Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsPMICsPMIC - linear/switching voltage regulator Arbitrary function SSOP 28

__________________General Description

The MAX786 is a system-engineered power-supply

controller for notebook computers or similar battery-

powered equipment. It provides two high-performance

step-down (buck) pulse-width modulators (PWMs)

for +3.3V and +5V. Other features include dual,

low-dropout, micropower linear regulators for

CMOS/RTC back-up, and two precision low-battery-

detection comparators.

High efficiency (95% at 2A; greater than 80% at loads

from 5mA to 3A) is achieved through synchronous recti-

fication and PWM operation at heavy loads, and

Idle Mode

operation at light loads. The MAX786 uses

physically small components, thanks to high operating

frequencies (300kHz/200kHz) and a new current-mode

PWM architecture that allows for output filter capacitors

as small as 30µF per ampere of load. Line- and load-

transient responses are terrific, with a high 60kHz unity-

gain crossover frequency allowing output transients to

be corrected within four or five clock cycles. Low sys-

tem cost is achieved through a high level of integration

and the use of low-cost, external N-channel MOSFETs.

Other features include low-noise, fixed-frequency PWM

operation at moderate to heavy loads, and a synchro-

nizable oscillator for noise-sensitive applications such

as electromagnetic pen-based systems and communi-

cating computers. The MAX786 is a monolithic,

BiCMOS IC available in fine-pitch, surface-mount

SSOP packages.

___________________________Applications

Notebook Computers

Portable Data Terminals

Communicating Computers

Pen-Entry Systems

________________________________Features

♦ Dual PWM Buck Controllers (+3.3V and +5V)

♦ Two Precision Comparators or Level Translators

♦ 95% Efficiency

♦ 420µA Quiescent Current, 70µA in Standby

(linear regulators alive)

♦ 25µA Shutdown Current (+5V linear alive)

♦ 5.5V to 30V Input Range

♦ Small SSOP Package

♦ Fixed Output Voltages:

3.3V (standard)

3.45V (High-Speed Pentium

™)

3.6V (PowerPC™)

_________________Ordering Information

MAX786

Dual-Output Power-Supply

Controller for Notebook Computers

_______________________________________________________________________

Maxim Integrated Products

19-0160; Rev 2; 4/97

_____________________Pin Configuration

FB3

DH3

LX3

BST3

ON3

SS3

CS3

TOP VIEW

DL3

V+

FB5

PGND

DL5

BST5

LX5

SHDN

SYNC

REF

GND

SSOP

MAX786

DH5

CS5

SS5

ON5

Idle Mode is a trademark of Maxim Integrated Products. Pentium is a trademark of Intel Corp. PowerPC is a trademark of IBM Corp.

________Typical Application Diagram

MAX786

5.5V

30V

SHUTDOWN

POWER

SECTION

POWER-GOOD

LOW-BATTERY WARNING

µP

MEMORY

PERIPHERALS

+3.3V

+5V

5V ON/OFF

3.3V ON/OFF

SYNC

SUSPEND POWER

28 SSOP0°C to +70°CMAX786RCAI

28 SSOP0°C to +70°CMAX786CAI

PIN-PACKAGETEMP. RANGEPART

3.45V

3.3V

OUT

Ordering Information continued at end of data sheet.

EVALUATION KIT

INFORMATION INCLUDED

For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.

For small orders, phone 1-800-835-8769.

Summary of content (20 pages)

