Datasheet

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General Description

The MAX17031 is a dual Quick-PWM™ step-down

power-supply (SMPS) controller with synchronous recti-

fication, intended for main 5V/3.3V power generation in

battery-powered systems. Low-side MOSFET sensing

provides a simple low-cost, highly efficient current

sense for valley current-limit protection. Combined with

the output overvoltage and undervoltage protection fea-

tures, this current limit ensures robust output supplies.

The 5V/3.3V SMPS outputs can save power by operat-

ing in pulse-skipping mode or in ultrasonic mode to

avoid audible noise. Ultrasonic mode forces the con-

troller to maintain switching frequencies greater than

20kHz at light loads. The SKIP input also has an accu-

rate logic threshold, allowing it to be used as a sec-

ondary feedback input to refresh an external charge

pump or secondary winding without overcharging the

output voltages.

An internal 100mA linear regulator generates the 5V

bias needed for power-up or other low-power “always-

on” suspend supplies. An internal bypass circuitry

allows automatic bypassing of the linear regulator when

the 5V SMPS is active.

The device includes independent shutdown controls

with well-defined logic thresholds to simplify power-up

and power-down sequencing. To prevent current

surges at startup, the internal voltage target is slowly

ramped up from zero to the final target over a 1ms peri-

od. To prevent the output from ringing below ground in

shutdown, the internal voltage target is ramped down

from its previous value to zero over a 1ms period. A

combined power-good (PGOOD) output simplifies the

interface with external controllers. The MAX17031 is

available in a 24-pin thin QFN (4mm x 4mm) package.

Applications

Notebook Computers

Ultra-Mobile PC

Main System Supply (5V and 3.3V Supplies)

2 to 4 Li+ Cells Battery-Powered Devices

Telecommunication

Features

o Dual Quick-PWM

o Preset 5V and 3.3V Outputs

o Internal 100mA, 5V Linear Regulator

o Internal OUT1 LDO5 Bypass Switch

o Secondary Feedback (SKIP Input) Maintains

Charge Pump

o 3.3V, 5mA Real-Time Clock (RTC) Power (Always

On)

o 2V ±1% 50µA Reference

o 6V to 24V Input Range

o Pulse-Skipping/Forced-PWM/Ultrasonic Mode

Control

o Independent SMPS and LDO5 Enable Controls

o Combined SMPS PGOOD Outputs

o Minimal Component Count

MAX17031

Dual Quick-PWM Step-Down Controller with Low-

Power LDO and RTC Regulator for MAIN Supplies

________________________________________________________________

Maxim Integrated Products

*EXPOSED PAD.

*EP

ONLDO

RTC

LDO5

REF

DL2

DL1

BST2

BST1

SKIP

456

1718 16 14 13

OUT2

ILIM2

ON1

PGOOD

ILIM1

OUT1

MAX17031

GND

ON2

DH1

DH2

LX1

LX2

THIN QFN

4mm × 4mm

TOP VIEW

Pin Configuration

Ordering Information

19-4305; Rev 0; 10/08

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,

or visit Maxim’s website at www.maxim-ic.com.

EVALUATION KIT

AVAILABLE

Denotes a lead-free/RoHS-compliant package.

EP = Exposed pad.

PART TEMP RANGE PIN-PACKAGE

MAX17031ETG+ -40°C to +85°C 24 TQFN-EP*

Quick-PWM is a trademark of Maxim Integrated Products, Inc.

Summary of content (24 pages)

