MP1026 is suitable for 2-Cell Li-Ion battery
applications using 5V, 9V, or 12V adapters as
the power source.
“MPS” and “Monolithic Power Systems” are Registered Trademarks of
Monolithic Power Systems, Inc.
The MP1026 is covered by US Patents 6,316,881 and 6,114,814.
TYPICAL APPLICATION
Cisb
Rs
Ccomp
CbaR
Cft
Risb
CbtR
Csfb
12
11
V
DD
20
19
18
17
16
15
D
A
14
Cs2
Rlfb
13
AGnd
Comp
PGnd
FT
ISFB
VLFB
Vdd
OutR
Batt
Rbosc
Bosc
DBrt
Abrt
IL
BtR
Rsfb
MP1026
PGnd
OutL
Batt
Vdd
BtL
En
Cp
Rdamp
Cs1
CbtL
T1
1
2
3
4
5
6
7
8
9
ABrt
R
IL
D
B
DBrt
Cbosc
CbaL
Cvdd
En
Rdbr
Cdbr
10
Rbleed
D
A
, D
B
: required for V
BATT
< 7V
IN4148 or BAT54
Gnd
Cba
V
BATT
F1
MP1026_TAC_S01
MP1026 Rev. 1.6
9/24/2007
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2007 MPS. All Rights Reserved.
1
MP1026 – CCFL DRIVER FOR HANDHELD DISPLAY APPLICATIONS
PACKAGE REFERENCE
TOP VIEW
Abrt
IL
Bosc
DBrt
En
Vdd
Batt
OutL
PGnd
BtL
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
AGnd
ISFB
VLFB
FT
Comp
Vdd
Batt
OutR
PGnd
BtR
ABSOLUTE MAXIMUM RATINGS
(1)
Input Voltage (V
BATT
).................................... 16V
Power Dissipation...................................... 1.0W
Logic Inputs .................................... 0.3V to 6.0V
IL, ISFB Inputs.................................... +6V /
–
2V
Junction Temperature...............................150°C
Lead Temperature (Solder) ......................260°C
Operating Frequency............................. 150KHz
Storage Temperature ..............
–
55°C to +150°C
Recommended Operating Conditions
(2)
Battery Voltage V
BATT
....................... 4.5V to 14V
Input Voltage V
DD
............................ 4.5V to 5.5V
Enable Voltage V
EN
............................ 0V to 5.0V
Brightness Voltage ............................ 0V to 2.0V
Operating Frequency............................... 60KHz
Operating Temperature .............
–
20°C to +85°C
EXPOSED PAD
CONNECT TO
AGND (PIN 20)
Thermal Resistance
MP1026_PD01-TSSOP20F
(3)
TSSOP20F ............................. 40 ....... 6....
°C/W
Notes:
1) Exceeding these ratings may damage the device.
2) The device is not guaranteed to function outside of its
operating conditions.
3) Measured on approximately 1” square of 1 oz copper.
θ
JA
θ
JC
Part Number*
MP1026EF
*
Package
TSSOP20F
Temperature
–20°C to +85°C
For Tape & Reel, add suffix –Z (eg. MP1026EF–Z)
For Lead Free, add suffix –LF (eg. MP1026EF–LF–Z)
ELECTRICAL CHARACTERISTICS
Batt = 14V, V
DD
= 5V, T
A
= +25°C, unless otherwise noted.
Parameter
Voltage Supply
Vdd Off Current
Batt Off Current
Vdd Current (operating)
Shutdown Logic
Fault Timer Threshold
Fault Timer Sink Current
Fault Timer Source Current
Open Lamp
Secondary Overload
Enable Voltage Low
Enable Voltage High
Symbol Condition
Idd(off) Enable = 0V
IBatt(off) enable = 0V
Idd(on)
Vth(FT)
V(VLFB) > 0, V(ISFB) < 1.2
V(VLFB) > 0, V(ISFB) < 1.2
V(ISFB) > 1.2
VL(En)
VH(En)
1.5
Min
Typ
Max
400
20
1.8
Units
µA
µA
mA
V
µA
µA
µA
V
V
1.2
1.2
1
1
115
0.6
MP1026 Rev. 1.6
9/24/2007
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2007 MPS. All Rights Reserved.
