MAX5072 datasheet(20/30 Pages) MAXIM

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ESR

∆

where

(

)

L f

−×

∆=

where VDS is the total voltage drop across the internal

MOSFET plus the voltage drop across the inductor

ESR.

∆IL is the peak-to-peak inductor ripple current as

calculated above. ∆VQ is the portion of input ripple due

to the capacitor discharge and ∆VESR is the contribution

due to ESR of the capacitor.

Output Capacitor Selection

For the boost converter, the output capacitor supplies the

load current when the main switch is ON. The required

output capacitance is high, especially at higher duty

cycles. Also, the output capacitor ESR needs to be low

enough to minimize the voltage drop due to the ESR while

supporting the load current. Use the following equation to

calculate the output capacitor for a specified output ripple

tolerance.

ESR

∆

MAX

OUT

∆×

IO is the load current, ∆VQ is the portion of the ripple due

to the capacitor discharge and ∆VESR is the contribution

due to the ESR of the capacitor. DMAX is the maximum

duty cycle at minimum input voltage.

Power Dissipation

The MAX5072 includes a high-frequency, low RDS_ON

switching MOSFET. At +85°C, the RDS_ON of the internal

switch for converter 1 and converter 2 are 290mΩ and

630mΩ, respectively. The DC loss is a function of the

RMS current in the switch while the switching loss is a

function of switching frequency and input voltage. Use

the following equations to calculate the RMS current, DC

loss, and switching loss of each converter. The MAX5072

device is available in a thermally enhanced package and

can dissipate up to 2.7W at +70°C ambient temperature.

The total power dissipation in the package must be

limited so the junction temperature does not exceed its

absolute maximum rating of +150°C at maximum ambient

temperature.

For the buck converter:

MAX

RMS

DC PK

+(I

I ))

RMS

DS(ON)MAX

where

∆

−

∆

See the Electrical Characteristics table for the RDS(ON)MAX

value.

INMAX O

t ) f

××

For the boost converter:

Figure 7. Type II Compensation Network.

Figure 8. Type III Compensation Network

COMP

VOUT

VREF

CCF

COMP

VOUT

VREF

CCF

COMP

VOUT

VREF

CCF

www.maximintegrated.com

Maxim Integrated │ 20

MAX5072

2.2MHz, Dual-Output Buck or Boost

Converter with POR and Power-Fail Output

MAX5072 Datasheet(PDF) 20 Page - Maxim Integrated Products

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