Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsPMICsPMIC - system monitor Serialiser TQFN 36

General Description

The MAX6876 EEPROM-configurable, multivoltage

power tracker/supervisor monitors four system voltages

and ensures proper power-up and power-down condi-

tions for systems requiring voltage tracking and/or

sequencing. The MAX6876 provides a highly config-

urable solution as key thresholds and timing parame-

ters are programmed through an I

C interface and

these values are stored in internal EEPROM. The

MAX6876 also provides supervisory functions and an

overcurrent detection circuit.

The MAX6876 features programmable undervoltage and

overvoltage thresholds for each input supply. When all

voltages are within specifications, the device turns on the

external n-channel MOSFETs to either sequence or track

the voltages to the system. All of the voltages can be

sequenced or tracked or powered up with a combination

of the two options. During tracking, the voltage at the

GATE of each MOSFET is increased to slowly turn on

each supply. The voltages at the source of each MOSFET

are compared to each other to ensure that the voltage dif-

ferential between each monitored supply does not

exceed 250mV (typ). Tracking is dynamically adjusted to

force all outputs to track within a ±125mV window from a

reference ramp; if, for any reason, any supply fails to

track within ±250mV from the reference ramp, a FAULT

output is asserted, the power-up mode is terminated, and

all outputs are powered off. Power-up mode is also termi-

nated if the controlled voltages fail to complete the ramp-

up within a programmable FAULT timeout. The MAX6876

features latch-off and autoretry modes to power on again

after a fault condition has been detected.

Other features of the MAX6876 include a reset circuit, a

manual reset input (MR), and a margin disable input

(MARGIN). The device also features outputs for indicat-

ing a power-good condition (PG_) and an overcurrent

condition (OC), and a bus-removal (REM) output.

The MAX6876 is available in a small 6mm x 6mm, 36-

pin thin QFN package and is fully specified over the

extended -40°C to +85°C temperature range.

Applications

Features

♦ Tracking/Sequencing for Up to Four Supply

Voltages (With One MAX6876 Device) and

Tracking for Up to 16 Supply Voltages (Using

Four MAX6876 Devices)

♦ EEPROM-Configurable Tracking/Sequencing

Control

♦ Bus Voltage Independent Operation (MAX6876 Is

Powered from the Tracked Supply Voltages or

Always-On Supply)

♦ EEPROM-Selectable Undervoltage/Overvoltage-

Lockout Thresholds for Each Input Supply

♦ EEPROM-Selectable Power-Up/Down Slew Rate

♦ Programmable Power-Good Output Thresholds

and Timing

♦ Global Adjustable Undervoltage Lockout or Logic

ENABLE Input

♦ Independent Internal Charge Pumps to Enhance

External n-Channel FETs (V

GATE_SOURCE

= 5V)

♦ Post Power-Up Selectable Overcurrent Detection

♦ 0.5V to 5.5V IN_ Threshold Range

♦ ±1.5% Threshold Accuracy

♦ I

C/SMBus™-Compatible Serial Interface

♦ Small 6mm x 6mm, 36-Pin Thin QFN Package

MAX6876

EEPROM-Programmable, Quad,

Power-Supply Tracker/Sequencer Circuit

________________________________________________________________ Maxim Integrated Products 1

IN4

GATE4

REFIN

N.C.

PG2

PG1

PG4

PG3

OUT4

ABP

TRKEN

SYNCH

REM

FAULT

SDA

SCL

N.C.

MARGIN

ENABLE

RESET

GATE1

OUT1

IN2

GATE2

OUT2

IN3

GATE3

OUT3

IN1

6mm x 6mm

THIN QFN

MAX6876

TOP VIEW

HOLD

GND

36 35 34 33 32 31 30 29 28

10 11 12 13 14 15 16 17 18

EP*

*EXPOSED PADDLE

Pin Configuration

Ordering Information

19-3479; Rev 0; 10/04

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at

1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

EVALUATION KIT

AVAILABLE

PART

TEMP RANGE

PIN-

PACKAGE

PKG

CODE

MAX6876ETX

-40°C to +85°C 36 Thin QFN T3666-3

Multivoltage Systems

Networking Systems

Telecom

Storage Equipment

Servers/Workstations

SMBus is a trademark of Intel Corp.