PAGE 1
9-0160; Rev 2; 4/97 KIT ATION EVALU LUDED C IN TION A M R O INF Dual-Output Power-Supply Controller for Notebook Computers ________________________________Features The MAX786 is a system-engineered power-supply controller for notebook computers or similar batterypowered equipment. It provides two high-performance step-down (buck) pulse-width modulators (PWMs) for +3.3V and +5V.
PAGE 2
MAX786 Dual-Output Power-Supply Controller for Notebook Computers ABSOLUTE MAXIMUM RATINGS V+ to GND................................................................-0.3V to 36V PGND to GND .......................................................................±2V VL to GND ..................................................................-0.3V to 7V BST3, BST5 to GND .................................................-0.3V to 36V LX3 to BST3 ...............................................................
PAGE 3
Dual-Output Power-Supply Controller for Notebook Computers (V+ = 15V, GND = PGND = 0V, IVL = IREF = 0mA, SHDN = ON3 = ON5 = 5V, other digital input levels are 0V or +5V, TA = TMIN to TMAX, unless otherwise noted.) PARAMETER CONDITIONS MIN TYP MAX UNITS 12 20 30 µA VH = 15V, VOUT = 2.5V 200 500 1000 µA ISOURCE = 5µA, VH = 3V VH - 0 .5 Q1, Q2 Source Current VH = 15V, VOUT = 2.
PAGE 4
________________________________________________Typical Operating Characteristics (Circuit of Figure 1, TA = +25°C, unless otherwise noted.) EFFICIENCY vs. +5V OUTPUT CURRENT, 200kHz EFFICIENCY vs. +5V OUTPUT CURRENT, 300kHz VIN = 30V 80 70 80 VIN = 30V 70 +3.3V OFF SYNC = 0V, +3.
PAGE 5
Dual-Output Power-Supply Controller for Notebook Computers PULSE-WIDTH MODULATION MODE WAVEFORMS IDLE MODE WAVEFORMS +5V OUTPUT 50mV/div LX 10V/div 2V/div +5V OUTPUT 50mV/div 500ns/div +5V OUTPUT CURRENT = 1A VIN= 16V 200µs/div ILOAD = 100mA VIN = 10V +5V LOAD-TRANSIENT RESPONSE +3.3V LOAD-TRANSIENT RESPONSE 3A 0A 3A LOAD CURRENT 0A +5V OUTPUT 50mV/div 200µs/div VIN = 15V LOAD CURRENT +3.
PAGE 6
MAX786 Dual-Output Power-Supply Controller for Notebook Computers _________________________________Typical Operating Characteristics (continued) (Circuit of Figure 1, TA = +25°C, unless otherwise noted.) +5V LINE-TRANSIENT RESPONSE, FALLING +5V LINE-TRANSIENT RESPONSE, RISING +5V OUTPUT 50mV/div +5V OUTPUT 50mV/div VIN, 10V TO 16V 2V/div VIN, 16V TO 10V 2V/div 20µs/div ILOAD = 2A 20µs/div ILOAD = 2A +3.3V LINE-TRANSIENT RESPONSE, RISING +3.3V LINE-TRANSIENT RESPONSE, FALLING +3.
PAGE 7
Dual-Output Power-Supply Controller for Notebook Computers PIN NAME 1 CS3 Current-sense input for +3.3V; +100mV = current limit level referenced to FB3. FUNCTION 2 SS3 Soft-start input for +3.3V. Ramp time to full current limit is 1ms/nF of capacitance to GND. 3 ON3 ON/OFF control input disables the +3.3V PWM. Tie directly to VL for automatic start-up. 4 D1 #1 level-translator/comparator noninverting input, threshold = +1.650V. Controls Q1. Tie to GND if unused.
PAGE 8
MAX786 Dual-Output Power-Supply Controller for Notebook Computers _________________Detailed Description The MAX786 has two close relatives: the MAX782 and the MAX783. The MAX782 and MAX783 each include an extra flyback winding regulator and linear regulators for dual, +12V/programmable PCMCIA VPP outputs. The MAX782/MAX783 data sheet contains extra applications information on the MAX786 not found in this data sheet. The MAX786 converts a 5.5V to 30V input to four outputs (Figure 1).
PAGE 9
Dual-Output Power-Supply Controller for Notebook Computers +5V LDO LINEAR REGULATOR V+ VL Programmable soft-start is set by an optional external capacitor; this reduces in-rush surge currents upon start-up and provides adjustable power-up times for power-supply sequencing purposes. P FB3 3.3V PWM CONTROLLER (SEE FIG. 3) 5V 3.3V 4.5V +3.3V REFERENCE ON REF CS3 BST3 DH3 LX3 DL3 ON SS3 SHDN PGND GND 4V FAULT ON3 FB5 CS5 2.
PAGE 10