PAGE 1
9-4305; Rev 0; 10/08 KIT ATION EVALU E L B A IL AVA Dual Quick-PWM Step-Down Controller with LowPower LDO and RTC Regulator for MAIN Supplies o Dual Quick-PWM o Preset 5V and 3.3V Outputs o Internal 100mA, 5V Linear Regulator o Internal OUT1 LDO5 Bypass Switch o Secondary Feedback (SKIP Input) Maintains Charge Pump o 3.
PAGE 2
MAX17031 Dual Quick-PWM Step-Down Controller with LowPower LDO and RTC Regulator for MAIN Supplies ABSOLUTE MAXIMUM RATINGS IN to GND ...............................................................-0.3V to +28V VDD, VCC to GND .....................................................-0.3V to +6V RTC, LDO5, ONLDO to GND ...................................-0.3V to +6V OUT2 to GND ...........................................................-0.3V to +6V ON1, ON2, PGOOD to GND.....................................-0.
PAGE 3
Dual Quick-PWM Step-Down Controller with LowPower LDO and RTC Regulator for MAIN Supplies (Circuit of Figure 2, no load on LDO5, RTC, OUT1, OUT2, and REF, VIN = 12V, VDD = VCC = VSKIP = 5V, ONLDO = RTC, ON1 = ON2 = VCC, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 4.90 5.0 5.
PAGE 4
MAX17031 Dual Quick-PWM Step-Down Controller with LowPower LDO and RTC Regulator for MAIN Supplies ELECTRICAL CHARACTERISTICS (continued) (Circuit of Figure 2, no load on LDO5, RTC, OUT1, OUT2, and REF, VIN = 12V, VDD = VCC = VSKIP = 5V, ONLDO = RTC, ON1 = ON2 = VCC, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.
PAGE 5
Dual Quick-PWM Step-Down Controller with LowPower LDO and RTC Regulator for MAIN Supplies (Circuit of Figure 2, no load on LDO5, RTC, OUT1, OUT2, and REF, VIN = 12V, VDD = VCC = VSKIP = 5V, ONLDO = RTC, ON1 = ON2 = VCC, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX Upper SKIP/PWM threshold falling edge, 33mV hysteresis 1.94 2.0 2.06 Lower PWM/ultrasonic threshold 0.4 1.
PAGE 6
MAX17031 Dual Quick-PWM Step-Down Controller with LowPower LDO and RTC Regulator for MAIN Supplies ELECTRICAL CHARACTERISTICS (continued) (Circuit of Figure 2, no load on LDO5, RTC, OUT1, OUT2, and REF, VIN = 12V, VDD = VCC = VSKIP = 5V, ONLDO = RTC, ON1 = ON2 = VCC, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 5.15 V 260 mA -5.0 % 4.
PAGE 7
Dual Quick-PWM Step-Down Controller with LowPower LDO and RTC Regulator for MAIN Supplies (Circuit of Figure 2, no load on LDO5, RTC, OUT1, OUT2, and REF, VIN = 12V, VDD = VCC = VSKIP = 5V, ONLDO = RTC, ON1 = ON2 = VCC, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 0.2 2 V RILIM _ = 100k (VILIM _ = 500mV) 40 60 RILIM _ = 200k (VILIM _ = 1.00V) 85 115 RILIM _ = 400k (VILIM _ = 2.
PAGE 8
Typical Operating Characteristics (Circuit of Figure 1, VIN = 12V, VDD = VCC = 5V, TA = +25°C, unless otherwise noted.) EFFICIENCY (%) 85 80 12V 7V 70 20V 65 60 SKIP MODE PWM MODE 55 75 ULTRASONIC MODE 70 90 1 80 75 12V 70 65 60 60 10 7V 20V SKIP MODE PWM MODE 55 12V INPUT 50 0.1 0.01 1 0.1 0.01 10 LOAD CURRENT (A) 3.3V OUTPUT EFFICIENCY vs. LOAD CURRENT SMPS OUTPUT-VOLTAGE DEVIATION vs. LOAD CURRENT SWITCHING FREQUENCY vs.
PAGE 9
Dual Quick-PWM Step-Down Controller with LowPower LDO and RTC Regulator for MAIN Supplies STANDBY (ONLDO = RTC, ON1 = ON2 = GND) 0.01 SHUTDOWN (ONLDO = ON1 = ON2 = GND) 60 TA = +85°C TA = +25°C SAMPLE SIZE = 150 MAX17031 toc11 70 50 40 30 20 50 SAMPLE SIZE = 150 TA = +85°C TA = +25°C SAMPLE PERCENTAGE (%) SUPPLY CURRENT (mA) ICC + IDD SAMPLE PERCENTAGE (%) MAX17031 toc10 0.
PAGE 10