Summary of content (39 pages)

PAGE 1
9-3479; Rev 0; 10/04 KIT ATION EVALU E L B AVAILA EEPROM-Programmable, Quad, Power-Supply Tracker/Sequencer Circuit Applications Multivoltage Systems Networking Systems Telecom Storage Equipment Servers/Workstations ♦ EEPROM-Configurable Tracking/Sequencing Control ♦ Bus Voltage Independent Operation (MAX6876 Is Powered from the Tracked Supply Voltages or Always-On Supply) ♦ EEPROM-Selectable Undervoltage/OvervoltageLockout Thresholds for Each Input Supply ♦ EEPROM-Selectable Power-Up/Down Slew Rate ♦
PAGE 2
MAX6876 EEPROM-Programmable, Quad, Power-Supply Tracker/Sequencer Circuit ABSOLUTE MAXIMUM RATINGS (All voltages are referenced to GND, unless otherwise noted.) GATE_.............................................................-0.3V to (IN_ + 6V) IN1–IN4, VCC ............................................................-0.3V to +6V OUT1–OUT4, SYNCH, ABP, REFIN...............................-0.3V to Max (IN1–IN4, VCC ) + 0.3V ENABLE, TRKEN, HOLD, FAULT, MR, MARGIN......-0.3V to +6V RESET, PG1–PG4, OC, REM...
PAGE 3
EEPROM-Programmable, Quad, Power-Supply Tracker/Sequencer Circuit (VCC, IN1–IN4 = +2.7V to +5.5V; ENABLE = MARGIN = MR = ABP = TRKEN; TA = -40°C to +85°C, unless otherwise specified. Typical values are at TA = +25°C.
PAGE 4
MAX6876 EEPROM-Programmable, Quad, Power-Supply Tracker/Sequencer Circuit ELECTRICAL CHARACTERISTICS (continued) (VCC, IN1–IN4 = +2.7V to +5.5V; ENABLE = MARGIN = MR = ABP = TRKEN; TA = -40°C to +85°C, unless otherwise specified. Typical values are at TA = +25°C.
PAGE 5
EEPROM-Programmable, Quad, Power-Supply Tracker/Sequencer Circuit (VCC, IN1–IN4 = +2.7V to +5.5V; ENABLE = MARGIN = MR = ABP = TRKEN; TA = -40°C to +85°C, unless otherwise specified. Typical values are at TA = +25°C.) (Note 1) PARAMETER TRKEN Input Delay SYMBOL tEN TRKEN Reference Voltage Range VTRKEN TRKEN Input Current ITRKEN Reference Input Voltage Range VREFIN Reference Input Resistance RREFIN CONDITIONS MIN TRKEN falling, 100mV overdrive TYP MAX 2 UNITS µs Input rising 1.245 1.
PAGE 6
MAX6876 EEPROM-Programmable, Quad, Power-Supply Tracker/Sequencer Circuit ELECTRICAL CHARACTERISTICS (continued) (VCC, IN1–IN4 = +2.7V to +5.5V; ENABLE = MARGIN = MR = ABP = TRKEN; TA = -40°C to +85°C, unless otherwise specified. Typical values are at TA = +25°C.) (Note 1) Note 5: The MAX6876 programmed as a single device; GATE timeout has counted prior to beginning each sequence of power-up. GATE timeout is not enabled during power-down or when the device is programmed as a master/slave.
PAGE 7
EEPROM-Programmable, Quad, Power-Supply Tracker/Sequencer Circuit VTRKEN BUS VOLTAGE MONITORED THROUGH TRKEN INPUT VTRKEN GND IN1 = 3.3V IN2 = 2.5V IN3 = 1.8V IN4 = 1.5V MONITORED THROUGH SET THRESHOLDS ON IN_ INPUTS (EEPROM-SELECTABLE) EEPROMADJUSTED SLEW RATE OUT1 = 3.3V GND OUT2 = 2.5V OUT3 = 1.8V tGATE tGATE tGATE tGATE OUT4 = 1.5V GND tRESET GND RESET Figure 2.
PAGE 8
