MAX5057AASA Ver la hoja de datos (PDF) - Maxim Integrated

Número de pieza

componentes Descripción

Fabricante

MAX5057AASA

4A, 20ns, Dual MOSFET Drivers

Maxim Integrated 

4A, 20ns, Dual MOSFET Drivers

Supply Bypassing and Grounding

Pay extra attention to bypassing and grounding the

MAX5054–MAX5057. Peak supply and output currents

may exceed 8A when both drivers drive large external

capacitive loads in phase. Supply voltage drops and

ground shifts create forms of negative feedback for

inverters and may degrade the delay and transition times.

Ground shifts due to insufficient device grounding may

also disturb other circuits sharing the same AC ground

return path. Any series inductance in the VDD, OUT_,

and/or GND paths can cause oscillations due to the very

high di/dt when switching the MAX5054–MAX5057 with

any capacitive load. Place one or more 0.1µF ceramic

capacitors in parallel as close to the device as possible to

bypass VDD to GND. Use a ground plane to minimize

ground return resistance and series inductance. Place

the external MOSFET as close as possible to the

MAX5054–MAX5057 to further minimize board induc-

tance and AC path impedance.

Power Dissipation

Power dissipation of the MAX5054–MAX5057 consists

of three components: caused by the quiescent current,

capacitive charge/discharge of internal nodes, and the

output current (either capacitive or resistive load).

Maintain the sum of these components below the maxi-

mum power dissipation limit.

The current required to charge and discharge the internal

nodes is frequency dependent (see the Supply Current

vs. Supply Voltage graph in the Typical Operating

Characteristics). The power dissipation (PQ) due to the

quiescent switching supply current (IDD-SW) per driver

can be calculated as:

PQ = VDD x IDD-SW

For capacitive loads, use the following equation to esti-

mate the power dissipation per driver:

PCLOAD = CLOAD x (VDD)2 x fSW

where CLOAD is the capacitive load, VDD is the supply

voltage, and fSW is the switching frequency.

Calculate the total power dissipation (PT) per driver as

follows:

PT = PQ + PCLOAD

Use the following equation to estimate the MAX5054–

MAX5057 total power dissipation per driver when driving

a ground-referenced resistive load:

PT = PQ + PRLOAD

PRLOAD = D x RON(MAX) x ILOAD2

where D (duty cycle) is the fraction of the period the

MAX5054–MAX5057’s output pulls high duty cycle,

RON(MAX) is the maximum on-resistance of the device

with the output high, and ILOAD is the output load current

of the MAX5054–MAX5057.

Layout Information

The MAX5054–MAX5057 MOSFET drivers source and

sink large currents to create very fast rising and falling

edges at the gate of the switching MOSFET. The high

di/dt can cause unacceptable ringing if the trace

lengths and impedances are not well controlled. Use the

following PC board layout guidelines when designing

with the MAX5054–MAX5057:

• Place one or more 0.1µF decoupling ceramic

capacitors from VDD to GND as close to the device

as possible. Connect VDD and GND to large copper

areas. Place one bulk capacitor of 10µF (min) on

the PC board with a low resistance path to the VDD

input and GND of the MAX5054–MAX5057.

• Two AC current loops form between the device and

the gate of the driven MOSFET. The MOSFET looks

like a large capacitance from gate to source when the

gate pulls low. The active current loop is from the

MOSFET gate to OUT_ of the MAX5054–MAX5057, to

GND of the MAX5054–MAX5057, and to the source of

the MOSFET. When the gate of the MOSFET pulls

high, the active current is from the VDD terminal of the

decoupling capacitor, to VDD of the MAX5054–

MAX5057, to OUT_ of the MAX5054–MAX5057, to the

MOSFET gate, to the MOSFET source, and to the

negative terminal of the decoupling capacitor. Both

charging current and discharging current loops are

important. Minimize the physical distance and the

impedance in these AC current paths.

• Keep the device as close to the MOSFET as possible.

• In a multilayer PC board, the inner layers should

consist of a GND plane containing the discharging

and charging current loops.

• Pay extra attention to the ground loop and use a

low-impedance source when using a TTL logic-

input device. Fast fall time at OUT_ may corrupt the

input during transition.

______________________________________________________________________________________ 11

Share Link: