VIN

VIN

EN

BOOST

SW

FB

GND

VOUT

C3

L1

C2

R1

R2

D1

ON

OFF

D2

D3

C1

R3

LM2736

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SNVS316H – SEPTEMBER 2004 – REVISED DECEMBER 2014

8.2.5 LM2736X (1.6 MHz) VBOOST Derived from Series Zener Diode (VOUT) 15 V to 9 V / 750 mA

Figure 25.

8.2.5.1 Design Requirements

In applications where both VIN and VOUT are greater than 5.5 V, or less than 3 V, CBOOST cannot be charged

directly from these voltages. If VIN and VOUT are greater than 5.5 V, CBOOST can be charged from VOUT minus a

zener voltage by placing a zener diode D3 in series with D2.

8.2.5.2 Detailed Design Procedure

Table 5. Bill of Materials for Figure 25

PART ID

PART VALUE

PART NUMBER

MANUFACTURER

U1

750mA Buck Regulator

LM2736X

TI

C1, Input Cap

10µF, 25V, X7R

C3225X7R1E106M

TDK

C2, Output Cap

22µF, 16V, X5R

C3216X5R1C226M

TDK

C3, Boost Cap

0.01µF, 16V, X7R

C1005X7R1C103K

TDK

D1, Catch Diode

0.4VF Schottky 1A, 30VR

SS1P3L

Vishay

D2, Boost Diode

1VF @ 50mA Diode

1N4148W

Diodes, Inc.

D3, Zener Diode

4.3V 350mw SOT

BZX84C4V3

Diodes, Inc.

L1

6.8µH, 1.6A,

SLF7032T-6R8M1R6

TDK

R1

61.9k

Ω, 1%

CRCW06036192F

Vishay

R2

10k

Ω, 1%

CRCW06031002F

Vishay

R3

100k

Ω, 1%

CRCW06031003F

Vishay

Please refer to Detailed Design Procedures.

8.2.5.3 Application Curves

Please refer to Application Curves

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