AN3233

Main characteristics and circuit description

Doc ID 17595 Rev 1

7/35

Figure 2.

Burst mode circuit block diagram

amplified by TSC101, a dedicated high side current sense amplifier; its output is compared

to a set reference by the TSM1014; if the output load is high, the signal fed into the CC- pin

is above the reference voltage, CC_OUT stays down and the optocoupler transistor pulls up

the L6599A’s STBY pin to the RFMIN voltage (2 V), setting continuous switching operation

(no burst mode); if load decreases, the voltage on CC- falls below the set threshold,

CC_OUT goes high opening the connection between RFMIN and STBY and so allowing

burst mode operation by the L6599A.

allowed, based on the efficiency goal. The second limitation is imposed by the necessity to

feed a reasonable voltage signal into the TSM1014A inverting input. In fact, signals which

are too small would affect system accuracy.

V.

The actual value of the mounted resistor is 2 m

Ω, corresponding to P

losses at full load. The actual resistor value at burst mode threshold current provides an

obtained as follows:

Comp.

+

-

L6599A

TSM1014

TSC101

to load

to FB optocoupler

to power transformer

Comp.

+

-

E/A.

-

+

Standby

STBY

RFMIN

CC_OUT

2V

1.24V

CC-

OUT

CC+

1.25V

V_REF

100

VP

VM

3.2mΩ

I

P

R

2

MAX

out,

MAX

loss,

MAX

CS,

=

=

1.2mΩ

C

100

V

R

BM

min

CC+,

min

CS,

=

⋅

=