Rainbow Electronics MAX15040 - Manual (Page 9)

MAX15040
C9
0.1
µF
OPTIONAL
C1
22 µF
OUTPUT
1.8V/4A
INPUT
2.4V TO 3.6V
C3
0.1 µF
BST
LX
IN
V DD
FB
COMP
C12
33pF
C11
820pF
R4
5.1k Ω
R5
20k Ω
PWRGD
L1
0.47 µH
C8
0.033
µF
C2
22
µF
C4
0.01
µF
C10
470pF
R6
430 Ω
C5
1 µF
R1
10 Ω
REFIN/SS
GND
V DD
MAX15040
U1
IN
EN
ON
OFF
BST
LX
LX
R10
2.2 Ω
C15
1000pF
GND
R3
8.06k
Ω
1%
R7
4.02k
Ω
1%
High-Efficiency, 4A, Step-Down Regulator with
Integrated Switches in 2mm x 2mm Package
_______________________________________________________________________________________ 9
Figure 1. All-Ceramic Capacitor Design with V OUT = 1.8V
Detailed Description
The MAX15040 high-efficiency, voltage-mode switching
regulator is capable of delivering up to 4A of output
current. The MAX15040 provides output voltages from
0.6V to (0.9 x V
IN ) from 2.4V to 3.6V input supplies,
making it ideal for on-board point-of-load applications.
The output-voltage accuracy is better than ±1% over
load, line, and temperature.
The MAX15040 features a 1MHz fixed switching frequen-
cy, allowing the user to achieve all-ceramic capacitor
designs and fast transient responses. The high operating
frequency minimizes the size of external components.
The MAX15040 is available in a 2mm x 2mm, 16-bump
(4 x 4 array), 0.5mm pitch WLP package. The REFIN/SS
function makes the MAX15040 an ideal solution for DDR
and tracking power supplies. Using internal low-R
DSON
(15m
Ω) n-channel MOSFETs for both high- and low-side
switches maintains high efficiency at both heavy-load
and high-switching frequencies.
The MAX15040 employs voltage-mode control architec-
ture with a high-bandwidth (> 15MHz) 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 mini-
mize 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 tem-
perature 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 voltage-
error amplifier is compared with the ramp signal generat-
ed 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 turns off when
the ramp voltage exceeds the V
COMP signal or the cur-
rent-limit threshold is exceeded. The low-side switch
then turns on for the remainder of the oscillator cycle.
Typical Application Circuit