参数资料
| 型号： | DS3994Z+T&R |
| 厂商： | Maxim Integrated |
| 文件页数： | 16/28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
Setting the Lamp and Dimming Clock (DPWM)
Frequencies Using External Resistors
Both the lamp and dimming clock frequencies can be
set using external resistors. The resistance required for
either frequency can be determined using the following
V INV
formula:
R OSC =
K
f OSC
R 2
R 1
SVM
DS3994
V TRIP = 2 . 0 ? 1 2 ?
where K = 1600kΩ?kHz for lamp frequency calculations.
When calculating the resistor value for the dimming clock
frequency, K will be one of four values as determined by
the desired frequency and the POSCR0 and POSCR1 bit
settings as shown in the Control Register 2 (CR2) in the
Detailed Register Descriptions section.
Example: Selecting the resistor values to configure a
DS3994 to have a 50kHz lamp frequency and a 160Hz
dimming clock frequency:
For this configuration, POSCR0 and POSCR1 must be
programmed to 1 and 0, respectively, to select 90Hz to
220Hz as the dimming clock frequency range. This sets
K for the dimming clock resistor (R POSC ) calculation to
4k Ω ? kHz. For the lamp frequency resistor (R LOSC ) cal-
culation, K = 1600k Ω ? kHz, which allows the lamp fre-
quency K value regardless of the frequency. The
formula above can now be used to calculate the resis-
tor values for R LOSC and R POSC as follows:
2.0V
EXAMPLE: R 1 = 10k Ω , R 2 = 40k Ω SETS AN SVM TRIP POINT OF 10V.
Figure 8. Setting the SVM Threshold Voltage
problems. Proper use of the SVM can prevent these
problems. If desired, the SVM can be disabled by con-
necting the SVM pin to V CC .
? R + R ?
? R 1 ?
The V CC monitor is used as a 5V supply undervoltage
R LOSC =
1600 k Ω ? kHz
50 kHz
= 32 k Ω ,
lockout (UVLO) that prevents operation when the DS3994
does not have adequate voltage for its analog circuitry to
operate or to drive the external MOSFETs. The V CC moni-
R POSC =
4 k Ω ? kHz
0 . 160 kHz
= 25 . 0 k Ω
tor features hysteresis to prevent V CC noise from causing
spurious operation when V CC is near the trip point. This
monitor cannot be disabled by any means.
Supply Monitoring
The DS3994 monitors both the transformer’s DC supply
and its own V CC supply to ensure that both voltage lev-
els are adequate for proper operation.
The inverter’s transformer supply (V INV ) is monitored
using an external resistor-divider that is the input into a
comparator (see Figure 8) with a 2V threshold. Using
the equation below to determine the resistor values, the
supply voltage monitor (SVM) trip point (V TRIP ) can be
customized to shut off the inverter when the trans-
former’s input voltage drops below any specified value.
Operating with the transformer’s supply at too low of a
level can prevent the inverter from reaching the strike
voltage and could potentially cause numerous other
Fault Monitoring
The DS3994 provides extensive fault monitoring for
each channel. It can detect open-lamp, lamp overcur-
rent, failure to strike, and overvoltage conditions. The
DS3994 can be configured to disable all channels if
one or more channels enter a Fault State, or it can be
configured to disable only the channel where the fault
occurred. Once a Fault State has been entered, the
FAULT output is asserted and the channel(s) remain
disabled until either the DS3994 is power-cycled or the
inverter’s DC supply is power-cycled. The DS3994 can
also be configured to automatically attempt to clear a
detected fault (except lamp overcurrent) by restriking the
lamp, as explained in Step 4. Configuration bits for the
fault monitoring options are located in the control registers.
16
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