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参数资料
| 型号： | DS3988T+T&R |
| 厂商： | Maxim Integrated |
| 文件页数： | 14/23页 |
| 文件大小： | 0K |
| 描述： | IC CCFL CNTRLR 8CH 48TQFP |
| 标准包装： | 2,000 |
| 类型： | CCFL 控制器 |
| 频率： | 40 ~ 80 kHz |
| 电流 - 电源： | 15mA |
| 电源电压： | 4.5 V ~ 5.5 V |
| 工作温度： | -40°C ~ 85°C |
| 封装/外壳： | 48-LQFP |
| 供应商设备封装： | 48-LQFP（7x7） |
| 包装： | 带卷 (TR) |
8-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
SVM
DS3988
where K = 1600k ? ? kHz for lamp frequency calcula-
tions. When calculating the resistor value for the dim-
ming clock frequency, K will be one of four values as
determined by the desired frequency and the POSCR0
R 1
2.0V
V TRIP = 2 . 0 ? 1 2 ?
and POSCR1 bit settings as shown in the Control
Register 2 (CR2) table 4 in the Detailed Register
Descriptions section.
Example: Selecting the resistor values to configure a
DS3988 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 ?? kHz. For the lamp frequency resistor (R LOSC ) cal-
culation, K = 1600k ?? 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:
EXAMPLE: R 1 = 10k ? , R 2 = 40k ? SETS AN SVM TRIP POINT OF 10V
Figure 7. 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
lockout (UVLO) that prevents operation when the DS3988
R LOSC =
1600 k ? ? kHz
50 kHz
= 32 k ? ,
does not have adequate voltage for its analog circuitry to
operate or to drive the external MOSFETs. The V CC moni-
tor features hysteresis to prevent V CC noise from causing
R POSC =
4 k ? ? kHz
0 . 160 kHz
= 25 . 0 k ?
spurious operation when V CC is near the trip point. This
monitor cannot be disabled by any means.
Fault Monitoring
Supply Monitoring
The DS3988 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 7) 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
The DS3988 provides extensive fault monitoring for
each channel. It can detect open-lamp, lamp overcur-
rent, failure to strike, and overvoltage conditions. The
DS3988 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 DS3988 is power-cycled or the
inverter’s DC supply is power-cycled. The DS3988 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 CR1 and CR2.
14
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相关代理商/技术参数 |
参数描述 |
|---|---|
| DS3991 | 制造商:MAXIM 制造商全称:Maxim Integrated Products 功能描述:Low-Cost CCFL Controller |
| DS3991V | 制造商:MAXIM 制造商全称:Maxim Integrated Products 功能描述:Low-Cost CCFL Controller |
| DS3991VC | 制造商:MAXIM 制造商全称:Maxim Integrated Products 功能描述:Low-Cost CCFL Controller |
| DS3991VR | 制造商:MAXIM 制造商全称:Maxim Integrated Products 功能描述:Low-Cost CCFL Controller |
| DS3991VRC | 制造商:MAXIM 制造商全称:Maxim Integrated Products 功能描述:Low-Cost CCFL Controller |
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