 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
CM9153-01MR Datasheet(PDF) 7 Page - California Micro Devices Corp |
|
||||||||||||||||||||||||||||||
CM9153-01MR Datasheet(HTML) 7 Page - California Micro Devices Corp |
|
|
7 / 12 page  © 2006 California Micro Devices Corp. All rights reserved. 04/26/06 490 N. McCarthy Blvd., Milpitas, CA 95035-5112 l Tel: 408.263.3214 l Fax: 408.263.7846 l www.cmd.com 7 CM9153 PRELIMINARY The CM9153 is a switched capacitor, charge pump voltage converter ideally suited for driving white LEDs to backlight or sidelight LCD color displays for portable devices, such as cellular phones, PDAs, and any appli- cation where small space and efficiency are critical. The CM9153 charge pump is the perfect driver for such portable applications by providing efficiency, compact overall size, low system cost and minimal EMI. The CM9153 contains a linear low dropout (LDO) regu- lator followed by a 1.5x fractional charge pump that converts the nominal lithium-ion (Li-Ion) or lithium poly- mer battery voltage levels (3.6V) by a gain of 1.5 and regulates the converted voltage to 4.5V, ±-5%, enough to drive the forward voltage drop of white LEDs. The CM9153 requires only two external switched, or bucket, capacitors, plus an input and an output capaci- tor resulting in a compact, low profile design. In many applications, all these can conveniently be the same value, 1.0 μF, commonly available in a compact 0805 surface mount package. The CM9153 is intended for white LED applications, but it can drive most all types of LEDs with a forward voltage drop of less than 4V. The LED current is determined by its series resistor, RLED, and is approximately: Typical white LEDs have a forward voltage drop, VFWD_LED, of 3.5V to 3.7V. Like all single junction devices, white LEDs often have poorly matched for- ward voltages. If the LEDs were put in parallel without a series resistor, the current in the paralleled branches would vary, resulting in non-uniform brightness. RLED, in addition to setting the current, compensates for this variation by functioning as a ballast resistor, providing negative feedback for each paralleled LED. CM9153 Operation When a voltage exceeding the undervoltage lockout threshold (UVLO) is applied to the VIN pin, the CM9153 initiates a softstart cycle, typically lasting 100 μS. Softstart limits the inrush current while the out- put capacitors are charged during the power-up of the device. The input voltage, VIN, passes through an LDO pre- regulator that compares the output voltage to a preci- sion bandgap reference. After the LDO, the charge pump boosts the LDO voltage by 1.5 times. A feedback circuit to the LDO monitors the output voltage, and when the output voltage reaches 4.5V, the LDO output will operate at about 3V, regulating the device output at 1.5 x 3V = 4.5V. The charge pump uses two phases from the oscillator to drive internal switches that are connected to the bucket capacitors, C1 and C2, as shown in Figure 1. In the first switch position, the bucket capacitors are con- nected in series and each are charged from the LDO to a voltage of VLDO/2. The next phase changes the switch positions so that C1 and C2 are put in parallel, and places them on top of VLDO. The resulting voltage across COUT is then; VLDO+1/2VLDO = 1.5 x VLDO. Figure 1. Switch Operation LED LED _ FWD LED R V V 5 . 4 I − = Charge C1 and C2 to ½ V LDO LDO VIN FB C1 C2 ½VLDO VLDO VOUT ½VLDO Transfer ½ VLDO charge to top of V LDO LDO VIN FB C1 C2 ½VLDO VLDO ½VLDO C OUT VOUT C OUT Application Information |
Similar Part No. - CM9153-01MR |
|
Similar Description - CM9153-01MR |
|
|
|
Link URL |
| Privacy Policy |
| ALLDATASHEET.COM |
| Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
| Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
|
Family Site : ic2ic.com |
icmetro.com |
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
