Rainbow Electronics MAX847 User Manual

________________General Description

The MAX847 is a complete power-supply and monitor­ing system for two-way pagers or other low-power digi­tal communications devices. It requires few external
components. Included on-chip are:

• A 1-cell input, 80mA output, synchronous-rectified
boost DC-DC regulator with a digitally controlled
+1.8V to +4.9V output

• Three low-noise linear-regulator outputs

• Three DAC-controlled comparators for software­driven 3-channel A/D conversion

• SPI™-compatible serial interface

• Reset and low-battery (LBO) warning outputs

• Charger for NiCd, NiMH, lithium battery, or storage
capacitor for RF PA power or system backup

• Two 1.8Ω (typical) serial-controlled open-drain
MOSFET switches

An evaluation kit for the MAX847 (MAX847EVKIT) is
available to aid in design and prototyping.

Pin Configuration appears at end of data sheet.

____________________________Features

♦ 80mA Output from 1 Cell at 90% Efficiency
♦ 13µA Idle Mode™ (coast) Current
♦ Selectable Low-Noise PWM or Low-Current

Operation

♦ PWM Operating Frequency Synchronized to

Seven Times an External Clock Source

♦ Operates at 270kHz with No External Clock
♦ Automatic Backup-Battery Switchover

________________________Applications

Two-Way Pagers
GPS Receivers
1-Cell Powered Hand-Held Equipment

MAX847

1-Cell, Step-Up

Two-Way Pager System IC

________________________________________________________________

Maxim Integrated Products

1

MAX847

INPUT

SINGLE AA

ALKALINE BATTERY

0.8V TO 1.8V

BATT

LX1

OUT

PGND

REG2IN

OFS

REG1

OUTPUT 2

2.85V ANALOG

LOW-BATTERY

IN/OUT

RESET

IN/OUT

SERIAL

I/O

1.8Ω

DRIVERS

A/D INPUT

OPTIONAL

OUTPUT 1
3V LOGIC

OUTPUT 3
1V RECEIVER

TO RF PA

NiCd BATTERY STACK
OR
STORAGE CAPACITOR

REG2

REG3

NICD

AGNDREFFILT

LBI
LBO

RSIN
RSO

CS
SCL

SDI
SDO

DR1
DR2
DR2IN

DRGND

CH0
SYNC

RUN

COAST

RUN

____________________________________________________Typical Operating Circuit

PART

MAX847EEI -40°C to +85°C

TEMP. RANGE PIN-PACKAGE

28 QSOP

19-1349; Rev 1a; 10/98

Ordering Information

Idle Mode is a trademark of Maxim Integrated Products. SPI is a trademark of Motorola, Inc.

For free samples & the latest literature: http://www.maxim-ic.com, or phone [phone].
For small orders, phone [phone].

EVALUATION KIT MANUAL

FOLLOWS DATA SHEET

MAX847

1-Cell, Step-Up
Two-Way Pager System IC

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(OUT = 3.0V, BATT = 1.2V, NICD = 3.6V, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.

BATT, OUT, NICD, LBO, RSO to AGND...................-0.3V to +6V

REG1, OFS, REG2, REF, R2IN to AGND...-0.3V to (OUT + 0.3V)
SCL, SDO, SDI,

CS , SYNC, FILT, DR2IN,

CH0, LBI, RSIN, RUN to AGND...................-0.3V to (REG1 + 0.3V)

REG3 .......................................................-0.3V to (REG2 + 0.3V)

DR1, DR2 to DRGND ...............................-0.3V to (BATT + 0.3V)

PGND, DRGND to AGND......................................-0.3V to +0.3V

LX1 to PGND .............................................-0.3V to (OUT + 0.3V)

Continuous Power Dissipation (T

A

= +70°C)