EEPROM-Programmable, Quad, Power-Supply Tracker/Sequencer Circuit MAX6876 Timing Diagrams (continued) VTRKEN VTRKEN BUS VOLTAGE MONITORED THROUGH TRKEN INPUT GND IN1 = 2.5V IN2 = 1.8V IN3 = 0.9V IN4 = 0.7V MONITORED THROUGH SET THRESHOLDS ON IN_ INPUTS (EEPROM-SELECTABLE) GND EEPROMSELECTED SLEW RATE OUT1 = 2.5V EEPROMSELECTED SLEW RATE (FORCED INTO QUICK SHUTDOWN WHEN IN1 FAILS) OUT2 = 1.8V OUT3 = 0.9V OUT4 = 0.7V GND GATE tRESET GND RESET Figure 3.
PAGE 9
EEPROM-Programmable, Quad, Power-Supply Tracker/Sequencer Circuit (VCC = 3.3V, ENABLE = MARGIN = MR = ABP = TRKEN, TA = +25°C, unless otherwise noted.) NORMALIZED TIMEOUT PERIOD vs. TEMPERATURE 1.70 1.60 1.50 1.40 1.30 1.20 1.10 1.015 1.010 1.005 1.050 NORMALIZED IN_ 1.000 0.995 0.990 0.985 0.950 0.980 1.00 0.90 0.975 0.900 2.7 3.4 4.1 4.8 -40 5.5 -15 10 35 60 85 -40 -15 10 35 60 85 SUPPLY VOLTAGE (V) TEMPERATURE (°C) TEMPERATURE (°C) MAXIMUM IN_ TRANSIENT DURATION vs.
PAGE 10
MAX6876 EEPROM-Programmable, Quad, Power-Supply Tracker/Sequencer Circuit Typical Operating Characteristics (continued) (VCC = 3.3V, ENABLE = MARGIN = MR = ABP = TRKEN, TA = +25°C, unless otherwise noted.) MIXED MODE MIXED MODE WITH FAST SHUTDOWN MAX6876 toc10 MAX6876 toc11 OUT4 OUT4 OUT3 OUT2 OUT3 OUT_ 1V/div OUT2 OUT1 OUT_ 1V/div OUT1 0V 0V 20ms/div 20ms/div Pin Description PIN NAME FUNCTION 1 VCC Optional Supply Voltage Input. Connect VCC to an alternate (i.e.
PAGE 11
EEPROM-Programmable, Quad, Power-Supply Tracker/Sequencer Circuit PIN NAME FUNCTION OC Active-Low, Open-Drain Overcurrent Output. OC asserts low if any monitored IN_ to OUT_ voltage falls out of the selected percentage of the IN_ voltage range (VTH_OC) for more than the programmed tOC. OC monitoring begins only after supply tracking or sequencing has been completed and is disabled during power-down operation. 8 REM Open-Drain Bus Removal Output.
PAGE 12
EEPROM-Programmable, Quad, Power-Supply Tracker/Sequencer Circuit MAX6876 Pin Description (continued) PIN 24 REFIN 25 OUT4 26 GATE4 27 28 29 30 31 12 NAME IN4 FUNCTION Reference Voltage Input. The MAX6876 can be configured to use the internal 1.25V reference or an external voltage reference. REFIN is tri-stated when using the internal reference. REFIN provides the threshold voltage for the voltage detectors when using an external voltage reference.
PAGE 13
EEPROM-Programmable, Quad, Power-Supply Tracker/Sequencer Circuit PIN 32 33 NAME FUNCTION GATE2 Gate Drive for External n-Channel FETs. GATE2 begins enhancing the external n-channel FETs when all monitored inputs are within their selected thresholds (0.5V to 5.5V), at least one IN_ input or VCC is above the minimum operating voltage, VTRKEN > 1.285V threshold, and the ENABLE input is logic high.
PAGE 14
Functional Diagram IN1 IN2 ABP IN3 VCC IN4 ABP GATE1 OUT1 VCP1 = VIN1 + 5V INTERNAL SUPPLY/UVLO MAX6876 CHARGE PUMP IN1 UV/OV IN1 COMP RAMP GENERATOR IN2 UV/OV PG1 OVERCURRENT DETECT COMP IN1 VTHPG COMP ABP CONTROL LOGIC IN3 UV/OV GND COMP RAMP IN4 UV/OV TRACKING MONITORS 1.
PAGE 15
