Datasheet

ManualsBrandsLINEAR TECHNOLOGY ManualsPMICsPMIC - OR controller, electrical elements n-channel SSOP 16 Source selector

LTC1473

Dual PowerPath

Switch Driver

■

Power Path Management for Systems with Multiple

DC Sources

■

All N-Channel Switching to Reduce Power Losses and

System Cost

■

Switches and Isolates Sources Up to 30V

■

Adaptive High Voltage Step-Up Regulator for N-Channel

Gate Drive

■

Capacitor Inrush and Short-Circuit Current Limited

■

User-Programmable Timer to Limit Switch Dissipation

■

Small Footprint: 16-Pin Narrow SSOP

The LTC

1473 provides a power management solution for

single and dual battery notebook computers and other

portable equipment. The LTC1473 drives two sets of back-

to-back N-channel MOSFET switches to route power to the

input of the main system switching regulator. An internal

boost regulator provides the voltage to fully enhance the

logic level N-channel MOSFET switches.

The LTC1473 senses current to limit surge currents both

into and out of the batteries and the system supply

capacitor during switch-over transitions or during fault

conditions. A user-programmable timer monitors the time

the MOSFET switches are in current limit and latches them

off when the programmed time is exceeded.

A unique “2-diode mode” logic ensures system start-up

regardless of which input receives power first.

■

Notebook Computers

■

Portable Instruments

■

Handi-Terminals

■

Portable Medical Equipment

■

Portable Industrial Control Equipment

PowerPath is a trademark of Linear Technology Corporation.

, LTC and LT are registered trademarks of Linear Technology Corporation.

IN1

IN2

DIODE

TIMER

GND

GA1

SAB1

GB1

SENSE

–

GA2

SAB2

GB2

LTC1473

OUT

SENSE

0.04Ω

1µF

MMBD914LTI

1mH*

Si9926DY

MMBD2838LTI

1473 TA01

BAT1

DCIN

BAT2

INPUT OF SYSTEM

HIGH EFFICIENCY DC/DC

SWITCHING REGULATOR

(LTC1735, ETC)

FROM POWER

MANAGEMENT

µP

TIMER

4700pF

MBRD340

Si9926DY

*COILCRAFT 1812LS-105XKBC

FEATURES

DESCRIPTIO

APPLICATIO S

TYPICAL APPLICATION

Summary of content (16 pages)

