Features and advantages

#9642; proprietary adaptive control scheme (1 ×, 1.5 ×, 2 ×)

#9642; 0.5%typical WLED current match [123 123 ]

#9642; up to 6 white LED

#9642; main display screen backlight (up to 6 wleds)

#9642; main display and secondary display backlight

#9642; main display and low -current flash/flashlight

#9642; every wled 30 mAh

#9642; 2 × serial lighting interface

#9642; 320 mAh charge pump capacity

#9642; low electromagnetic interference design and soft startup function

#9642; short circuit, over pressure, heat, heat Shipping protection

#9642; 0.75 mm nominal height (very thin shape), 3 × 3 mm packaging 6 -channel high -efficiency charge pump white LED drive

Packaging: 16 -pin QFN/mlp (Suffix ES)

Instructions

A8434

High -efficiency charge pump integrated circuit provides a simple, low -cost WLED (white LED ) Drive solution, used to drive up to six WLEDs in various applications, can be a single display of all six backlights, or multiple displays, such as four WLEDs as the main display backlit, while the other two wled wled Used for backlight or small current flash/flashlight for the sub -display. A8434 uses a proprietary control scheme (1 ×, 1.5 ×, 2 ×). While maintaining the highest efficiency and low electromagnetic interference, it can also output a good WLED current. WLED current adjusts the entire lithium battery voltage range to provide uniform strength. The main display and auxiliary display/welding gun can control the brightness and opening/level through 2 single -line serial interface pins.

A8434 uses QFN/MLP-16 to save space (3 × 3 mm covers an area) ES packaging.

The application includes:

#9642; white LED backlight for mobile phones, PDA

#9642; digital camera, camera

#9642; Portable audio equipment and mp3

#9642; other portable devices white LED backlight

Typical application

Function box diagram

Packaging thermal characteristics

Rθja 47 ° C/W, on the 4 -layer board based on Jedec, additional information can be obtained on the Allegra website.

Equipment packaging is not lead, 100%matte tin -plated leading framework.

Performance characteristics

Test TA 25 ° C using the application circuit shown in FIG. 2, vehicle identification number 3.6 V (unless there is another instructions).

Application information Set LED current

Use the following Formula, use RSET settings to display the full backlight (100%) on LED1 to LED6. The maximum current of a LED should not exceed 30 mAh:

, the RSET is ω, and ILEDX is ampere.

Transition between 1 × and 1.5 × or 2 × modulus

A8434 adaptive selection working mode. When VIN is high enough to keep VLEDX GT; 150 MV, A8434 works in 1 × mode, unless the LEDX node drops below the 150 MV threshold unless VIN decreases. When VLEDX is less than 150mv, IC enters 1.5 × mode.

When A8434 was switched from 1 × mode to 2 × mode, it first switched to 1.5 × mode, the typical duration was 1 ms, and then entered the 2 × mode.

When working in 1.5 × mode, if Vout LT; vin, IC switch back to 1 × mode every 130ms, and then enter the 1.5 × mode again when necessary.

Transition between 1.5 × and 2 × modulus

The conversion from 1.5 × mode to 2 × mode depends on dropouts.

When working in 2 × mode, IC switch back to 1.5 × mode every 130ms, and re -enter the 2 × mode if necessary. In addition, when the 2 × mode is in the 2 × mode, the channel disable is detected (that is, when ENM keeps the low level exceeds 0.5ms, ENF remains high level, vice versa), IC automatically recovers to 1.5 × mode, and then necessary Time to enter the 2 × mode again.

Light

Main display LED1 to LED4 darkens. The brightness of the main display wleds (LED1 to LED4) and the opening/off/off can be controlled by the digital input of ENM pins. The ENM pin receives the first -line serial pulse input to enable A8434 and sets 11 light levels, from 100%to 5%.

When ENM initially started from the shutdown state, it wasAfter moving, the current of the WLEDS is programmed as 100%set current, which is determined by the current of the ISET pin. Subsequent pulse reduces the current of the backlight LED by 10%, while the 10th pulse reduces the current by 5%. The next pulse recovers 100%(all) brightness. Figure 5 shows the timing diagram of ENM control.

Sub -display LED5 and LED6 operations. The brightness of the sub -display backlit LED (LED5 and LED6) and the opening/off can be controlled by the digital input of the ENS pin. ENS pin accepts the first -line serial pulse input to enable A8434 and set 11 light -adjusting levels from 100%to 5%.

When ENS initially started from the shutdown state, after the soft start, the current of the backlight LED was programmed to set 100%of the current, which was determined by the current of the ISET pin. Subsequent pulse reduces the LED current by 10%, and the 10th pulse reduces the current by 5%. The next pulse recovers 100%(all) brightness. Figure 5 shows the timing chart of the ENS control.

All 6 LEDs changed at the same time

For larger display, 6 LEDs can be combined together. By linked ENM and ENS together and applied serial pulses for lighting, LED LED1 to LED6 can be dimmed at the same time, as shown in Figure 1.

Absolute horizontal operations need to be dimmed to a specific level, regardless of the current dimension level.

For example, if the IC is darken to 30%, this can be completed through 7 steps, as shown in Figure 5 without considering the actual level of light adjustment. This can be achieved by pulling the corresponding ENX pins below the TSHDN, and then applied to the pulse shown in Figure 5 (30%light adjustment to 7). If the pulse is applied within 2-3 milliseconds, the flashing is not visible. The program is shown in Figure 6.

Close

When the ENM or ENS pin is pulled down by 0.5 milliseconds or longer, the corresponding display channel is closed, and when the next ENM or ENS enters the high edge, the light is tuned, Reset to 100%. When ENM and ENS are pulled down 0.5 milliseconds or longer, the A8434 enters the closed mode.

Short -circuit protection

A8434 has the protection of short -circuited output. When the external voltage is lower than 1.2V, the integrated circuit enters the short -circuit mode. After the short circuit is eliminated, the A8434 resumes normal work.

Overvoltage protection

A8434 has a power supply voltage of up to 4.9 V to prevent unexpected overvoltage caused by LED. When any LED is opened, VOUT will be increased to 6 V. The remaining LEDs will continue to work normally. After the failure is eliminated, it will return toWork normally.

LED broken line

Each LEDX pin has a disabled circuit, as shown in Figure 7.A8434 compares the voltage on each LED tube foot. If the voltage on the foot is greater than VOUT -0.4 V or VIN -0.4 V, the corresponding LED tube foot is disabled.

If no WLED is used, the corresponding pins are connected to VOUT.Don't open any unused WLED tube.When it is connected to VOUT and the corresponding LED group (master or deputy) is enabled, the LED tube foot usually sinks 20 μA.

Note: In the shutdown mode (enm ENS 0V GT; 0.5ms), the total leakage current lt; 1 μA.

Hot shutdown

Excessive protection inside IC.The overheating limit is set to 165 ° C nominal value.When the knot temperature exceeds 165 ° C, the IC is turned off and automatically opened when IC cools.

Component selection

It is recommended to use X5R or X7R medium in the input capacitors, CIN, output capacitors, COUT and charge pump capacitors C1 and C2.

ES package, 3 × 3 mm 16 -pin qfn/mlp