beautypg.com

Detailed description, Typical application circuit, Controller function – Rainbow Electronics MAX15051 User Manual

Page 9

background image

MAX15050/MAX15051

C9
0.1

µF

OPTIONAL

C1

22

µF

OUTPUT

1.8V/4A

INPUT

2.9V TO 5.5V

C3

0.1

µF

BST

LX

IN

V

DD

FB

COMP

C12

56pF

C10

1000pF

C11

1500pF

R4

5.62k

R5

20k

PWRGD

L1

0.82

µH

C8

0.033

µF

C2
47

µF

R6

71.5

C4
0.01

µF

C5

2.2

µF

REFIN/SS

GND

V

DD

MAX15050
MAX15051

U1

IN

EN

ON

OFF

BST

LX

LX

R10

2.2

C15
1000pF

GND

R3
8.06k

1%

R7
4.02k

1%

High-Efficiency, 4A, 1MHz, Step-Down Regulators

with Integrated Switches in 2mm x 2mm Package

_______________________________________________________________________________________

9

Figure 1. All-Ceramic Capacitor Design with V

OUT

= 1.8V

Detailed Description

The MAX15050/MAX15051 high-efficiency, voltage-
mode switching regulators can deliver up to 4A of out-
put current. The MAX15050/MAX15051 provide output
voltages from 0.6V to (0.9 x V

IN

) from 2.9V to 5.5V input

supplies, making them ideal for on-board point-of-load
applications. The output-voltage accuracy is better than
±1% over load, line, and temperature.

The MAX15050/MAX15051 feature a 1MHz fixed switch-
ing frequency, allowing the user to achieve all-ceramic
capacitor designs and fast transient responses. The high
operating frequency minimizes the size of external com-
ponents. The MAX15050/MAX15051 are available in a
2mm x 2mm, 16-bump (4 x 4 array), 0.5mm pitch WLP
package. The REFIN/SS function makes the
MAX15050/MAX15051 ideal solutions for DDR and track-
ing power supplies. Using internal low-R

DS(ON)

(24m

and 18m

Ω) n-channel MOSFETs for the high- and low-

side switches, respectively, maintains high efficiency at
both heavy-load and high-switching frequencies.

The MAX15050/MAX15051 employ voltage-mode con-
trol architecture with a high-bandwidth (> 26MHz) error
amplifier. The op-amp voltage-error amplifier works with

type III compensation to fully utilize the bandwidth of
the high-frequency switching to obtain fast transient
response. Adjustable soft-start time provides flexibilities
to minimize input startup inrush current. An open-drain,
power-good (PWRGD) output goes high impedance
when V

FB

exceeds 92.5% of V

REFIN/SS

and V

REFIN/SS

is above 0.54V. PWRGD goes low when V

FB

falls below

90% of V

REFIN/SS

or V

REFIN/SS

is below 0.54V.

Controller Function

The controller logic block is the central processor that
determines the duty cycle of the high-side MOSFET
under different line, load, and temperature conditions.
Under normal operation, where the current-limit and
temperature protection are not triggered, the controller
logic block takes the output from the PWM comparator
and generates the driver signals for both high-side and
low-side MOSFETs. The control logic block controls the
break-before-make logic and the timing for charging
the bootstrap capacitors. The error signal from the volt-
age-error amplifier is compared with the ramp signal
generated by the oscillator at the PWM comparator to
produce the required PWM signal. The high-side switch
turns on at the beginning of the oscillator cycle and

Typical Application Circuit