28-Pin QSOP (derate 8mW/°C above +70°C) .............640mW

Operating Temperature Range ...........................-40°C to +85°C

Junction Temperature......................................................+150°C

Storage Temperature Range.............................-65°C to +165°C

Lead Temperature (soldering, 10sec).............................+300°C

T

A

= +25°C

Run or Coast Mode

Incremental supply current when on

REG2, REG3 and CH DAC off, V

OUT

= 2.8V
REG2, REG3 and CH DAC on
Coast mode

Incremental supply current when on

CONDITIONS

V0.9 1.1

BATT Minimum Start-Up Voltage
(Note 3)

V

0.8

OUT x

0.8

BATT Typical Operating Range
(Note 2)

µA30CH DAC Supply Current (Note 4)

µA13 25Coast Mode Supply Current (Note 4)
µA875 1350Run Mode Supply Current (Note 4)
µA0.5 2BATT Supply Current (Note 5)

µA20REG3 Supply Current (Note 4)

UNITSMIN TYP MAXPARAMETER

I

REF

= 0 to 20µA, OUT = 1.8V to 4.9V V-1.5% 1.28 1.5%Reference Voltage

IDR= 120mA

Ω

1.8 2.8

DR1, DR2 On-Resistance

VDR= 5V nA1 250DR1, DR2 Leakage Current

TA= +25°C
TA= -40°C to +85°C

I

SDO

= 100µA mV200SDO Output Low

I

SDO

= -100µA, from REG1 V

V

REG1

- 0.2

SDO Output High

Includes CS, SDI, SCL, DR2IN, SYNC, and RUN

V0.4Logic Input Level Low

Includes CS, SDI, SCL, DR2IN, SYNC, and RUN

V

V

REG1

- 0.4

Logic Input Level High

3.6

50% duty cycle MHz5SCL Maximum Clock Rate

ns100SDI Setup Time, t

DS

ns50SDI Hold Time, t

DH

Logic Input = 0 to 3.3V; includes CS, SDI, SCL,
DR2IN, SYNC, and RUN

µA-1 1Logic Input Current

Charger and Backup Modes off, NICD = 3.6V µA1.2 3

NICD Input Current, Standby
(Note 6)

Incremental supply current when on µA

Backup mode, NICD = 3.6V, OUT = 3V

50REG2 Supply Current (Note 4)

µA20 40

NICD Input Supply Current, Backup
(Note 7)

Charger and Backup Modes off,
BATT = 0V and OUT = 0V

µA1.2 3

NICD Input Current, Power Fail
(Note 8)

GENERAL PERFORMANCE

SERIAL-INTERFACE TIMING SPECIFICATIONS (Note 9)

MAX847

1-Cell, Step-Up

Two-Way Pager System IC

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(OUT = 3.0V, BATT = 1.2V, NICD = 3.6V, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)

%-3.5 3.5

OUT Error, Coast Mode
(Note 11)

I

OUT

= 1mA to 80mA, Run Mode mV25OUT Load Regulation

Coast Mode, OUT = 1.8V to 4.9V

Circuit of Figure 2, OUT = 3.0V, BATT = 1.1V

Circuit of Figure 2, OUT = 3.0V, BATT = 1.0V

CONDITIONS

BATT = 0.8V to 1.5V mV25OUT Line Regulation

LX1

Ω

0.45 0.9

LX1 On-Resistance

ns100

CS Pulse Width High, t

CSW

ns70SCL to SDO Output Valid, t

DO

ns50

SCL Pulse Width High or Low,
tCH, t

CL

mA80 115

Output Current, Run Mode
(Note 10)

mA15 40

Output Current, Coast Mode
(Note 10)

UNITSMIN TYP MAXPARAMETER

NMOS
PMOS 0.65 1.3

TA= +25°C, FILT connected to REF kHz210 270 325Frequency, Free-Run
f

SYNC

= 38.4kHz kHz268.8Frequency, Locked

f

SYNC

= 38.4kHz, FILT network = 1nF(22nF + 10kΩ)

kHz±15Jitter (Note 14)

f

SYNC

= 38.4kHz, FILT network = 1nF



(22nF + 10kΩ)

ms1 25Capture Time (Note 14)

