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DataSheet.in
Beyond Innovation Technology Co., Ltd.
BIT3251
BIT3251
Low Cost PWM Controller
Version: A0
Please read the notice stated in this preamble carefully before accessing any contents of the document attached. Admission of BiTEK's statement therein is presumed once the document is released to the receiver.

BiTEK
May 16, 2007
DCC CONTROLLED
2006/7/7
Confidential, for authorized user only
page 1 of 7
DOC NO.W-DS-0034
DataSheet.in
Beyond Innovation Technology Co., Ltd.
BIT3251
Notice: Firstly, the information furnished by Beyond Innovation Technology Co. Ltd. (BiTEK) in this document is believed to be accurate and reliable and subject to BiTEK's amendment without prior notice. And the aforesaid information does not form any part or parts of any quotation or contract between BiTEK and the information receiver. Further, no responsibility is assumed for the usage of the aforesaid information. BiTEK makes no representation that the interconnect of its circuits as described herein will not infringe on exiting or future patent rights, nor do the descriptions contained herein imply the granting of licenses to make, use or sell equipment constructed in accordance therewith. Besides, the product in this document is not designed for use in life support appliances, devices, or systems where malfunction of this product can reasonably be expected to result in personal injury. BiTEK customers' using or selling this product for use in such applications shall do so at their own risk and agree to fully indemnify BiTEK for any damage resulting from such improper use or sale. At last, the information furnished in this document is the property of BiTEK and shall be treated as highly confidentiality; any kind of distribution, disclosure, copying, transformation or use of whole or parts of this document without duly authorization from BiTEK by prior written consent is strictly prohibited. The receiver shall fully compensate BiTEK without any reservation for any losses thereof due to its violation of BiTEK's confidential request. The receiver is deemed to agree on BiTEK's confidential request therein suppose that said receiver receives this document without making any expressly opposition. In the condition that aforesaid opposition is made, the receiver shall return this document to BiTEK immediately without any delay. -Version A4

BiTEK
May 16, 2007
DCC CONTROLLED
2006/7/7
Confidential, for authorized user only
page 2 of 7
DOC NO.W-DS-0034
DataSheet.in
Beyond Innovation Technology Co., Ltd.
BIT3251
Pin Layout:
VDD EA CMP INN 1 8 OUT GND NC OVP 5
Features:
Voltage Mode PWM Controller Low 0.2V reference Voltage 330KHz Operation Over Voltage Protection Internal Soft-Start Internal UVLO (Under Voltage Lock Out) Limited Output Duty Cycle Low Shutdown current (0.1uA) CMOS Totem Pole Output SOP-8 Package
4
Absolute Ratings: (if Ta=25)
VDD.............................................-0.3 ~ +8 V GND............................................0.3 V Input Voltage..................................-0.3 ~ VDD+0.3 V Operating Ambit Temperature.............0 ~ 70 Extreme Operating Ambient Temp......-40 ~ 85 *** Operating Junction Temperature........+150 Storage Temperature........................-55~ 150
General Description:
The BIT3251 is a high frequency PWM controller integrates required functions for boost conversion in a small SOP-8 package. A low 0.2V feedback voltage and over voltage protection make the BIT3251 be an ideal controller for LED backlight supplies. CMOS process greatly reduces the operating current when comparing to similar products.
Recommended Operating Condition:
Supply Voltage..................................4~ 8 V Operating Frequency..........................330KHz Operating Ambient Temperature............0 ~ 70
Functional Block Diagram:
EA OVP GND
VDD = 4.0V ~ 8.0V
Band Gap Voltage References
EA HV ERR_OVP OVPN EHV
EAN EA
UVLO
4.0V
3.6V
HV
+
ERR_OVP LATCH
1.5V
-
1.75V EHV OVPN RAMP CMP
+ + -
PWMOUT
Digital Control Circuit
BUFFER
OUT
6.75K
7.05K
PWM Comparator 0.308V 1.8V
0.2V
0.75K
+ 0.45K
Error Amplifier
RAMP
Ramp Wave Generator
INN
CMP
VDD