EEPROM-Programmable, Quad, Power-Supply Tracker/Sequencer Circuit MAX6876 Table 1. Master/Slave Settings REGISTER ADDRESS EEPROM MEMORY ADDRESS BIT RANGE DESCRIPTION If “00,” the device configuration is a single device. 09h 29h [7:6] If “01,” the device configuration is multiple devices, slave. If “10,” the device configuration is multiple devices, slave. If “11,” the device configuration is multiple devices, master.
PAGE 16
MAX6876 EEPROM-Programmable, Quad, Power-Supply Tracker/Sequencer Circuit catch up. When the slave’s voltages approach the ramp voltage, the slave releases HOLD and the master allows the ramp voltage to begin rising again. All tracking must be completed by the selected tracking fault timeout period or the supplies are powered down. The slave HOLD output is asserted low until the selected tracking IN_ voltages are within their selected thresholds.
PAGE 17
EEPROM-Programmable, Quad, Power-Supply Tracker/Sequencer Circuit MAX6876 Table 2.
PAGE 18
MAX6876 EEPROM-Programmable, Quad, Power-Supply Tracker/Sequencer Circuit Table 3.
PAGE 19
EEPROM-Programmable, Quad, Power-Supply Tracker/Sequencer Circuit MAX6876 Table 5. Program Autoretry/Latch off REGISTER ADDRESS EEPROM MEMORY ADDRESS BIT RANGE 5 DESCRIPTION If 1, latch-on fault If 0, autoretry “000” autoretry timer value = 25µs “001” autoretry timer value = 12.5ms 09h “010” autoretry timer value = 25.0ms 29h [4:2] “011” autoretry timer value = 50.0ms “100” autoretry timer value = 100.0ms “101” autoretry timer value = 200.0ms “110” autoretry timer value = 400.
PAGE 20
MAX6876 EEPROM-Programmable, Quad, Power-Supply Tracker/Sequencer Circuit Table 6. IN1–IN4 Threshold Settings (continued) REGISTER ADDRESS 05h 06h 07h EEPROM MEMORY ADDRESS 25h 26h 27h BIT RANGE DESCRIPTION [7:0] IN2 Overvoltage Threshold VTH = 1.0 + n x 20mV (if R08[6] = 0) VTH = 0.5 + n x 10mV (if R08[6] = 1) where n is the register content decimal representation. Note that VTH ranges must be 1V to 5.5V and 0.5V to 3.05V, respectively. [7:0] IN3 Overvoltage Threshold VTH = 1.
PAGE 21
EEPROM-Programmable, Quad, Power-Supply Tracker/Sequencer Circuit MAX6876 Table 7. Program ENABLE REGISTER ADDRESS EEPROM MEMORY ADDRESS BIT RANGE DESCRIPTION Bit 1—If 1, check ENABLE with I2C enable control bit If 0, ignore ENABLE with I2C 09h 29h [1:0] Bit 0—If 0, enable with I2C = 0, I2C enable command bit If 1, enable with I2C = 1 Table 8.
PAGE 22
MAX6876 EEPROM-Programmable, Quad, Power-Supply Tracker/Sequencer Circuit Table 9. GATE-Delay Time Settings REGISTER ADDRESS EEPROM MEMORY ADDRESS BIT RANGE DESCRIPTION “000” gate-delay timer value = 25µs “001” gate-delay timer value = 12.5ms “010” gate-delay timer value = 25.0ms 0Fh 2Fh “011” gate-delay timer value = 50.0ms [7:5] “100” gate-delay timer value = 100.0ms “101” gate-delay timer value = 200.0ms “110” gate-delay timer value = 400.0ms “111” gate-delay timer value = 1600.0ms Table 10.
PAGE 23
EEPROM-Programmable, Quad, Power-Supply Tracker/Sequencer Circuit MAX6876 Table 11. PG Threshold Settings REGISTER ADDRESS EEPROM MEMORY ADDRESS BIT RANGE DESCRIPTION “00” IN4 to OUT4 power-good threshold = 95% [7:6] “01” IN4 to OUT4 power-good threshold = 92.5% “10” IN4 to OUT4 power-good threshold = 90% “11” IN4 to OUT4 power-good threshold = 87.5% “00” IN3 to OUT3 power-good threshold = 95% "01" IN3 to OUT3 power-good threshold = 92.
