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PDF ( 数据手册 , 数据表 ) OZ9938

零件编号 OZ9938
描述 LCDM Inverter Controller
制造商 O2 Micro
LOGO O2 Micro LOGO 


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OZ9938 数据手册, 描述, 功能
CHANGES
No. Applicable Section
1. Electrical Characteristics
2. Throughout datasheet
OZ9938
Change Summary
Description
Update rotection release threshold in ‘Timer & protection’
parameter Min & Max limits
Miscellaneous changes
Page(s)
3
---
REVISION HISTORY
Revision No.
0.60
0.65
1.0
Description of change
Initial release
1. Electrical Characteristics: a. Modify general test conditions in line 1; b.
Modify ‘Driver Frequency – Striking & Normal Operation’ Typ limit; c.
Modify ‘PWM Dimming Control – LCT frequency’. 2. Reference Application
Circuit: Modify C14, C9 & R9 values
1. Ordering Information: Add OZ9938G, IG, D & DN. 2. Recommended
Operating Range: a. Add ‘Dimming Range’; b. Fill in ‘Thermal Impedance’.
3. Electrical Characteristics: a. Update ‘Supply Current’ limits; b. Update
‘Soft Start’ limits; c. Update ‘Under Voltage Lockout’ limits; d. Update
‘Reference Voltage’ limits; e. Update ‘Driver Frequency’ limits; f. Update
‘Timer & Protection’ limits; g. Update ‘Drivers’ parameter name & limits; h.
Update ‘PWM Dimming Control’ limits; i. Delete ‘Analog Dimming Control’.
4. Function Description: Update formula in NO. 4 Ignition, No. 6 Normal
Operation & No. 9 Dimming Control. 5. Package Information: Add DIP
package drawing.
Release Date
5/12/2005
6/27/2005
9/22/2005
10/14/2005
OZ9938-DS-1.1
Copyright 2005 by O2Micro
All Rights Reserved
Patent#6,559,606, #6,856,519 & #6,809,938
www.DataSheet4U.net
Page 0
CONFIDENTIAL







OZ9938 pdf, 数据表
To resume operation, toggle the ENA signal or
restart VDDA.
8. Over-Voltage and Over-Current
Protection
Over-voltage and over-current protection are
monitored by the voltage on VSEN (pin 6).
During normal operation, if a CCFL is damaged
or removed, the voltage at VSEN (pin 6)
increases. Once the voltage at VSEN exceeds
the user-defined, preset voltage set by OVPT (pin
7), the driver output duty cycle is regulated and
the shutdown delay timer is activated. OVPT
sets the overall protection threshold voltage that
is lower than ~3V (VSEN threshold). Once the
voltage at TIMR pin reaches ~3V, the IC will shut
down and latch. OVPT voltage setting is
determined by a resistor divider (R13 and R16)
connected to the OVPT.
The approximate shutdown delay time is
calculated by the following equation.
Td [Sec] = 0.33 XCTIMER [uF]
To resume operation, toggle the PWM signal or
restart VDDA.
9. Dimming Control
A built-in function enables the user to select one
of the following dimming controls: analog, internal
LPWM or external PWM signal.
Analog dimming control is activated when the
voltage to LCT (pin 11) is greater than 3V. A
voltage of 0.5V to 1.25V applied to DIM (pin 4)
controls the amplitude of the lamp current.
Internal LPWM dimming control is determined by
resistor R8 and capacitor C14 connected to LCT.
The low frequency sawtooth waveform is
compared with the voltage at DIM to generate the
LPWM signal. The peak and valley of the
waveform are 1.5V and 0.1V respectively. The
frequency is approximated by the following
equation:
f LOSC =
3102
RLCT [M ]*CLCT[nF]
[Hz]
With positive PWM dimming polarity, the LPWM
duty cycle will be 100% when DIM pin voltage is
higher than 1.5V. LCD panel will have maximum
brightness. When DIM pin voltage is lower than
0.1V, the LPWM duty cycle will be 0%. LCD
panel will be totally dark.
OZ9938
External PWM dimming is implemented by
setting LCT to a DC voltage between 0.5V to
1.0V using a resistor divider (R8 and R17)
between VDDA and GND. Apply the external
PWM pulse to DIM (pin 4).
.
CONFIDENTIAL
OZ9938-DS-1.1
Page 7














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