MAX786 Dual-Output Power-Supply Controller for Notebook Computers +5V Switch-Mode Supply The +5V output is produced by a current-mode, PWM step-down regulator, which is nearly identical to the +3.3V supply. The +5V supply’s dropout voltage, as configured in Figure 1, is typically 400mV at 2A. As V+ approaches 5V, the +5V output gracefully falls with V+ until the VL regulator output hits its undervoltagelockout threshold at 4V. At this point, the +5V supply turns off.
PAGE 11
Dual-Output Power-Supply Controller for Notebook Computers Ringing seen at the high-side MOSFET gates (DH3 and DH5) in discontinuous-conduction mode (light loads) is a natural operating condition caused by the residual energy in the tank circuit formed by the inductor and stray capacitance at the LX_ nodes. The gate driver negative rail is referred to LX_, so any ringing there is directly coupled to the gate-drive supply. CS_ 1X 60kHz LPF FB_ MAIN PWM COMPARATOR REF, 3.
PAGE 12
MAX786 Dual-Output Power-Supply Controller for Notebook Computers Modes of Operation PWM Mode Under heavy loads—over approximately 25% of full load — the +3.3V and +5V supplies operate as continuouscurrent PWM supplies (see Typical Operating Characteristics).
PAGE 13
Dual-Output Power-Supply Controller for Notebook Computers MAX786 Table 1. Surface-Mount Components (See Figure 1 for Standard Application Circuit.) COMPONENT 33µF, 35V tantalum capacitors AVX Sprague PART NO. TPSE226M035R0100 595D336X0035R C2 4.7µF, 6V tantalum capacitor AVX Sprague TAJB475M016 595D475X0016A C3 1µF, 20V tantalum capacitor AVX Sprague TAJA105M025 595D105X0020A2B C4, C5 0.
PAGE 14
MAX786 Dual-Output Power-Supply Controller for Notebook Computers VIN(MAX), the maximum input (battery) voltage. This value should include the worst-case conditions under which the power supply is expected to function, such as no-load (standby) operation when a battery charger is connected but no battery is installed. VIN(MAX) cannot exceed 30V. VIN(MIN), the minimum input (battery) voltage. This value should be taken at the full-load operating current under the lowest battery conditions.
PAGE 15
Dual-Output Power-Supply Controller for Notebook Computers In idle-mode, the ripple has a capacitive and resistive component: (4) (10-4) (L) VOUT(RPL)(C) = ——————— x (RCS2) (CF) 1 1 ——— + ————— Volts VOUT VIN - VOUT ( ) (0.02) (ESRCF) VOUT(RPL)(R) = ———————Volts RCS The total ripple, VOUT(RPL), can be approximated as follows: if VOUT(RPL)(R) < 0.5 VOUT(RPL)(C), then VOUT(RPL) = VOUT(RPL)(C), otherwise, VOUT(RPL) = 0.5 VOUT(RPL)(C) + VOUT(RPL)(R). Diodes D1 and D3 Use 1N5819s or similar Schottky diodes.
PAGE 16
MAX786 Dual-Output Power-Supply Controller for Notebook Computers Other ways to shut down the MAX786 are suggested in the applications section of the MAX782/MAX783 data sheet. Table 3. EV Kit Power-Supply Controls (SW1) ON OFF SETTING SETTING SWITCH NAME FUNCTION 1 SHDN Enable shutdown mode Operate Shutdown 2 ON3 Enable 3.3V power supply 3.3V ON 3.3V OFF 3 ON5 Enable 5.
PAGE 17
Dual-Output Power-Supply Controller for Notebook Computers The MAX786 evaluation kit (EV kit) embodies the standard application circuit, with some extra pullup and pull-down resistors needed to set default logic signal levels. The board comes configured to accept battery input voltages between 6.5V and 30V, and provides up to 25W of output power. All functions are con- 1.0" trolled by standard CMOS/TTL logic levels or DIP switches.
PAGE 18
MAX786 Dual-Output Power-Supply Controller for Notebook Computers 1.0" Figure 10. MAX786 EV Kit, Bottom Component Layout and Silk Screen, Bottom View 1.0" Figure 11.
PAGE 19
Dual-Output Power-Supply Controller for Notebook Computers MAX786 ______________________Chip Topography SS3 CS3 FB3 DH3 ON3 D1 D2 LX3 BST3 DL3 VH Q2 Q1 V+ 0.181" VL (4.597mm) FB5 PGND GND DL5 REF BST5 SYNC LX5 SHDN ON5 SS5 CS5 DH5 0.109" (2.
PAGE 20
__Ordering Information (continued) PART TEMP. RANGE PIN-PACKAGE VOUT MAX786SCAI 0°C to +70°C 28 SSOP MAX786C/D 0°C to +70°C Dice* MAX786EAI -40°C to +85°C 28 SSOP 3.3V MAX786REAI -40°C to +85°C 28 SSOP 3.45V MAX786SEAI -40°C to +85°C 28 SSOP 3.6V 3.6V — EV KIT TEMP. RANGE BOARD TYPE MAX786EVKIT-SO 0°C to +70°C Surface Mount *Contact factory for dice specifications. ________________________________________________________Package Information SSOP.