OUT

JA

A

J

OUT

V

1

1

R

T

T

I

˜

K

K

˜

T

22

LM53602-Q1, LM53603-Q1

SNVSA42B – JUNE 2015 – REVISED MAY 2016

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Table 6. Recommenced Inductors

MANUFACTURER

PART NUMBER

SATURATION

CURRENT

D.C. RESISTANCE

Würth

7440650022

6 A

15 m

Ω

Coilcraft

DO3316T-222MLB

7.8 A

11 m

Ω

Coiltronics

MPI4040R3-2R2-R

7.9 A

48 m

Ω

Vishay

IHLP2525CZER2R2M01

14 A

18 m

Ω

Vishay

IHLP2525BDER2R2M01

14 A

28 m

Ω

Coilcraft

XAL6030-222ME

16 A

13 m

Ω

9.2.2.5 VCC

The VCC pin is the output of the internal LDO, used to supply the control circuits of the LM53603-Q1. This output

requires a 3.3 µF to 4.7µF, ceramic capacitor connected from VCC to GND for proper operation. An X7R device

with a rating of 10 V is highly recommended. In general this output should not be loaded with any external

circuitry. However, it can be used to supply a logic level to the FPWM input, or for the pull-up resistor used with

the RESET output (see Figure 16 ). The nominal output of the LDO is 3.15 V.

9.2.2.6 BIAS

The BIAS pin is the input to the internal LDO. As mentioned in Input Supply Current, this input is connected to

the output, it should be protected from negative voltage transients. Such transients may occur when the output is

shorted at the end of a long PCB trace or cable. If this is likely, in a given application, then a small resistor

sized to limit the current out of the BIAS pin to <100 mA. Values in the range of 2

Ω to 5 Ω are usually sufficient.

Values greater than 5

Ω are not recommended. As a rough estimate, assume that the full negative transient will

parallel with the output to limit the transient voltage and current.

9.2.2.7 CBOOT

The LM53603-Q1 requires a "boot-strap" capacitor between the CBOOT pin and the SW pin. This capacitor

stores energy that is used to supply the gate drivers for the power MOSFETs. A ceramic capacitor of 0.47 µF,

≥6.3 V is required. A 10V rated capacitor or higher is highly recommended.

9.2.2.8 Maximum Ambient Temperature

As with any power conversion device, the LM53603-Q1 will dissipate internal power while operating. The effect of

this power dissipation is to raise the internal temperature of the converter, above ambient. The internal die

thus establishing a limit on the maximum device power dissipation and therefore load current at high ambient

temperatures. Equation 5 shows the relationships between the important parameters.

(5)

available output current. As stated in SPRA953, the values given in the Thermal Information table are not valid

for design purposes and must not be used to estimate the thermal performance of the application. The values

reported in that table were measured under a specific set of conditions that are never obtained in an actual

temperature, PCB area, copper heat-sink area, number of thermal vias under the package, air flow, and adjacent

component placement. The LM53603-Q1 utilizes an advanced package with a heat spreading pad (EP) on the

bottom. This must be soldered directly to the PCB copper ground plane to provide an effective heat-sink, as well

as a proper electrical connection. The resources found in Table 9 can be used as a guide to optimal thermal

board area is shown in Figure 17. The copper area in this graph is that for each layer of a four layer board; the