参数资料
| 型号： | DS3994Z+T&R |
| 厂商： | Maxim Integrated |
| 文件页数： | 25/28页 |
| 文件大小： | 0K |
| 描述： | IC CCFL CNTRLR 4CH 28-SOIC |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 1,000 |
| 类型： | CCFL 控制器 |
| 频率： | 20 ~ 80 kHz |
| 电流 - 电源： | 9mA |
| 电源电压： | 4.5 V ~ 5.5 V |
| 工作温度： | -40°C ~ 85°C |
| 封装/外壳： | 28-SOIC（0.295"，7.50mm 宽） |
| 供应商设备封装： | 28-SOIC W |
| 包装： | 带卷 (TR) |
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4-Channel Cold-Cathode
Fluorescent Lamp Controller
COMMUNICATIONS KEY
NOTES
S
P
START
STOP
A
N
ACK
NOT
ACK
WHITE BOXES INDICATE THE MASTER IS
CONTROLLING SDA
SHADED BOXES INDICATE THE SLAVE IS
CONTROLLING SDA
1) ALL BYTES ARE SENT MOST SIGNIFICANT BIT FIRST.
2) THE FIRST BYTE SENT AFTER A START CONDITION IS
ALWAYS THE SLAVE ADDRESS FOLLOWED BY THE
SR
REPEATED
START
X
X
X
X
X
X
X
X
8-BITS ADDRESS OR DATA
READ/WRITE BIT.
WRITE A SINGLE BYTE
S
1 0
1
0 0
0 A 0 0
A
MEMORY ADDRESS
A
DATA
A
P
READ A SINGLE BYTE
S
1 0
1
0 0
0 A 0 0
A
MEMORY ADDRESS
A
SR
1 0
1
0 0
0 A 0 1
A
DATA
N
P
Figure 12. I 2 C Communications Examples
Applications Information
Addressing Multiple DS3994s On a
Common I 2 C Bus
Each DS3994 responds to one of two possible slave
addresses based on the state of the address input (A 0 ).
For information about device addressing see the I 2 C
Communications section.
Power-Supply Decoupling
To achieve best results, it is recommended that each
V CC pin is decoupled with a 0.01μF or a 0.1μF capacitor
to GND. Use high-quality, ceramic, surface-mount capac-
itors, and mount the capacitors as close as possible to
the V CC and GND pins to minimize trace inductance.
Setting the RMS Lamp Current
Resistor R8 in the typical operating circuit (Figure 13)
sets the lamp current. R8 = 140 Ω corresponds to a
5mA RMS lamp current as long as the current waveform
is approximately sinusoidal. The formula to determine
the resistor value for a given sinusoidal lamp current is:
Component Selection
External component selection has a large impact on the
overall system performance and cost. The two most
important external components are the transformers
and n-channel MOSFETs.
The transformer should be able to operate in the 20kHz
to 80kHz frequency range of the DS3994, and the turns
ratio should be selected so the MOSFET drivers run at
28% to 35% duty cycle during steady state operation.
The transformer must be able to withstand the high
open-circuit voltage that will be used to strike the lamp.
Additionally, its primary/secondary resistance and
inductance characteristics must be considered
because they contribute significantly to determining the
efficiency and transient response of the system. Table 5
shows a transformer specification that has been utilized
for a 12V inverter supply, 438mm x 2.2mm lamp design.
The n-channel MOSFET must have a threshold voltage
that is low enough to work with logic-level signals, a low
on-resistance to maximize efficiency and limit the n-
channel MOSFET’s power dissipation, and a break-
down voltage high enough to handle the transient. The
R 8 =
1
2 × I LAMP ( RMS )
breakdown voltage should be a minimum of 3x the
inverter voltage supply. Additionally, the total gate
charge must be less than Q G , which is specified in the
Recommended Operating Conditions table. These
specifications are easily met by many of the dual n-
channel MOSFETs now available in SO-8 packages.
Table 6 lists suggested values for the external resistors
and capacitors used in the typical operating circuit.
____________________________________________________________________
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