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參數(shù)資料
| 型號： | TPS60251RTW |
| 廠商： | Texas Instruments, Inc. |
| 英文描述： | HIGH EFFICIENCY CHARGE PUMP FOR 7 WLEDs WITH I2C INTERFACE |
| 中文描述： | 高效電荷泵7，帶有I2C接口個(gè)WLED |
| 文件頁數(shù)： | 12/28頁 |
| 文件大?。?/td> | 515K |
| 代理商： | TPS60251RTW |
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LED CURRENT SINKS (DM_, DS_)
The TPS60251 has constant current sinks which drive seven individual LED current paths. Each current sink
regulates the LED current to a constant value determined by the I
2
C interface. The internal register addressing
allows the LED main channels DM1~DM5 to be controlled independently from the LED sub channels DS1~DS2.
The maximum current is programmable by the user (see the
Setting the LED Current
section). All the LED
channels sink up to 25mA of current except DM5 which has an 80-mA maximum current when configured as an
auxiliary output. Using the I
2
C interface, the user may assign DM5 to the main display bank with up to 25-mA
current or as an auxiliary output for torch or keypad light or low/weak camera flash with 80-mA current. DM5 has
64 dimming steps which is the main and sub display banks when assigned to the main display. However, it has
its own current programming register and enable control. When assigned as an auxiliary, DM5 has 4 dimming
steps (full scale, 70%, 40%, 20%).
OPEN LAMP DETECTION
In system production it is often necessary to leave LED current paths open depending on the phone model. For
example, one phone may use 2 LEDs to backlight the main display while another uses 4 LEDs. Rather than use
two different ICs for these different phone applications, the TPS60251 may be used in both applications with no
additional efficiency loss in the 2 LED applications. In traditional LED driver applications when an LED current
path is open, the current sink voltage falls to ground and the current regulation circuitry drives the output to a
maximum voltage in an attempt to regulate the current for the missing LED path. This severely reduces the
system efficiency. The TPS60251 uses 7 internal comparators to detect when an open LED condition occurs
and shut down the open current sink. The open lamp detection is enabled/disabled using the I
2
C interface.
ENABLING THE DEVICE
The TPS60251 contains a hardware enable input for situations where the IC cannot be disabled using the I
2
C
interface. Connect the EN input high to enable the device for normal operation. Connect EN low to disable the
device and place it in a low power shutdown. The hardware enable overrides the I
2
C enable. When EN is pulled
low, the TPS60251 is completely disabled (shutdown mode) and all internal registers are set to 0x00h while the
software shutdown using I
2
C keeps all internal registers.
ENABLING THE LED BANKS
The I
2
C interface is used to enable/disable the LED banks. The MAIN, SUB, and AUX LEDs are individually
controlled. Additionally, the two SUB LEDs (DS_) can be enabled independently.
CAPACITOR SELECTION
The TPS60251 is optimized to work with ceramic capacitors with a dielectric of X5R or better. The two flying
capacitors must be the same value for proper operation. The 750-kHz switching frequency requires that the
flying capacitor be less than 4.7
μ
F. Use of 1-
μ
F ceramic capacitors for both chargepump flying capacitors is
recommended.
For good input voltage filtering, low ESR ceramic capacitors are recommended. A 1-
μ
F ceramic input capacitor
is sufficient for most of the applications. For better input voltage filtering this value can be increased.
I/O INPUT
The input logic low and high threshold voltage for I
2
C interface is changed by supplying voltage to VIO. The
voltage range of VIO is 1.8V to V
I
. This allows the user to optimize the input logic low and high I
2
C threshold
voltages for the TPS60251 to cover different voltage levels for I
2
C interface for the various phone models.
TPS60251
SLVS767–APRIL 2007
APPLICATION INFORMATION (continued)
These optimized current sinks minimize the voltage headroom required to drive each LED and maximize power
efficiency by increasing the amount of time the controller stays in 1
×
mode before transitioning to 1.5
×
mode.
The output capacitor controls the amount of ripple on the output. Since small ripple is undetectable by the
human eye, a 4.7-
μ
F output capacitor works well. If better output filtering and lower ripple is desired, a larger
output capacitor may be used.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| TPS60251RTWR | 功能描述:LED照明驅(qū)動器 High Eff Charge Pump RoHS:否 制造商:STMicroelectronics 輸入電壓:11.5 V to 23 V 工作頻率: 最大電源電流:1.7 mA 輸出電流: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SO-16N |
| TPS60251RTWRG4 | 功能描述:LED照明驅(qū)動器 High Eff Charge Pump RoHS:否 制造商:STMicroelectronics 輸入電壓:11.5 V to 23 V 工作頻率: 最大電源電流:1.7 mA 輸出電流: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SO-16N |
| TPS60251RTWT | 功能描述:LED照明驅(qū)動器 High Eff Charge Pump RoHS:否 制造商:STMicroelectronics 輸入電壓:11.5 V to 23 V 工作頻率: 最大電源電流:1.7 mA 輸出電流: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SO-16N |
| TPS60251RTWT | 制造商:Texas Instruments 功能描述:DC/DC Charge Pump Converter IC |
| TPS60251RTWTG4 | 功能描述:LED照明驅(qū)動器 High Eff Charge Pump RoHS:否 制造商:STMicroelectronics 輸入電壓:11.5 V to 23 V 工作頻率: 最大電源電流:1.7 mA 輸出電流: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SO-16N |
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