2
MP1026 – CCFL DRIVER FOR HANDHELD DISPLAY APPLICATIONS
ELECTRICAL CHARACTERISTICS
(continued)
Batt = 14V, V
DD
= 5V, T
A
= +25°C, unless otherwise noted.
Parameter
Output Drivers
Switch On Resistance
(4)
Symbol
R
(ON)OUTL,O
UTR
Condition
Min
0.085
Typ
0.12
1800
350
8300
1300
Max
0.15
Units
Ω
ns
ns
ns
ns
Ton(min) Vdd = 5V
Batt = 4.5V, Vcomp = 0V
Ton(min) Vdd = 5V
Batt = 14V, Vcomp = 0V
First Pulse Ton(min)
Batt = 4.5V
Vdd = 5V
First Pulse Ton(min)
Batt = 14V
Vdd = 5V
Brightness Control
Sense Full Brightness
V(IL)
V(Abrt) = 2.0V
Sense Full Dim
V(IL)
V(Abrt) = 0V
Lamp Current Regulation
4.5v < V(Batt) < 14V
Burst Oscillator Sink Current
I(Bos)
Burst Oscillator Peak
V(Bos)
Voltage
Fault Loop Control
Open Lamp Threshold
Vth(VLFB)
Secondary Current
Vth(ISFB)
Threshold
Fault Mode Comp Current
I(Cmp) V(VLFB) < 0V, V(ISFB) > 1.2V
Note:
4) This parameter is guaranteed by design.
360
100
385
115
3
370
1.8
0
1.2
460
410
130
mV
mV
%
µA
V
V
V
µA
PIN FUNCTIONS
Pin #
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Name
ABrt
IL
Bosc
DBrt
En
Vdd
Batt
OutL
PGnd
BtL
BtR
PGnd
OutR
Batt
Vdd
Comp
FT
VLFB
ISFB
AGnd
Description
Analog Dimming.
Lamp Current Feedback Sense Input.
Burst Oscillator Timing.
Burst Mode Dimming.
Chip Enable. Do not float this pin.
Supply Voltage.
Power Supply Input.
Output to Load (Tank Circuit).
Power Ground.
Regulated Output Voltage for Bootstrap Cap on Phase L.
Regulated Output Voltage for Bootstrap Cap on Phase R.
Power Ground.
Output to Load (Tank Circuit).
Power Supply Input.
Supply Voltage.
Loop Compensation Cap.
Fault Timer.
Open Lamp Detect (Lamp Voltage Feedback).
Shorted Lamp Detect (Secondary Current Feedback).
Small Signal Ground (Connect the Exposed Pad to Pin 20).
MP1026 Rev. 1.6
9/24/2007
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2007 MPS. All Rights Reserved.
3
MP1026 – CCFL DRIVER FOR HANDHELD DISPLAY APPLICATIONS
BLOCK DIAGRAM
Vdd
DBrt
Bosc
6, 15
4
3
BURST
DIMMING
RAMP
OSCILLATOR
+
V
DRV
--
BURST
DIMMING
CLOCK
+
--
8
+
--
CONTROL
LOGIC
9, 12 PGnd
--
+
13 OutR
--
+
14 Batt
11 BtR
SHORT
CIRCUIT
FT 17
PROTECTION
+
--
19 ISFB
1.2V
OutL
20 AGnd
REF
10 BtL
7
Batt
ENABLE
5
En
OPEN LAMP
FAULT
(OLF)
+
--
COMP
--
GM
+
HALF
WAVE
RECTIFIER
18 VLFB
2
IL
Comp 16
1
Abrt
MP1026_BD01
Figure 1—Functional Block Diagram
MP1026 Rev. 1.6
9/24/2007
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2007 MPS. All Rights Reserved.
