UCC28050, UCC28051

UCC38050, UCC38051

SLUS515F−SEPTEMBER 2002 − REVISED MARCH 2009

2

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description (continued)

In the transition mode operation, the PWM circuit is self-oscillating with the turn-on being governed by an

inductor zero-current detector (ZCD pin) and the turn-off being governed by the current-sense comparator.

Additionally, the controller provides features such as peak current limit, default timer, overvoltage protection

(OVP) and enable.

The UCC38050 and UCC38051, while being pin compatible with other industry controllers providing similar

functionality, offer many feature enhancements and tighter specifications, leading to an overall reduction in

system implementation cost. The system performance is enhanced by incorporation of zero power detect

function which allows the controller output to shut down at light load conditions without running into overvoltage.

The device also features innovative slew rate enhancement circuits which improve the large signal transient

performance of the voltage error amplifier. The low start-up and operating currents of the device results in low

power consumption and ease of start-up. Highly accurate internal bandgap reference leads to tight regulation

of output voltage in normal and OVP conditions, resulting in higher system reliability. The enable comparator

ensures that the controller is off if the feedback sense path is broken or if the input voltage is very low.

There are two key parameteric differences between UCC38050 and UCC38051. The UVLO turn-on threshold

UCC38050 is typically 1.3 mA while for UCC38051 it is 300

µA. The higher UVLO turn-on threshold of the

threshold of UCC38051 allows the operation of the PFC chip to be easily controlled by the downsteam PWM

current for faster start-up and improved transient response when output is low either at start-up or during

transient conditions. The UCC38051 scales this source current back down to 300-

µA typical source current to

gradually increase the error voltage preventing a step increase in line currents at start-up but still provides good

transient response. The UCC38051 is suitable for multiple applications including AC adapters where a

two-stage power conversion is needed. The UCC38050 is suitable for applications such as electronic ballasts

transient response can be realized.

Devices are available in either the industrial temperature range of –40

°C to 105°C (UCC2805x) or commercial

temperature range of 0

°C to 70°C (UCC3805x). Package offerings are 8-pin SOIC (D) or 8-pin PDIP (P)

packages.

ORDERING INFORMATION

TA = TJ

UVLO Threshold

Voltage ON/OFF

gM Amplifier

Source Current

Packaged Devices(1)

TA = TJ

Voltage ON/OFF

(V)

M

Source Current

(

µA)

SOIC-8 (D)

PDIP-8 (P)

−40

°C to 105°C

15.8 / 9.7

−1300

UCC28050D

UCC28050P

−40

°C to 105°C

12.5 / 9.7

−300

UCC28051D

UCC28051P

0

°C to 70°C

15.8 / 9.7

−1300

UCC38050D

UCC38050P

0

°C to 70°C

12.5 / 9.7

−300

UCC38051D

UCC38051P

(1) D (SOIC-8) package is available taped and reeled. Add R suffix to device type (e.g.

UCC28050DR) to order quantities of 2,500 devices per reel.