TOSHIBA BiCD Integrated Circuit Silicon Monolithic
TB62752AFUG
Step Up Type DC-DC Converter for White LED
The TB62752AFUG is a high efficient Step-Up Type DC-DC Converter specially designed for constant current driving of White LED.
This IC contains N-ch MOSFET Transistor for Coil-Switching, and LED current (IF) is set with an external resistor.
This IC is especially for driving back light white LEDs in LCD of PDA, Cellular Phone, or Handy Terminal Equipment.
Features
- 2-8 white LEDs connected series.
- Variable LED current IF is set with a external resistor : 20 mA (typ.) @RSENS = 15 Ω
- Output power: Available for 800 mW LED loading (VIN=2.8V, 7LEDs, IF = Over 25 mA)
- High efficiency: 80% over (using recommended external parts)
- Output over voltage shutdown function : Switching operation is shut downed when OVD terminal voltage is over 34.5 V (MIN).
- IC package: SSOP6-P-0.95B
- Switching frequency: 1.0 MHz (typ.)
Pin Assignment (top view)
Note: This IC could be destroyed in some case if amounted in 180° inverse direction. Please be careful about IC direction in mounting.
Block Diagram
Pin Function
| Pin No. | Symbol | Function Description |
|---|---|---|
| 1 | SHDN | Voltage-input terminal for IC-enable/disable LED-I F . A high input on this pin enables the IC to operate while a low input causes it to shut down. The behavior of the IC is unpredictable if the input on the pin is undefined. Ensure that the pin is tied to either a high or low level. |
| 2 | OVD | Over voltage detection terminal. IC switching operation is disabled with detection over voltage. If the voltage returns to detection level or less, operation is enabled again. |
| 3 | VIN | Supply voltage input terminal. (2.8 V to 5.5 V) |
| 4 | SW | Switch terminal for DC-DC converter. Nch MOSFET built-In. |
| 5 | GND | Ground terminal. |
| 6 | FB | LED I F setting resistor connecting terminal. |
Table Caption: This table lists the pin configuration for an integrated circuit, detailing each pin's number, symbol, and function description, which includes enable/disable, over-voltage detection, power supply input, DC-DC converter switch, ground, and LED current setting.
I/O Equivalent Pin Circuits
1. SHDN
3. VIN to GND
-
FB
-
OVD
-
SW
Usage Precautions
Protection in LED Opened Condition
The operation with OVD terminal is available for the protection in case LED circuit opened.
When the voltage of OVD terminal is over 34.5 V (MIN), Nch MOSFET switching operation is disabled in the IC. When the voltage of OVD terminal drops below 34.5 V (MIN), Nch MOSFET switching operation becomes available again.
If load of LED is detached, Nch MOSFET switching operation is disabled with detection of boost circuit voltage and the IC is protected from unexpected over voltage.
Setting of Capacitor
The recommended values are
C1 = 2.2 ( μ F) or more, C2 = 1.0 ( μ F) or moreThe capacitor of ceramic condenser tends to decrease when voltage is applied.
So, please select the appropriate capacitor in consideration of IC characteristics of withstand
