TOP232 datasheet(4/38 Pages) POWERINT

4 / 38 page

Rev. D 10/20

TOP232-234

www.power.com

TOPSwitch-FX Family Functional Description

Figure 4. Relationship of Duty Cycle to CONTROL Pin Current.

PI-2504-072799

C (mA)

M = 140 µA

M = 190 µA

M < IM(DC)

1.9

1.5

5.5 5.9

Slope = PWM Gain

CD1

Auto-restart

1.5

Like TOPSwitch, TOPSwitch-FX 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 4.

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,

etc., the TOPSwitch-FX 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.

Two terminals, FREQUENCY (available only in Y package) and

MULTI-FUNCTION, have been added to implement some of

the new functions. These terminals can be connected to the

SOURCE pin to operate the TOPSwitch-FX in a TOPSwitch-

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

mode, the TOPSwitch-FX offers many new transparent

features that do not require any external components:

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

and voltages during start-up and practically 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. Cycle skipping at minimum pulse width achieves regulation

and very low power consumption at no load.

4. Higher switching frequency of 132 kHz reduces the

transformer size with no noticeable impact on EMI or on

high line efficiency.

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 vari-

ations on switching frequency, current limit and PWM gain.

The MULTI-FUNCTION pin is usually used for line sensing by

connecting a resistor from this pin to the rectified DC high-

voltage bus to implement line over-voltage (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 under-voltage threshold. In high efficiency applications, this

pin can be used in the external current limit mode instead, to

reduce the current limit externally (to a value close to the

operating peak current), by connecting the pin to SOURCE

through a resistor. The same pin can also be used as a

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

The FREQUENCY pin in the TO-220 package sets the

switching frequency to the default value of 132 kHz when

connected to SOURCE pin. A half frequency option can be

chosen by connecting this pin to CONTROL pin instead.

Leaving this pin open is not recommended.

CONTROL (C) Pin Operation

The CONTROL pin is a low impedance node that is capable of

receiving a combined supply and feedback current. During

normal operation, a shunt regulator is used to separate the

feedback signal from the supply current. CONTROL pin

voltage V

C is the supply voltage for the control circuitry

including the MOSFET gate driver. An external bypass

capacitor closely connected between the CONTROL and

SOURCE pins is required to supply the instantaneous gate

drive current. The total amount of capacitance connected to

this pin also sets the auto-restart timing as well as control loop

compensation.

When rectified DC high-voltage is applied to the DRAIN pin

during start-up, the MOSFET is initially off, and the CONTROL

pin capacitor is charged through a switched high-voltage

current source connected internally between the DRAIN and

CONTROL pins. When the CONTROL pin voltage V

C reaches

approximately 5.8 V, the control circuitry is activated and the

soft-start begins. The soft-start circuit gradually increases the

duty cycle of the MOSFET from zero to the maximum value

over approximately 10 ms. If no external feedback/supply

current is fed into the CONTROL pin by the end of the

soft-start, the high-voltage current source is turned off and the

CONTROL pin will start discharging in response to the supply

current drawn by the control circuitry. If the power supply is

designed properly, and no fault condition such as open loop or

shorted output exists, the feedback loop will close, providing

external CONTROL pin current, before the CONTROL pin

voltage has had a chance to discharge to the lower threshold

voltage of approximately 4.8 V (internal supply under-voltage

lockout threshold). When the externally fed current charges the

CONTROL pin to the shunt regulator voltage of 5.8 V, current

TOP232 数据表(PDF) 4 Page - Power Integrations, Inc.

TOP232 数据表(HTML) 4 Page - Power Integrations, Inc.

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38

数据表下载