MAX17031 Dual Quick-PWM Step-Down Controller with LowPower LDO and RTC Regulator for MAIN Supplies Typical Operating Characteristics (continued) (Circuit of Figure 1, VIN = 12V, VDD = VCC = 5V, TA = +25°C, unless otherwise noted.) 5V SMPS LOAD TRANSIENT (1A TO 4A) POWER REMOVAL (SMPS UVLO RESPONSE) 3.3V SMPS LOAD TRANSIENT (1A TO 4A) MAX17031 toc19 MAX17031 toc21 MAX17031 toc20 12V 4A 4A A A 5V 0A A 0V 0A B 5V 3.3V B 5V B 0V C 0V D 0V 5V C 0A 40µs/div A. LOAD CURRENT, 2A/div C.
PAGE 11
Dual Quick-PWM Step-Down Controller with LowPower LDO and RTC Regulator for MAIN Supplies PIN NAME FUNCTION 9 PGOOD Open-Drain Power-Good Output for SMPS1 and SMPS2. PGOOD is low when either output voltage is more than 15% (typ) below the nominal regulation threshold, during soft-start, in shutdown, when either SMPS is disabled, and after the fault latch has been tripped. After the soft-start circuit has terminated, PGOOD becomes high impedance if both outputs are in regulation.
PAGE 12
MAX17031 Dual Quick-PWM Step-Down Controller with LowPower LDO and RTC Regulator for MAIN Supplies INPUT (VIN)* 7V TO 24V CIN 4x 10µF 25V CIN_PIN 0.1µF IN NH1 CBST1 0.1µF L1 5V OUTPUT DH1 DH2 BST1 BST2 LX1 LX2 NH2 CBST2 0.1µF L2 3.3V OUTPUT COUT2 COUT1 D1 DL1 NL1 DL2 D2 NL2 MAX17031 OUT1 DX1 OUT2 C5 10nF R6 100kΩ C6 0.1µF PGOOD DX2 12V TO 15V CHARGE PUMP C8 0.1µF C7 10nF COMBINED POWER-GOOD RTC RTC SUPPLY C3 1µF R4 1MΩ C4 0.
PAGE 13
Dual Quick-PWM Step-Down Controller with LowPower LDO and RTC Regulator for MAIN Supplies 400kHz/300kHz SMPS1: 5V AT 5A SMPS2: 3.3V AT 8A COMPONENT Input Voltage VIN = 7V to 24V Input Capacitor (CIN) 4X 10µF, 25V Taiyo Yuden TMK432BJ106KM SMPS 1 Output Capacitor (COUT1) 2x 100µF, 6V, 35m SANYO 6TPE100MAZB Inductor (L1) 4.3µH, 11.4m , 11A Sumida CEP125U High-Side MOSFET (NH1) Siliconix Si4800BDY 23m /30m 30V Low-Side MOSFET (NL1) Current-Limit Resistor (RILIM1) Table 2.
PAGE 14
MAX17031 Dual Quick-PWM Step-Down Controller with LowPower LDO and RTC Regulator for MAIN Supplies IN TON 5V LINEAR REGULATOR SKIP ONLDO LDO5 3.3V LINEAR REGULATOR RTC LDO BYPASS CIRCUITRY BYP ILIM2 OUT2 VDD SECFB ILIM1 OUT1 VDD BST1 PWM1 CONTROLLER (FIGURE 3) DH1 LX1 BST2 PWM2 CONTROLLER (FIGURE 3) DH2 LX2 VDD DL2 VDD DL1 ON1 UVLO PGOOD POWER-GOOD AND FAULT PROTECTION FAULT1 FB1 SELECT (PRESET 5V) FAULT2 FB2 SELECT (PRESET 3.
PAGE 15
Dual Quick-PWM Step-Down Controller with LowPower LDO and RTC Regulator for MAIN Supplies MAX17031 FB INT PRESET OR EXT ADJ REF INTEGRATOR ∆ FB ANALOG SOFT-START/ SOFT-STOP SLOPE COMP REFIN ON tOFF(MIN) AGND GND Q TRIG ONE-SHOT S Q DH DRIVER R* *RESET DOMINATE tON AGND Q TRIG ONE-SHOT NEG CURRENT LIMIT LX VCC ON-TIME COMPUTE VALLEY CURRENT LIMIT TON IN ILIM ULTRASONIC ZERO CROSSING Q TRIG ONE-SHOT GND ULTRASONIC THRESHOLD FB REFIN GND S Q SKIP THREE-LEVEL DECODE DL DRIVER R
PAGE 16
MAX17031 Dual Quick-PWM Step-Down Controller with LowPower LDO and RTC Regulator for MAIN Supplies The MAX17031 includes several features for multipurpose notebook functionality, and is specifically designed for 5V/3.3V main power-supply rails. The MAX17031 includes a 100mA, 5V linear regulator (LDO5) ideal for initial power-up of the notebook and main supply. Additionally, the MAX17031 includes a 3.
PAGE 17
Dual Quick-PWM Step-Down Controller with LowPower LDO and RTC Regulator for MAIN Supplies Forced-PWM Mode (VSKIP = 1.8V) The low-noise forced-PWM mode (VSKIP = 1.8V) disables the zero-crossing comparator, which controls the low-side switch on-time. This forces the low-side gatedrive waveform to constantly be the complement of the high-side gate-drive waveform, so the inductor current reverses at light loads while DH maintains a duty factor of VOUT/VIN.
