TOP250 datasheet(5/54 Pages) POWERINT

5 / 54 page

Rev. R 10/20

TOP242-250

www.power.com

TOPSwitch-GX Family Functional

Description

Like TOPSwitch, TOPSwitch-GX is an integrated switched

mode power supply chip that converts a current at the

control input to a duty cycle at the open drain output of a

high voltage power MOSFET. During normal operation the

duty cycle of the power MOSFET decreases linearly with

increasing CONTROL pin current as shown in Figure 7.

In addition to the three terminal TOPSwitch features, such as

the high voltage start-up, the cycle-by-cycle current limiting,

loop compensation circuitry, auto-restart, thermal shutdown,

the TOPSwitch-GX incorporates many additional functions that

reduce system cost, increase power supply performance and

design flexibility. A patented high voltage CMOS technology

allows both the high voltage power MOSFET and all the low

voltage control circuitry to be cost effectively integrated onto a

single monolithic chip.

Three terminals, FREQUENCY, LINE-SENSE, and EXTERNAL

CURRENT LIMIT (available in Y, R or F package) or one

terminal MULTI-FUNCTION (available in P or G package)

have been added to implement some of the new functions.

These terminals can be connected to the SOURCE pin

to operate the TOPSwitch-GX in a TOPSwitch-like three

terminal mode. However, even in this three terminal mode,

the TOPSwitch-GX offers many new transparent features

that do not require any external components:

1. A fully integrated 10 ms soft-start limits peak currents

and voltages during start-up and dramatically reduces

or eliminates output overshoot in most applications.

2. DC

MAX of 78% allows smaller input storage capacitor,

lower input voltage requirement and/or higher power

capability.

3. Frequency reduction at light loads lowers the switching

losses and maintains good cross regulation in multiple

output supplies.

4. Higher switching frequency of 132 kHz reduces the

transformer size with no noticeable impact on EMI.

5. Frequency jittering reduces EMI.

6. Hysteretic over-temperature shutdown ensures

automatic recovery from thermal fault. Large hysteresis

prevents circuit board overheating.

7. Packages with omitted pins and lead forming provide

large drain creepage distance.

8. Tighter absolute tolerances and smaller temperature

variations on switching frequency, current limit and

PWM gain.

The LINE-SENSE (L) pin is usually used for line sensing by

connecting a resistor from this pin to the rectified DC high

voltage bus to implement line overvoltage (OV), under-

voltage (UV) and line feed-forward with DC

MAX reduction. In

this mode, the value of the resistor determines the OV/UV

thresholds and the DC

MAX is reduced linearly starting from a

line voltage above the undervoltage threshold. See Table 2

and Figure 11.

The pin can also be used as a remote ON/OFF and a

synchronization input.

The EXTERNAL CURRENT LIMIT (X) pin is usually used to

reduce the current limit externally to a value close to the

operating peak current, by connecting the pin to SOURCE

through a resistor. This pin can also be used as a remote

ON/OFF and a synchronization input in both modes. See

Table 2 and Figure 11.

For the P or G packages the LINE-SENSE and EXTERNAL

CURRENT LIMIT pin functions are combined on one

MULTI-FUNCTION (M) pin. However, some of the functions

become mutually exclusive as shown in Table 3.

The FREQUENCY (F) pin in the Y, R or F package sets the

switching frequency to the default value of 132 kHz when

connected to SOURCE pin. A half frequency option of

PI-2633-011502

C (mA)

TOP242-5 1.6 2.0

TOP246-9 2.2 2.6

TOP250

2.4 2.7

5.2 6.0

5.8 6.6

6.5 7.3

CD1

Auto-restart

L = 125 µA

L < IL(DC)

L = 190 µA

C (mA)

CD1

Auto-restart

132

Note: For P and G packages I

L is replaced with IM.

L < IL(DC)

L = 125 µA

Slope = PWM Gain

L = 190 µA

Figure 7. Relationship of Duty Cycle and Frequency to CONTROL

Pin Current.

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