PAGE 1
LTC1473 Dual PowerPathTM Switch Driver U FEATURES ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO Power Path Management for Systems with Multiple DC Sources All N-Channel Switching to Reduce Power Losses and System Cost Switches and Isolates Sources Up to 30V Adaptive High Voltage Step-Up Regulator for N-Channel Gate Drive Capacitor Inrush and Short-Circuit Current Limited User-Programmable Timer to Limit Switch Dissipation Small Footprint: 16-Pin Narrow SSOP U APPLICATIO S ■ ■ ■ ■ Notebook Computers Portable Instruments
PAGE 2
LTC1473 W U PACKAGE/ORDER INFORMATION U W W W (Note 1) DCIN, BAT1, BAT2 Supply Voltage .............. – 0.3 to 32V SENSE +, SENSE –, V + .................................. – 0.3 to 32V GA1, GB1, GA2, GB2 ................................... – 0.3 to 42V SAB1, SAB2 ................................................. – 0.3 to 32V SW, VGG ...................................................... – 0.3 to 42V IN1, IN2, DIODE ........................................– 0.3V to 7.
PAGE 3
LTC1473 ELECTRICAL CHARACTERISTICS Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: TJ is calculated from the ambient temperature TA and power dissipation PD according to the following formula: TJ = TA + (PD)(150°C/W) Note 3: IS increases by the same amount as IBSENSE + + IBSENSE – when their common mode falls below 5V. Note 4: Gate turn-on and turn-off times are measured with no inrush current limiting, i.e., VSENSE = 0V.
PAGE 4
LTC1473 U W TYPICAL PERFORMANCE CHARACTERISTICS 2.0 1.8 45 V + = 20V CLOAD = 1000pF VSAB = 20V GATE FALL TIME 1.6 1.4 TURN-OFF DELAY 1.2 1.0 0.8 0.6 0.4 – 50 – 25 25 50 75 0 TEMPERATURE (°C) 100 40 35 V + = 20V CLOAD = 1000pF VSAB = 0V 40 TURN-ON DELAY 25 20 15 10 1.7 1.6 VHIGH 1.4 1.3 VLOW 1.1 1.0 – 50 – 25 25 50 75 0 TEMPERATURE (°C) 100 25 50 75 0 TEMPERATURE (°C) 100 125 1.28 VHIGH 1.7 1.6 1.5 VLOW 1.4 1.3 1.2 1.1 1.0 – 50 – 25 25 50 75 0 TEMPERATURE (°C) 100 1.24 1.
PAGE 5
LTC1473 U U U PIN FUNCTIONS IN1 (Pin 1): Logic Input of Gate Drivers GA1 and GB1. IN1 is disabled when IN2 is high or DIODE is low. IN2 (Pin 2): Logic Input of Gate Drivers GA2 and GB2. IN2 is disabled when IN1 is high or DIODE is low. DIODE (Pin 3): “2-Diode Mode” Logic Input. DIODE overrides IN1 and IN2 by forcing the two back-to-back external N-channel MOSFET switches to mimic two diodes. TIMER (Pin 4): Fault Timer.
PAGE 6
LTC1473 W FUNCTIONAL DIAGRA U U 16 GA1 SW A1/B1 GATE DRIVERS IN1 1 IN2 2 DIODE 15 SAB1 14 GB1 13 SENSE + INRUSH CURRENT SENSE 12 SENSE – 3 11 GA2 V+ SW A2/B2 GATE DRIVERS 5.5µA 10 SAB2 9 GB2 TIMER 4 TO GATE DRIVERS V+ 5 VGG 6 SW 7 R 900k VGG SWITCHING REGULATOR GND LATCH + S – 1.
PAGE 7
LTC1473 U OPERATION The LTC1473 is responsible for low-loss switching and isolation at the “front end” of the power management system, where up to two battery packs can be connected and disconnected seamlessly. Smooth switching between input power sources is accomplished with the help of lowloss N-channel switches. They are driven by special gate drive circuitry which limits the inrush current in and out of the battery packs and the system power supply capacitors.
PAGE 8
LTC1473 U W U U APPLICATIONS INFORMATION After the transition period, the VGS of both MOSFETs in the selected switch pair rises to approximately 5.6V. The gate drive is set at 5.6V to provide ample overdrive for standard logic-level MOSFET switches without exceeding their maximum VGS rating. In the event of a fault condition the current limit loop will limit the inrush current into the short. At the instant the MOSFET switch is in current limit, i.e.
PAGE 9
LTC1473 U W U U APPLICATIONS INFORMATION The back-to-back topology also allows for independent control of each half of the switch pair which facilitates bidirectional inrush current limiting and the so-called “2-diode mode” described in the following section. management µP is powered even under start-up or abnormal operating conditions. (An undervoltage lockout circuit defeats this mode when the V + pin drops below approximately 3.2V.
PAGE 10
LTC1473 U W U U APPLICATIONS INFORMATION As a general rule, select the switch with the lowest RDS(ON) and able to withstand the maximum allowable VDS. This will minimize the heat dissipated in the switches while increasing the overall system efficiency. Higher switch resistances can be tolerated in some systems with lower current requirements, but care should be taken to ensure that the power dissipated in the switches is never allowed to rise above the manufacturers’ recommended level.
PAGE 11
LTC1473 U W U U APPLICATIONS INFORMATION VGG Regulator Inductor and Capacitors The VGG regulator provides a power supply voltage 8.5V higher than any of the three main power source voltages to allow the control of N-channel MOSFET switches. This micropower, step-up voltage regulator is powered by the highest potential available from the three main power sources for maximum regulator efficiency. Three external components are required by the VGG regulator: L1, C1 and C2, as shown in Figure 5.
PAGE 12
LTC1473 U TYPICAL APPLICATIONS Input Power Routing Circuit for Microprocessor Controlled Dual Battery Dual Chemistry System Si9926DY Si9926DY 16 15 14 RSENSE 0.
PAGE 13
LTC1473 U TYPICAL APPLICATIONS Complete Front End Including Battery Charger and DC/DC Converter with Automatic Switchover Between Battery and DCIN C2, 0.1µF COSC 57pF 1 CSS, 0.1µF RC, 10k TG RUN/SS 3 CC2, 51pF C1 100pF COSC 2 BOOST ITH SW 16 15 14 13 LTC1735 12 INTVCC SGND 11 6 BG VOSENSE 10 7 – SENSE PGND 9 8 SENSE + EXTVCC VOUT 4 CC 330pF SFB C4 0.1µF D1 CMDSH-3 VIN L1* 10µH 5 C5 1000pF CIN 22µF 35V ×2 + Q1 Si4412DY + C3 4.7µF 16V Q2 Si4412DY RSENSE 0.
PAGE 14
LTC1473 U TYPICAL APPLICATION Protected Automatic Switchover Between Two Supplies 1 5V LT1121-5 8 Q1 Si9926DY 3 SUPPLY V1 10k 1µF 1M D1 MMBD2838LT1 1M 3 + 8 LT1490 1 2 – 1 5 4 1M 10k 3 7 6 1M 2 + 4 – 5 C6 4700pF 6 + C7 1µF L1*, 1mH + C5 1µF 7 8 LTC1473 IN1 GA1 IN2 SAB1 16 15 14 DIODE GB1 TIMER SENSE + V+ 12 SENSE – VGG GA2 SW SAB2 GND GB2 R3 0.
PAGE 15
LTC1473 U PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. GN Package 16-Lead Plastic SSOP (Narrow 0.150) (LTC DWG # 05-08-1641) 0.189 – 0.196* (4.801 – 4.978) 16 15 14 13 12 11 10 9 0.229 – 0.244 (5.817 – 6.198) 0.150 – 0.157** (3.810 – 3.988) 1 0.015 ± 0.004 × 45° (0.38 ± 0.10) 0.007 – 0.0098 (0.178 – 0.249) 0.009 (0.229) REF 2 3 4 5 6 7 0.053 – 0.068 (1.351 – 1.727) 8 0.004 – 0.0098 (0.102 – 0.249) 0° – 8° TYP 0.016 – 0.050 (0.406 – 1.270) 0.008 – 0.012 (0.
PAGE 16
LTC1473 U TYPICAL APPLICATIONS Protected Hot SwapTM Switchover Between Two Supplies DOCKING CONNECTOR OTHER 5V LOGIC SUPPLY 5V LONG PIN 100k Q1 Si4936DY SUPPLY V1 5V D1 MMBD2838LT1 1 2 3 4 100k 5 C6 4700pF 6 L1*, 1mH C7 1µF C5 1µF 7 8 LTC1473 IN1 GA1 IN2 SAB1 16 15 14 DIODE GB1 TIMER 13 SENSE + V+ SENSE – VGG GA2 SW SAB2 GND GB2 SUPPLY V2 12V R3 0.