PAGE 24
MAX6876 EEPROM-Programmable, Quad, Power-Supply Tracker/Sequencer Circuit Table 12. OC Threshold Settings REGISTER ADDRESS EEPROM MEMORY ADDRESS BIT RANGE [7:6] DESCRIPTION Bit [7:6] “00” IN4 to OUT4 overcurrent threshold = 97.5% “01” IN4 to OUT4 overcurrent threshold = 95% “10” IN4 to OUT4 overcurrent threshold = 92.5% “11” IN4 to OUT4 overcurrent threshold = 90% Bit [5:4] “00” IN3 to OUT3 overcurrent threshold = 97.
PAGE 25
EEPROM-Programmable, Quad, Power-Supply Tracker/Sequencer Circuit REGISTER ADDRESS EEPROM MEMORY ADDRESS BIT RANGE MAX6876 Table 13.
PAGE 26
MAX6876 EEPROM-Programmable, Quad, Power-Supply Tracker/Sequencer Circuit Table 14. Registers Summary REGISTERS DESCRIPTIONS Input Undervoltage Thresholds (Registers 00h to 03h) Input undervoltage thresholds (0.5V to 3.04V in 10mV increments or 1.0V to 5.5V in 20mV increments). Each channel’s range is selected with register 08h. Input Overvoltage Thresholds (Registers 04h to 07h) Input overvoltage thresholds (0.5V to 3.04V in 10mV increments or 1.0V to 5.5V in 20mV increments).
PAGE 27
EEPROM-Programmable, Quad, Power-Supply Tracker/Sequencer Circuit MAX6876 SDA tBUF tSU:DAT tSU:STA tHD:DAT tLOW tHD:STA tSU:STO SCL tHIGH tHD:STA tR tF START CONDITION STOP CONDITION REPEATED START CONDITION START CONDITION Figure 10. Serial-Interface Timing Details SDA SDA SCL SCL DATA LINE STABLE, CHANGE OF DATA ALLOWED DATA VALID S P START CONDITION STOP CONDITION Figure 11. Bit Transfer Figure 12.
PAGE 28
MAX6876 EEPROM-Programmable, Quad, Power-Supply Tracker/Sequencer Circuit START CONDITION CLOCK PULSE FOR ACKNOWLEDGE 2 1 SCL 8 9 SDA BY TRANSMITTER S SDA BY RECEIVER Figure 13. Acknowledge Slave Address The MAX6876 slave address conforms to the following table: SA7 (MSB) SA6 SA5 SA4 SA3 SA2 SA1 SA0 (LSB) 1 0 1 0 A1 A0 X R/W X = Don’t care. SA7–SA4 represent the standard 2-wire interface address (1010) for devices with EEPROM.
PAGE 29
EEPROM-Programmable, Quad, Power-Supply Tracker/Sequencer Circuit START 1 0 1 0 MSB A1 A0 X R/W MAX6876 SDA ACK LSB SCL Figure 14. Slave Address 8) The master sends a stop condition or sends another 8-bit data byte. 9) The addressed slave asserts an ACK on SDA. 10) The master sends a stop condition. To write a single byte to the register bank, only the 8-bit command code and a single 8-bit data byte are sent.
PAGE 30
MAX6876 EEPROM-Programmable, Quad, Power-Supply Tracker/Sequencer Circuit SEND BYTE FORMAT S WRITE WORD FORMAT ADDRESS WR 7 bits 0 ACK DATA ACK P S 8 bits Slave Address– equivalent to chipselect line of a 3wire interface. Data Byte–presets the internal address pointer. ADDRESS WR 7 bits 0 ACK COMMAND ACK DATA 8 bits Slave Address– equivalent to chipselect line of a 3wire interface. ACK DATA 8 bits Write Address of the register you are writing to.
PAGE 31
