MP1400 – NEGATIVE DCDC POWER CONVERTER

MP1400 Rev.1.1

www.MonolithicPower.com

13

5/27/2015

MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.

© 2015 MPS. All Rights Reserved.

Additional output capacitance may also be

required to reduce ripple in DCM mode and to

ensure stability in PWM mode, especially at

higher output load current.

Power Dissipation

IC power dissipation plays an important role in

circuit design—not only because of efficiency

concerns, but also because of the chip’s thermal

requirements.

Several

parameters

influence

power dissipation, such as:

Conduction Loss (Cond)

Dead time (DT)

Switching Loss (SW)

MOSFET Driver Current (DR)

Supply Current (S)

Based on these parameters, we can estimate the

power loss to equal:

LOSS

Cond

DT

SW

DR

S

PP

P

P

P

P









PCB Layout

Layout is important, especially for switching

power supplies with high switching frequencies;

poor layout results in reduced performance, EMI

problems, resistive loss, and even system

instability.

Following the rules below can help ensure a

stable layout design:

1. Connect the GND pin to the large ground

plane by point connect mode.

2. Put the input capacitor as close as possible

to the VIN pin while keep the GND end of the

output capacitor close to the GND end of the

input capacitor.

3. Put the cathode of the schottky close to the

SW pin and the anode of the schottky close

to the output capacitor to minimize parasitic

inductance.

4. Route SW away from sensitive analog areas

such as FB. It’s not recommended to route

SW trace under chip’s bottom side.

Notes:

7) The recommended layout is based on the Figure 3 Typical

Application circuit on the next page.

VIN

R1

GND

SW

L1

GND

C2A

R2

U1

C2B

C2C

D1

VOUT

VIN

Design Example

Below is a design example following the

application guidelines for the specifications:

Table 2: Design Example

5V

-5V

Io

0.6A

The detailed application schematic is shown in

Figure 3. The typical performance and circuit

waveforms have been shown in the Typical

Performance Characteristics section. For more

device applications, please refer to the related

Evaluation Board Datasheets.