4
MP1026 – CCFL DRIVER FOR HANDHELD DISPLAY APPLICATIONS
APPLICATION INFORMATION
Brightness Control
The MP1026 can operate in three modes:
Analog Mode, Burst Mode with a DC input, or
Burst Mode with an external PWM. The three
modes are dependent on the pin connections
as per Table 1.
Choosing the required burst repetition
frequency can be achieved by an RC
combination, as defined below. The MP1026
has a soft on and soft off feature to reduce
noise, when using burst mode dimming.
1. Select a Minimum Duty Cycle (D
MIN
). This is
the ratio T
FALL
/ (T
FALL
+ T
RISE
) for the burst
oscillator.
For example: 10%
2. Determine Rbosc by the formula:
⎤
⎡⎡
1
⎤
−
1)
⎥
⎥
⎢ ⎢
1.68
×
(
D
MIN
⎢⎢
⎥ +
4
⎥
⎥
⎢⎢
0.42
⎥
⎥
⎢⎢
⎥
⎦
⎦
⎣⎣
Rbosc
=
−
6
350
×
10
Brightness Polarity:
Burst: 100% duty cycle is at 1.8V
Analog: 1.9V is maximum brightness
Fault Protection
Open Lamp: The VLFB pin (#18) is used to
detect whether an open lamp condition has
occurred. During normal operation the VLFB pin
is typically at 5V DC with an AC swing of ±2.5V.
If an open lamp condition exists then the AC
voltage on the VLFB line will swing below zero
volts. When that occurs, the IC regulates the
VLFB voltage to 10V p-p and a 1µA current
source will inject into the FT pin. If the voltage
at the FT pin exceeds 1.2V, then the chip will
shut down.
Excessive Secondary Current (Shorted Lamp
and UL safety specs): The ISFB pin (#19) is
used to detect whether excessive secondary
current has occurred. During normal operation
the peak ISFB voltage is below 1.2V. If a fault
condition occurs that increases the secondary
current, then the voltage at ISFB will be greater
than 1.2V. When that occurs, a 120µA current
source will inject into the FT pin. If the voltage
at the FT pin exceeds 1.2V, then the chip will
shut down.
The following is the design reference for the
secondary winding current.
Sensing network: Rsfb, Risb, Csfb and Cisb.
Rsfb
>
1 .2 V
=
1.7k
Ω
0.7mA
3. Select a burst frequency and find T
TOTAL
where:
T
TOTAL
= 1/burst frequency.
Then determine Cbosc by the formula:
Cbosc
=
(1
−
D
MIN
)
0.42
×
Rbosc
×
f
bosc
Where f
bosc
is burst frequency rate in Hz and
T
min
is the Minimum burst time in sec.
In a typical application, Rbosc=470kΩ and
Cbosc=22nF.
Table 1—Function Mode
Function
Analog Mode
Burst Mode with
DC input voltage
Burst Mode from
external source
Pin Connection
Pin 1
Pin 4
Pin 3
ABrt
DBrt
Bosc
0 – 1.9V
V
Ref
AGnd
Rbosc
V
Ref
0 – 1.8V
Cbosc
V
Ref
PWM
1.5V
The recommended value is 3.9kΩ to 10kΩ
(typically 4.7kΩ).
Csfb
<
0.7 mA
KHz
=
93nF
1 . 2 V
×
2
π
Select a capacitor with less than 93nF
capacitance for Csfb and make the FB pin
voltage peak value around 0.9V in normal
operation.
The 0.7mA DC and 0.7mA/KHz AC current
values are taken from the UL60950 safety
requirement.
MP1026 Rev. 1.6
9/24/2007
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2007 MPS. All Rights Reserved.
5
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