RT7310 datasheet(5/12 Pages) RICHTEK

5 / 12 page

RT7310

is a registered trademark of Richtek Technology Corporation.

DS7310-00

October

2014

www.richtek.com

PWM

tS(MIN)

5µs

Valley

Signal

PWM

tS(MIN)

Valley

Signal

PWM

Valley

Signal

tS(MIN)

PWM

Valley

Signal

tSTART

……

Figure 5. PWM Triggered Method

Protections

LED Open-Circuit Protection

In an event of output open circuit, the converter will be

shut down to prevent being damaged. Once the LED is

open-circuit, the output voltage and VZCD will rise.

When the sample-and-hold ZCD voltage (VZCD_SH)

exceeds its OV threshold (VZCD_OVP, 3.1V typ.), output

OVP will be activated and the PWM output (GD pin) will

be forced low to turn off the main switch.

LED Short-Circuit Protection

LED short-circuit protection can be achieved by

cycle-by-cycle

current

limitation,

and

will

auto-restarted when the output is recovered.

Output Diode Short-Circuit Protection

When the output diode is damaged as short-circuit, the

transformer will be led to magnetic saturation and the

main switch will suffer from a high current stress. To

avoid the above situation, an output diode short-circuit

protection is built-in. When CS voltage VCS exceeds

the threshold (VCS_SD 1.5 typ.) of the output diode

short-circuit protection, RT7310 will shut down the

PWM output (GD pin) in few cycles to prevent the

converter from damage.

VDD Under-Voltage Lockout (UVLO) and

Over-Voltage Protection (VDD OVP)

RT7310 will be enabled when VDD voltage (VDD)

exceeds rising UVLO threshold (VTH_ON, 16V typ.) and

disabled when VDD is lower than falling UVLO

threshold (VTH_OFF, 9V typ.).

When VDD exceeds its over-voltage threshold (VOVP,

27V typ.), the PWM output of RT7310 is shut down. It

will be auto-restarted when the VDD is recovered to a

normal level.

Over-Temperature Protection (OTP)

The RT7310 provides an internal OTP function to

protect the controller itself from suffering thermal stress

and permanent damage. It is not suggested to use the

function as precise control of over temperature. Once

the junction temperature is higher than the OTP

threshold (TSD, 150°C typ.), the controller will shut

down until the temperature cools down by 30°C (typ.).

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