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PDF US2651 Data sheet ( Hoja de datos )
| Número de pieza | US2651 | |
| Descripción | HIGH PRECISION LOW COST MCM POWER SWITCH | |
| Fabricantes | Unisonic Technologies | |
| Logotipo |  |
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UNISONIC TECHNOLOGIES CO., LTD
US2651
Preliminary
HIGH PRECISION LOW COST
MCM POWER SWITCH
CMOS IC
DESCRIPTION
The UTC US2651 is a high performance, high precision and low
cost PWM Power switch for non-isolated buck application. It
combines a dedicated current mode PWM controller and error
amplifier for low component count. UTC US2651 use UTC
proprietary frequency shuffling technique for EMI performance. And
oscillator with frequency-reduction control is implemented.
The UTC US2651 has soft start control and protection function,
such as Cycle-by-Cycle current limiting, Over Loading Protection,
Output Short-Circuit Protection, RCS short Protection, OTP, VDD
OVP, and UVLO.
FEATURES
* Power on soft-start
* Load compensation
* Built-in error amplifier
* Oscillator of fixed frequency with frequency-reduction control
* Frequency shuffling for EMI improvement
* Built-in Leading Edge Blanking (LEB)
* Cycle-by-Cycle current limiting
* Over loading protection
* Output short-circuit protection
* VDD Under Voltage Lockout with hysteresis (UVLO)
* VDD OVP
ORDERING INFORMATION
Ordering Number
Lead Free
Halogen Free
US2651L-D08-T
US2651G-D08-T
- US2651G-S08-R
Package
DIP-8
SOP-8
DIP-8
SOP-8
Packing
Tube
Tape Reel
US2651L-D08-T
(1)Packing Type
(2)Package Type
(3)Green Package
(1) T: Tube, R: Tape Reel
(2) D08: DIP-8, S08: SOP-8
(3) L: Lead Free, G: Halogen Free and Lead Free
www.unisonic.com.tw
Copyright © 2014 Unisonic Technologies Co., Ltd
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US2651
Preliminary
CMOS IC
OPERATION DESCRIPTION
The UTC US2651 is a cost effective PWM power switch optimized for off-line non-isolated buck applications
including electrical appliance and linear regulator replacement. It operates in current mode and regulates output
voltage with dedicated features. High integration can afford low cost and component count solution.
Startup Current and Start up Control
Startup current of UTC US2651 is designed to be very low so that VDD could be charged up above UVLO
threshold and starts up quickly. A large value startup resistor can therefore be used to minimize the power loss in
application.
Operating Current
The Operating current of UTC US2651 is as low as 3mA. Good efficiency is achieved with the low operating
current together with ‘Muti-mode’ control features.
Oscillator operationF
The switching frequency of UTC US2651 is internally fixed at 50KHZ. No external frequency setting components
are required for PCB design simplification.
At light load or zero load condition, most of the power dissipation in a switching mode power supply is from
switching loss on the MOSFET. The magnitude of power loss is in proportion to the switching frequency. Lower
switching frequency leads to the reduction on the power loss and thus conserves the energy. The switching
frequency is internally adjusted at light load or no load condition. The switch frequency reduces at light/no load
condition to improve the conversion efficiency. The minimum switching frequency is 400Hz.
Frequency shuffling for EMI improvement
The frequency shuffling (switching frequency modulation) is implemented in UTC US2651. The oscillation
frequency is modulated so that the tone energy is spread out. The spread spectrum minimizes the conduction band
EMI and therefore eases the system design.
Built-in error amplifier
In UTC US2651, on-chip EA (error amplifier) is implemented to regulate output voltage. Through inner resistor
divider, the VDD voltage is detected at inverter input of EA to regulate output voltage.
Load Compensation for good CV regulation
In UTC US2651, load compensation is implemented to achieve good load regulation. An offset voltage is
generated at inverter input of EA by an internal current flowing into the resister divider. The current is inversely
proportional to the voltage across pin COMP, as a result, it is inversely proportional to the output load current, thus
the output voltage can be compensated specially in zero loading condition. As the load current decreases from
full-load to no-load, the offset voltage at inverter input of EA will increase.
Current Sensing and Leading Edge Blanking
Cycle-by-Cycle current limiting is offered in UTC US2651 current mode PWM control. The switch current is
detected by a sense resistor into the CS pin. An internal leading edge blanking circuit chops off the sensed voltage
spike at initial internal power MOSFET on state so that the external RC filtering on sense input is no longer needed.
The PWM duty cycle is determined by the current sense input voltage and the EA output voltage.
Gate Drive
The internal power MOSFET in UTC US2651 is driven by a dedicated gate driver for power switch control. Too
weak the gate drive strength results in higher conduction and switch loss of MOSFET while too strong gate drive
compromises EMI.
A good tradeoff is achieved through the built-in totem pole gate design with right output strength control.
Protection Control
Good power supply system reliability is achieved with its rich protection features including Cycle-by Cycle current
limiting (OCP), Over Loading Protection, Over Voltage Protection, Output Short-Circuit Protection and Under Voltage
Lockout on VDD (UVLO).
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
5 of 6
QW-R502-B23.b
5 Page | ||
| Páginas | Total 6 Páginas | |
| PDF Descargar | [ Datasheet US2651.PDF ] | |
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