LCS7260C datasheet(6/35 Pages) POWERINT

6 / 35 page

Rev. D 11/22

HiperLCS-2

www.power.com

Short fault auto-restart occurs for fault events that are detected while

operating in secondary control. This auto-restart off-period is

approximately 200 ms. All faults that trigger during primary control

result in analog auto-restart response where the off-time is around 5

seconds.

The short-auto-restart event allows quick restart for occasional faults.

The long auto-restart ensures that repetitive auto-restart maintains a

very low auto-restart-attempt versus auto-restart-off-time ratio. This

in turn ensures that the persistent fault does not create excess

electrical nor thermal stress on the part.

The primary includes many layers of device self-protection to achieve

rugged performance in the event of faults.

At power-up the device completes FMEA checks (failure-mode effect

analysis) on device pins. If faults are observed the device will not

start switching. Note that such an FMEA fault will not report an error

code on the PP pin if it occurs prior to switching. Fault reporting

messages on the PP pin are only generated for faults which occur

after switching has started.

Primary half-bridge current is internally sensed during low-side

MOSFET on-time. This is used for both primary start-up and also for

safety current limits during secondary mode.

The primary device also includes (high-side controller) over-temperature

protection. This protects against excessive power dissipation in the

primary package. The device also has ambient (low-side controller)

thermal protection, which prevents restart until the temperature has

lowered sufficiently to allow restart. This prevents thermal

temperature built up which might otherwise occur in the event of

immediate restart for repeat fault conditions. Thermal fault triggers

either latching or non-latching response (PP pin select).

The L pin detects input voltage for undervoltage and overvoltage

protection. The input voltage is coupled via a resistor connected to

L pin. The L pin is polled during burst operation to reduce system

consumption. During continuous switching (non-burst) the L pin is

continuously monitored. Overvoltage and undervoltage both have

hysteresis to prevent chatter. On exiting undervoltage the device

goes through a restart. However, for overvoltage the device switching

is blocked while the condition persists but allowed to continue when

condition is removed. Note: that the L pin detects at power-up

whether the pin is connected to ground or if there is a resistor

between the HD pin and L pin. If the L pin is connected to ground

then the PP pin power-good input function is used instead to indicate

line-UV/OV conditions.

The BPL pin provides main supply voltage into the low-side driver and

controller. This voltage is internally regulated to provide 5 V at 5VL

pin. Note: the 5VL pin is not intended to provide power to any

external devices other than the isolation device. The BPH and 5VH

pins provide similar functions on the high-side driver. Both must be

externally decoupled to ground with a capacitor.

The BPL, 5VL, BPH and 5VH pins are monitored for undervoltage

condition. At start-up the device will not begin switching until all are

above their respective UV thresholds. The pins are also monitored

during normal switching and UV will trigger auto-restart. Please note

that unlike faults, a UV-condition on BPL, 5VL, BPH, 5VH will force a

restart but will not output a fault to the PP pin.

Miscellaneous Primary Functions

At power-up, the PP pin is used to read customer configuration

(resistor) settings (see Table 2), which select for the primary start-up

frequency range (90, 120, 180, 240 kHz), and latching/non-latching

fault handling. The PP pin may also be used to receive a power-good

input signal from an external system (such as PFC controller) when

the L pin is connected to ground. As mentioned previously, when PP

pin (PG) function is used, the start-up current is set to the lower

value of I

HB(IOVL-). This is intended only for PFC-boost applications

where the I

HB(IOVL-) slows the output voltage rise and reduces output

overshoot. The same PP pin (PG) signal could be used for remote-

on/off. The PP pin can also receive an external fault signal to disable

device under fault or other conditions – this signal is handled with

latching/non-latching fault response. During fault conditions the PP

pin is also used to output device error codes to help with debug. The

error code is output as a binary non-return-to-zero (NRZ) bit stream.

LCS7260C Datasheet(PDF) 6 Page - Power Integrations, Inc.

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