uP9303

6

uP9303-DS-F0101, Aug. 2017

www.upi-semi.com

200kHz switching frequency. When a resistor is connected

from FSET/SYN to ground, the uP9303 operates at a

frequency higher than 200kHz. When a resistor is

connected from FSET/SYN to VCC, the uP9303 operates

at a frequency lower than 200kHz. The Figure 2 shows the

relationship between switching frequency and the external

resistance.

R

)

k

(

)

200

F

(

9600

R

SW

FSET

Ω

−

=

R

)

(

)

200

(

48000

Ω

−

=

k

F

R

SW

FSET

10

100

1000

10

100

1000

Figure 2. Switching Frequency vs. FSET/SYN Resistance

The switching frequency can also be synchronized to

external clock from 50kHz to 500MHz applied to FSET/

SYN pin.

Figure 4 depicts the clock logic of uP9303. When a resistor

R

V

2.0V and 3.0V for 30us, the internal clock is selected for

operation (Local Clock Mode, LCM).

A Schmitt trigger circuit receives the V

generates a inverse squarewave that is synchronized to

the V

applied. The uP9303 works with synchronization mode if

the squarewave frequency is higher than 50kHz (Remote

Clock Mode RCM). The V

circuit are 2/3 and 1/3 of V

If the V

for 30us, the uP9303 asserts clock off and turns off the

converter (Clock Off Mode COM).

The transitions from LCM to COM, COM to RCM or LCM

to RCM are allowable. However, the transitions from COM

to LCM, RCM to COM or RCM to LCM are regarded as

fatal faults and not allowed. The uP9303 shuts down and

latches off when forbidden mode transitions occur and can

only be rest by POR of V

The uP9303B outputs a clock signal at CLK pin that is

be used as synchronization for other uPI controller that

features FSET/SYN pin.

Output Voltage Setting

The output voltage can be programmed by a resistive

divider connected to the FB pin as shown in the Typical

Application Circuit:

1

R

2

R

1

R

V

6

.

0

V

OUT

+

×

=

Overcurrent Protection (OCP)

The uP9303 monitors the voltage drop across the upper

MOSFET for over current protection (OCP). A resistor

connected between OCSET pin and the drain of the upper

MOSFET programs the OCP threshold level as shown in

the Figrue 3. An internal 200uA current source flows through

the R

OCSET

IN

OCSET

R

uA

200

V

V

×

−

=

PHASE

OCSET

OCP

comparator

200uA

Figure 3. OCP Level Programming.

The OCP comparator compares the V

for over current protection when the upper MOSFET turns

on. If V

The OCP threshold level is given by:

)

ON

(

DS

OCSET

)

ON

(

DS

OCSET

OCSET

OCP

R

R

uA

200

R

R

I

I

×

=

×

=

Functional Description