BIT3251
BiTEK
May 16, 2007
*** For Extreme Operating Ambient Temperature, the supply voltage should be limited. from 4.5V to 7.5V.
The recommended voltage range is
DCC CONTROLLED
2006/7/7
Confidential, for authorized user only
page 3 of 7
DOC NO.W-DS-0034
DataSheet.in
Beyond Innovation Technology Co., Ltd.
BIT3251
Pin Description:
Pin No. 1 2 3 4 5 6 7 8 Names VDD EA CMP INN OVP NC GND OUT Description Supply voltage input. Enable Control Pin The output of the error amplifier. CMP is force to low when VDD < 3.6V. PWM controller input, the inverting input of error amplifier. INN is pulled high to reduce the CMP when VDD < 3.6V Over Voltage detection pin No Connection Ground Output pin
Function Description:
The PWM Controller: The pulse width modulation control circuit includes a ramp wave generator, an error amplifier and a comparator. These devices provide the required active components for the PWM feedback control application. The inverting input of the error amplifier is pulled high to reduce its output CMP when VDD<3.6V. The maximum duty cycle of the PWM controller is limited to 93% The Over Voltage Protection: The converter output voltage will boost too high when the LEDs are disconnected from the circuit or fail open. The BIT3251 will latch off the output if the OVP pin senses a voltage that is larger than 1.5V. The latched off status can be reset by reducing the supply voltage to lower than 3.6V. UVLO: The Under-Voltage-Lock-Out circuit turns the output driver off when supplying voltage drops to less than 3.6V Enable Control: When V(EA) is1.2V, the BIT3251 is enabled. When V(EA) is0.8V, the BIT3251 enter into shutdown mode operation. The BIT3251 has an internal 80K15% ohm pull low resistor on the EA pin, thus the device is normally in the OFF state or shutdown mode operation. Initial Setting: System will have a fast transition response by setting a suitably initial voltage. The BIT3251 will set an initial voltage of Vinn and Vcmp under below conditions. Table 1. Initial setting Voltage
Voltage Setting(@5V) VEA VDD VOVP VINN =0.68V, VCMP =0.53V VEA > 1.2V VINN =0.68V, VCMP =0.53V VEA < 0.8V VINN =0.68V, VCMP =0.53V VEA > 1.2V VDD < 3.6V VOVP < 1.5V VDD > 4.0V VOVP < 1.5V VDD > 4.0V VOVP > 1.5V
Setting Equation
VINN =0.68V+0.12V*(VDD-5) VCMP =0.53V+0.08V*(VDD-5)
Vcmp Vinn Vcmp
(1) (2)
Vinn=0.2V
Initial start up time
Figure 1. Initial transition response (VDD=5V, VINN =0.68V, VCMP =0.53V)

BiTEK
May 16, 2007
DCC CONTROLLED
2006/7/7
Confidential, for authorized user only
page 4 of 7
DOC NO.W-DS-0034
DataSheet.in
Beyond Innovation Technology Co., Ltd.
BIT3251
Test Conditions Measured with shorted INN CMP pins VDD=5V, Ta=25C VDD=4 ~ 8V, Ta=25C Ta=25C Note2 3.6 0.1 300 Note 1 1.7 0.25 60 1 1.45 1.2 0.8 50 90 93 65.5 88.5 95 Min. Typ.(Limits) Max. Unit
DC/AC Characteristics:
Parameter Reference Voltage Output voltage Line regulation Under Voltage Look Out Upper threshold voltage Hysteresis Ramp Wave Generator Frequency Output peak (Internal ) Output valley (Internal) Error Amplifier Open loop gain Unit gain band width Over Voltage Protection OVP threshold voltage Enable Control Turn on Threshold Turn off Threshold Output CMOS output impedance Maximum Duty Cycle Rising Time Falling Time Note 1, Note 2 VDD=5V, Ta=25C, 330KHz. VDD=5V, 1000pF load, Note 1, Note 2 % ns ns VDD=5V, Note 1 V V VDD=5V, Ta=25C 1.55 1.65 V Note 1 80 1.5 dB MHz 330 1.8 0.308 360 1.9 0.35 KHz V V 3.8 0.2 4.0 0.3 V V 0.194 0.2 2 0.206 20 V mV
Ta: ambient temperature. Note 1. Only guaranteed by simulation or sampled evaluation during -40~+85C. Note 2. The voltages of the output drivers are pulled to GND in each off states.
Not 100% tested.
Layout Notice:
Some of the pins are very sensitive to noise. Please follow the bellowing guideline to make the layout: Note 1. Please keep the capacitor between VDD and GND as close as possible. Noisy IC VDD may trigger UVLO. Note 2. Figure 2 is an example of making shortest traces between VDD and GND. The layout traces are under the IC.
VDD EA CMP INN
1
8 OUT GND NC OVP 5

