MAX77231 datasheet(7/10 Pages) MAXIM

Part #	MAX77231

Description	2.75V to 4.8V Input, 10mA Output, 35μVRMS Ultra-Low Noise Boost Regulator Ultra-Small Solution Size (< 7mm2)

Download	10 Pages

Scroll/Zoom	100%

Manufacturer	MAXIM [Maxim Integrated Products]

Direct Link	https://www.maximintegrated.com/en.html

Logo

7 / 10 page

Detailed Description

The MAX77231 is a low-noise boost regulator designed

to occupy minimal PCB board space. A high-frequency

PFM boost regulator creates an 11.7V supply, which is

then post-regulated to 11.2V with a low-noise, high PSRR

PMOS linear regulator (see Figure 1). Other output volt-

ages up to 16.2V are available on request.

Boost Converter

An 11.7V (or other factory trimmed) output is generated

by a current-limited, maximum on-time, minimum off-

time, PFM boost converter. When the output drops below

11.7V, an internal NMOS switch forces the input voltage

across the inductor. The switch turns off when the inductor

current reaches 350mA, and the LX pin is driven high by

the inductor until the internal Schottky diode, D1, turns on.

Inductor current is delivered to the boost output through

the diode until the reverse inductor voltage causes the

current to drop to 0mA, and the LX voltage drops.

A maximum on-time timer prevents the LX switch from

staying on longer than 570ns if resistive, or other, losses

prevent the inductor current from reaching 350mA.

If the inductor discharge time exceeds the 35ns minimum

off time, and the BST output is still less than 11.7V, LX

switches back down to 0V, and the current builds back

up to 350mA. Under this condition, the inductor current

ramps back up before reaching 0mA, causing the boost

to operate in continuous conduction mode. This mode

is typically reached only during startup, when the BST

output is much less than 11.7V.

The typical switching frequency is:

fSW = (1/tOFF)(2 IOUT/ILPK)/Eff

where: IOUT = load current, Eff = estimated boost efficien-

cy (0.75), ILPK = inductor peak current (350mA), and tOFF

is time needed to discharge the inductor. The expression

for tOFF is:

tOFF = L x ILPK/(VBST + VDIODE - VIN)

For the typical application circuit:

tOFF = 1µH x 350mA/(11.7V + 0.4V - 3.7V) = 41.7ns

where: L = 1µH, ILPK = 350mA, VBST = 11.7V, VDIODE =

0.4V, and VIN = 3.7V, and tOFF = 41.7ns:

fSW(mA) = 183kHz/mA of load current

The MAX77231 maximum operating frequency (and

hence available output current) is governed by the charge

(tON) and discharge time (tOFF) of the inductor. tOFF is

calculated above, but is limited to at least 35ns by an

internal timer. tON is calculated below:

tON = L x ILPK/VIN

The maximum possible frequency is:

fSW(MAX) = 1/(tON + tOFF)

and consequently, typical available output current is:

IOUT(MAX) = fSW(MAX)/fSW(mA)

For a typical scenario with VIN = 3.7V, LIPK = 350mA, and

a 1µH inductor:

tON = L x ILPK/VIN = 1µH x 350mA/3.7V = 94.6ns

fSW(MAX) = 1/(tON + tOFF) = 1/(94.6ns + 41.7ns) = 7.33MHz

Typical available output current for an 11.2V output (at

OUT) and a 3.7V input is then:

IOUT(MAX) = fSW(MAX)/fSW(mA) = 7.33/0.183 = 40mA

Linear Regulator

The boost is followed by an 11.2V linear regulator. This

regulator passes the boost output current to the load,

while rejecting the unwanted ripple and reducing noise.

The linear regulator can deliver 10mA of output current

and provides 50dB of ripple rejection at 1MHz.

The linear regulator is fed from an internal low-noise

reference. The reference voltage is filtered to remove

unwanted thermal, shot, and 1/f noise generated in the

preceding circuitry. Using this low-noise reference, the

linear regulator output is able to achieve 35µVRMS noise

in a 100kHz bandwidth.

MAX77231

2.75V to 4.8V Input, 10mA Output, 35µVRMS

Ultra-Low Noise Boost Regulator

www.maximintegrated.com

Maxim Integrated │ 7

Similar Part No. - MAX77231

Manufacturer	Part #	Datasheet	Description
Maxim Integrated Produc...	MAX77231	1Mb / 10P	Output Factory-Trimmable from 11.2V to 16.2V Rev 0; 1/16
Maxim Integrated Produc...	MAX77231EVKIT	1Mb / 10P	Output Factory-Trimmable from 11.2V to 16.2V Rev 0; 1/16

More results

Similar Description - MAX77231

Manufacturer	Part #	Datasheet	Description
MPS Industries, Inc.	MPM3834C	1Mb / 20P	2.75V to 6V, 3A, Ultra-Small Power Module with Ultra-Low Noise Rev. 1.01 6/14/2022
Monolithic Power System...	MPM3814C	1Mb / 19P	2.75V to 6V, 1A, Ultra-Small Power Module with Ultra-Low Noise Rev. 1.0 4/15/2022
Monolithic Power System...	MPM3824C	1Mb / 20P	2.75V to 6V, 2A, Ultra-Small Power Module with Ultra-Low Noise Rev. 1.0 4/11/2022
Texas Instruments	ADS7040	1Mb / 42P	[Old version datasheet] Ultra-Low Power, Ultra-Small Size
Asahi Kasei Microsystem...	AK1110AEU	1Mb / 19P	2ch Output, Ultra High PSRR, Ultra Low Noise LDO Regulator
Lowpower Semiconductor ...	LP3989	610Kb / 8P	600mA,Ultra-low noise, Small Package, Ultra-Fast CMOS LDO Regulator
	LP3984	382Kb / 8P	300mA,Ultra-low noise, Small Package Ultra-Fast CMOS LDO Regulator
	LP3983S	511Kb / 8P	300mA,Ultra-low noise, Small Package Ultra-Fast CMOS LDO Regulator
	LP3982	378Kb / 8P	300mA,Ultra-low noise, Small Package Ultra-Fast CMOS LDO Regulator
	LP3981	348Kb / 8P	300mA,Ultra-low noise, Small Package Ultra-Fast CMOS LDO Regulator

More results

MAX77231 Datasheet(PDF) 7 Page - Maxim Integrated Products

MAX77231 Datasheet(HTML) 7 Page - Maxim Integrated Products

Similar Part No. - MAX77231

Similar Description - MAX77231

Html Pages

1 2 3 4 5 6 7 8 9 10

Datasheet Download

Link URL