13

KB3302

Kingbor Technology Co.,Ltd

TEL:(86)0755-26508846 FAX:(86)0755-26509052

APPLICATIONS INFORMATION

frequency. However it reduces the phase margin. The

values of R

3

and C

4

can be determined empirically by

observing the inductor current and the output voltage

during load transient. Compensation is optimized when

the largest R

3

and the smallest C

4

without producing

ringing or excessive overshoot in its inductor current and

output voltage are found.

C

5

adds a feedforward zero to the loop response. In some

cases it improves the transient speed of the converter. C

6

rolls off the gain at high frequency. This helps to stabilize

the loop. C

5

and C

6

are often not needed.

Board Layout Considerations

In a step-up switching regulator, the output filter capacitor,

the main power switch and the rectifying diode carry

switched currents with high di/dt. For jitter-free operation,

the size of the loop formed by these components should

be minimized. Since the power switch is integrated inside

the KB3302, grounding the output filter capacitor next to

the KB3302 ground pin minimizes size of the high di/dt

current loop. The input bypass capacitors should also be

placed close to the input pins. Shortening the trace at the

SW node reduces the parasitic trace inductance. This not

only reduces EMI but also decreases the sizes of the

switching voltage spikes and glitches.

Figure 9 shows how various external components are placed

around the KB3302. The frequency-setting resistor should

be placed near the ROSC pin with a short ground trace

on the PC board. These precautions reduce switching

noise pickup at the ROSC pin.

To achieve a junction to ambient thermal resistance (

θ

JA

)

of 40°C/W, the exposed pad of the KB3302 should be

properly soldered to a large ground plane. Use only 12mil

diameter vias in the ground plane if necessary. Avoid using

larger vias under the device. Molten solder may seep

through large vias during reflow, resulting in poor adhesion,

poor thermal conductivity and low reliability.

Typical Application Circuits

Figure 10(a). 1.35 MHz All Ceramic Capacitor 5V to 12V Boost

Converter. Pinout Shown is for MSOP-8

C1

2.2

µF

5V

VIN

VOUT

KB3302

2

3

1

5

6

4

GND

SHDN

SS

IN

SW

FB

ROSC

COMP

8

7

ON

OFF

C3

10BQ015

R4

D1

L1

C2

10

µF

47nF

R2

20K

R1

174K

12V, 0.7A

C4

R3

C6

All Capacitors are Ceramic.

MSOP-8 Pinout

f / MHz R

3

/ K

Ω R

4

/ K

Ω C

4

/ pF

C

6

/ pF

L

1

/

µH

0.7

22.1

22.1

2200

-

10.5

(Falco D08019)

1.35

30.9

9.31

820

-

4.7

(Falco D08017)

2

63.4

4.75

470

22

3.3

(Coilcraft DO1813P)

Efficiency

50

55

60

65

70

75

80

85

90

95

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Load Current (A)

4.7

µH, 1.4MHz

10.5

µH, 700KHz

3.3

µH, 2MHz