BiTEK
May 16, 2007
4
DCC CONTROLLED
Figure 2
2006/7/7
Confidential, for authorized user only
page 5 of 7
DOC NO.W-DS-0034
DataSheet.in
Beyond Innovation Technology Co., Ltd.
BIT3251
Soldering Information
Reflow Soldering:
The choice of heating method may be influenced by plastic QFP package). If infrared or vapor phase heating is used and the package is not absolutely dry (less than 0.1% moisture content by weight), vaporization of the small amount of moisture in them can cause cracking of the plastic body. Preheating is necessary to dry the paste and evaporate the binding agent. Preheating duration: 45 minutes at 45 C. Reflow soldering requires solder paste (a suspension of fine solder particles, flux and binding agent) to be applied to the printed-circuit board by screen printing, stenciling or pressure-syringe dispensing before package placement. Several methods exist for reflowing; for example, convection or convection/infrared heating in a conveyor type oven. Throughput times (preheating, soldering and cooling) vary between 100 and 200 seconds depending on heating method. Typical reflow peak temperatures range from 215 to 270 C depending on solder paste material. The top-surface temperature of the packages should preferable be kept below 245 C for thick/large packages (packages with a 3 thickness 2.5 mm or with a volume 350 mm so called thick/large packages). The top-surface temperature of the packages should preferable be kept below 260 C for thin/small packages (packages with a thickness < 2.5 mm 3 and a volume < 350 mm so called thin/small packages). Stage 1'st Ram Up Rate Preheat 2'nd Ram Up Solder Joint Peak Temp Ram Down rate Condition max3.0+/-2/sec 150~200 max3.0+/-2/sec 217 above 260 +0/-5 6/sec max Duration 60~180 sec 60~150 sec 20~40 sec -
Temp ()
260 217 200 150
25 RT
60~ 180
60~150
Time(sec)
Wave Soldering:
Conventional single wave soldering is not recommended for surface mount devices (SMDs) or printed-circuit boards with a high component density, as solder bridging and non-wetting can present major problems. B i T E K
Manual Soldering:
May 16, 2007
Fix the component by first soldering two diagonally-opposite end leads. Use a low voltage (24 V or less) soldering iron applied to the flat part of the lead. Contact time must be limited to 10 seconds at up to 300 C. When using a DCC CONTROLLED dedicated tool, all other leads can be soldered in one operation within 2 to 5 seconds between 270 and 320 C.
2006/7/7
Confidential, for authorized user only
page 6 of 7
DOC NO.W-DS-0034
DataSheet.in
Beyond Innovation Technology Co., Ltd.
BIT3251
Order Information:
BIT3251-SO
SO: SOP Part number Beyond Innovation Technology Co., Ltd.
Package Information : Unit: mm SOP type :

BiTEK
May 16, 2007
DCC CONTROLLED
2006/7/7
Confidential, for authorized user only
page 7 of 7
DOC NO.W-DS-0034

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