PAGE 18
MAX17031 Dual Quick-PWM Step-Down Controller with LowPower LDO and RTC Regulator for MAIN Supplies Secondary Feedback (SKIP) When the controller skips pulses (VSKIP > 2V), the long time between pulses (especially if the output is sinking current) allows the external charge-pump voltage or transformer secondary winding voltage to drop. Connecting a resistor-divider between the secondary output to SKIP to ground sets up a minimum refresh threshold.
PAGE 19
Dual Quick-PWM Step-Down Controller with LowPower LDO and RTC Regulator for MAIN Supplies PGOOD is the open-drain output that continuously monitors both output voltages for undervoltage and overvoltage conditions. PGOOD is actively held low in shutdown (ON1 or ON2 = GND), during soft-start, and soft-shutdown. Approximately 20µs (typ) after the softstart terminates, PGOOD becomes high impedance as long as both output voltages exceed 85% of the nominal fixed-regulation voltage.
PAGE 20
Dual Quick-PWM Step-Down Controller with LowPower LDO and RTC Regulator for MAIN Supplies MAX17031 Inductor Operating Point: This choice provides trade-offs between size vs. efficiency and transient response vs. output ripple. Low inductor values provide better transient response and smaller physical size, but also result in lower efficiency and higher output ripple due to increased ripple currents.
PAGE 21
Dual Quick-PWM Step-Down Controller with LowPower LDO and RTC Regulator for MAIN Supplies VSTEP ∆ILOAD(MAX) In applications without large and fast load transients, the output capacitor’s size often depends on how much ESR is needed to maintain an acceptable level of output voltage ripple. The output ripple voltage of a stepdown controller equals the total inductor ripple current multiplied by the output capacitor’s ESR.
PAGE 22
MAX17031 Dual Quick-PWM Step-Down Controller with LowPower LDO and RTC Regulator for MAIN Supplies Power-MOSFET Selection Most of the following MOSFET guidelines focus on the challenge of obtaining high load-current capability when using high-voltage (> 20V) AC adapters. Lowcurrent applications usually require less attention. The high-side MOSFET (NH) must be able to dissipate the resistive losses plus the switching losses at both VIN(MIN) and VIN(MAX).
PAGE 23
Dual Quick-PWM Step-Down Controller with LowPower LDO and RTC Regulator for MAIN Supplies Step-Down Converter Dropout Performance The output voltage-adjustable range for continuousconduction operation is restricted by the nonadjustable minimum off-time one-shot. When working with low input voltages, the duty-factor limit must be calculated using worst-case values for on- and off-times. Manufacturing tolerances and internal propagation delays introduce an error to the TON K-factor.
PAGE 24
MAX17031 Dual Quick-PWM Step-Down Controller with LowPower LDO and RTC Regulator for MAIN Supplies Layout Procedure 1) Place the power components first, with ground terminals adjacent (NL_ source, CIN, COUT_, and DL_ anode). If possible, make all these connections on the top layer with wide, copper-filled areas. 2) Mount the controller IC adjacent to the low-side MOSFET, preferably on the back side opposite NL_ and NH_ in order to keep LX_, GND, DH_, and the DL_ gate-drive lines short and wide.