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TSZ02201-0F4F0A2BM1R0-1-2

© 2016 ROHM Co., Ltd. All rights reserved.

20. Apr. 2016 Rev.002

www.rohm.com

TSZ22111

• 15 • 001

BM1R00xxxF

0V

-100mV

-100mV

MAX_TON

TIMER

-Vf

Description of Block

– continued

5.

MAX_TON Block

MAX_TON block sets the maximum ON time. DRAIN terminal voltage starts counting when the rising edge of the

synchronous rectification FET will be forced OFF after the set time has elapsed. The time can be adjusted by varying

the resistance value of the resistor connected to the MAX_TON terminal.

Calculation Example:

However, the formula above is for an ideal approximation only; it is still strongly advised that the operation of the actual

application should still be verified.

By setting this time, it becomes possible to prevent the simultaneous ON operation of the primary side and the

secondary side in continuous mode.

The drive sequence in continuous mode operation is shown in the figure below:

in series should be connected to the MAX_TON terminal. The capacitance should approximately be 1000pF, and the

resistance value is recommended to be around

1kΩ.This also serves as phase compensation of MAX_TON terminal

and therefore should be connected.

This function may be disabled by pulling up the MAX_TON terminal to VCC pin in quasi-resonant and current

resonance applications which do not operate on conti

nuous mode. The 1000pF and 1kΩ resistor is also unnecessary.

6.

AUTO SHUTDOWN Block

The Auto Shutdown block automatically turns the synchronous rectification ON/OFF depending on the presence or

absence of the DRAIN terminal pulse. Shutdown occurs if the input pulses on the DRAIN terminal has more than 200us

between pulses. This stops the synchronous rectification operation. The IC will restart the synchronous rectification

after it detects 256 occurrences of input pulses on the DRAIN terminal.

7.

SHUNT REGULATOR Chip

A high-accuracy shunt regulator with ultra-low consumption is used for controlling the output voltage of the AC/DC.

Since the synchronous rectification and the shunt regulator are built in a completely different chip, GND separation is

possible. Therefore, it becomes possible to place the shunt regulator on the secondary-side GND reference in the

synchronous rectification applications in case of disposing the High Side FET. It can also be used as protection for the

comparator, the secondary side OVP, FET overheat protection, etc.

8.

PROTECTION Block

When an abnormal condition is detected after the timer count is completed, the photo coupler from SH_OUT terminal is

driven to stop the switching operation on the primary side.

(5) Elapsed the set time in MAX_TON terminals, the secondary-side FET = compulsory OFF.













k

s

k

µs

100

/

10

10



 

 



k

µs

t

k

R

TON

MAX

TON

MAX



/

10

_

_









(1)

(2)

(3)

(4)

(6)

(5)

(1)

to avoid concurrent ON state

at continuous mode

operation.

Primary

Side

Controller

+

-

-100mV

S

Q

R

VCCx1.4

Compulsion

ON TIME

-6mV

MAX_TON

BLOCK

MAX_TON

GND

LDO BLOCK

+

-

SR_GND

DRAIN_COMP

SET_COMP

RESET_COMP

Compulsion

OFF TIME

Np Ns

VH

Figure 2. The drive sequence in continuous mode operation