EEPROM-Programmable, Quad, Power-Supply Tracker/Sequencer Circuit REGISTER ADDRESS EEPROM MEMORY ADDRESS BIT RANGE 13h 33h 2 DESCRIPTION If 1, configuration registers are locked If 0, configuration registers unlocked 6) The master generates a repeated start condition. 7) The master sends the 7-bit slave address and a read bit (high). 8) The slave asserts an ACK on SDA. 9) The slave sends the 8-bit byte count (16). 10) The master asserts an ACK on SDA. 11) The slave sends 8 bits of data.
PAGE 32
MAX6876 EEPROM-Programmable, Quad, Power-Supply Tracker/Sequencer Circuit Table 16. Register Map REGISTER ADDRESS 00h 01h 02h 03h 04h 05h 06h 32 EEPROM MEMORY ADDRESS 20h 21h 22h 23h 24h 25h 26h READ/WRITE DESCRIPTION R/W IN1 Undervoltage Threshold Value (VTH): VTH = 1.0 + n x 20mV (if R08[7] = 0) VTH = 0.5 + n x 10mV (if R08[7] = 1) where n is the register content decimal representation. Note that VTH ranges must be 1V to 5.5V and 0.5V to 3.05V, respectively.
PAGE 33
EEPROM-Programmable, Quad, Power-Supply Tracker/Sequencer Circuit REGISTER ADDRESS 07h EEPROM MEMORY ADDRESS 27h READ/WRITE R/W MAX6876 Table 16. Register Map (continued) DESCRIPTION IN4 Overvoltage Threshold Value (VTH): VTH = 1.0 + n x 20mV (if R08[4] = 0) VTH = 0.5 + n x 10mV (if R08[4] = 1) where n is the register content decimal representation. Note that VTH ranges must be 1V to 5.5V and 0.5V to 3.05V, respectively.
PAGE 34
MAX6876 EEPROM-Programmable, Quad, Power-Supply Tracker/Sequencer Circuit Table 16.
PAGE 35
EEPROM-Programmable, Quad, Power-Supply Tracker/Sequencer Circuit REGISTER ADDRESS EEPROM MEMORY ADDRESS READ/WRITE MAX6876 Table 16. Register Map (continued) DESCRIPTION Bit [7:6] “00” overcurrent timer value = 12.
PAGE 36
MAX6876 EEPROM-Programmable, Quad, Power-Supply Tracker/Sequencer Circuit Table 16.
PAGE 37
EEPROM-Programmable, Quad, Power-Supply Tracker/Sequencer Circuit MAX6876 Table 16. Register Map (continued) REGISTER ADDRESS EEPROM MEMORY ADDRESS READ/WRITE 17h 37h — 18h 38h — 19h 39h — 1Ah 3Ah — 1Bh 3Bh — 1Ch 3Ch — DESCRIPTION Reserved. Should not be overwritten. Reserved. Should not be overwritten. Reserved. Should not be overwritten. Reserved. Should not be overwritten. Reserved. Should not be overwritten. Reserved. Should not be overwritten. Reserved. Should not be overwritten.
PAGE 38
EEPROM-Programmable, Quad, Power-Supply Tracker/Sequencer Circuit MAX6876 Typical Application Circuits IN1 OUT1 IN2 OUT2 IN3 OUT3 IN4 OUT4 IN1 IN2 IN3 VCC IN4 GATE1 GATE2 GATE3 GATE4 OUT1 OUT2 FAULT OUT3 HOLD MAX6876 SYNCH OUT4 ENABLE ABP IN1 REM GND SDA 5V IN2 3.0V 1.8V IN3 IN4 1V IN1 IN2 IN3 VPULLUP RESET TRKEN SCL A0 A1 OUT1 IN5 OUT2 IN6 OUT3 IN7 OUT4 IN8 IN4 GATE1 GATE2 GATE3 GATE4 OUT1 OUT2 OUT3 OUT4 SYNCH (OUT) PG_ OUT5 3.3V OUT6 2.5V 1.
PAGE 39
EEPROM-Programmable, Quad, Power-Supply Tracker/Sequencer Circuit QFN THIN 6x6x0.8.EPS D2 D CL D/2 b D2/2 k E/2 E2/2 (NE-1) X e E CL E2 k e L (ND-1) X e e L CL CL L1 L L e A1 A2 e A PACKAGE OUTLINE 36, 40, 48L THIN QFN, 6x6x0.8mm 21-0141 E 1 2 NOTES: 1. DIMENSIONING & TOLERANCING CONFORM TO ASME Y14.5M-1994. 2. ALL DIMENSIONS ARE IN MILLIMETERS. ANGLES ARE IN DEGREES. 3. N IS THE TOTAL NUMBER OF TERMINALS. 4.