0.2V < (OUT - NICD) < 2V, 15mA_CHG = 1 mA7 25Current High

0.2V < (OUT - NICD) < 2V, 1mA_CHG = 1 mA0.45 1.5Current Low
OUT = 2.8V, I

OUT

= 20mA, NICD = 3.3V %-3.5 3.5OUT Error, Backup Regulator

Backup Mode, NICD = 3.3V

Ω

5 10

Backup-Regulator
On-Resistance (Note 15)

ns70

CS to SDO Disable, t

TR

%-3.5 3.5

OUT Error, Run Mode
(Note 12)

Run Mode, OUT = 1.8V to 4.9V

mV30 100 170

OUT DAC Step Size
(Note 13)

Coast or Run Mode,
OUT = 1.8V to 4.9V

ns50
ns50

CS to SCL Hold Time, t

CSH

CS to SCL Setup Time, t

CSS

ns70

CS to SDO Output Valid, t

DV

OUT = 3.0V %76 83Maximum LX1 Duty Cycle
I

OUT

= 80mA, C

OUT

= 47µF with ESR < 0.25Ω

mVp-p70OUT Voltage Ripple

During the inductor charge cycle mA480 600 720LX1 Switch Current Limit

DC-DC CONVERTER

PHASE-LOCKED LOOP (PLL)

NICD CHARGER

MAX847

1-Cell, Step-Up
Two-Way Pager System IC

4 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (continued)

(OUT = 3.0V, BATT = 1.2V, NICD = 3.6V, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)

I

REG2

= 0 to 24mA, OUT = 3.0V, R

OFS

= 15kΩ

mV120 155 190REG2 Voltage Drop

OUT = 3.0V, I

REG1

= 65mA

f = 268.8kHz, C

REG1

= 10µF ceramic

CONDITIONS

f = 268.8kHz, C

REG1

= 10µF, ceramic,

R

OFS

= 15kΩ, C

OFS

= 0.1µF, I

REG2

= 15mA

dB30 40

REG2 Supply Rejection
(Note 15)

f = 268.8kHz, C

REG1

= 1µF ceramic dB40 50REG3 Supply Rejection (Note 15)

nA-50 -3 50LBI/RSIN Input Current

I

OUT

= 1mA mV30 400LBO/RSO Output Low

Output = 5.5V nA1 250LBO/RSO Output Leakage

Ω

1.5 3.1REG1 PMOS On-Resistance
dB15 25REG1 Supply Rejection (Note 15)

UNITSMIN TYP MAXPARAMETER

10mV overdrive µs15 50

LBO/RSO Response Time
(Note 15)

V0.2 1.27CH0 Threshold Range (Note 15)
Measures NICD V1.2 5.08CH1 Threshold Range (Note 15)
Measures BATT V0.2 1.27CH2 Threshold Range (Note 15)

mV10

CH0 Threshold Resolution
(Note 15)

Measures NICD mV40

CH1 Threshold Resolution
(Note 15)

Measures BATT mV10

CH2 Threshold Resolution
(Note 15)

mV7.5 16 30

LBI/RSIN Input Hysteresis
(Note 15)

I

REG2

= 0.1mA to 24mA mV9REG2 Load Regulation

REG3 Output Voltage I

REG3

= 0 to 2mA 0.96 1.0 1.04 V

Falling input V0.58 0.60 0.63LBI/RSIN Input Threshold

At thresholds of 200mV, 800mV, and 1270mV %

-2.0 2.0

-15mV +15mV

CH0 Error

At thresholds of 1200mV, 3200mV, and 5080mV %

-3.0 3.0

-60mV +60mV

CH1 Error

3.2 3.3 3.4

I

OUT

= 1mA, OUT = 4.9V V

3.15 3.45

REG1 Clamp Voltage

TA= +25°C
TA= -40°C to +85°C

At thresholds of 200mV, 800mV, and 1270mV %

-2.0 2.0

-15mV +15mV

CH2 Error

mV1 2 4CH0 Input Hysteresis (Note 15)

LINEAR REGULATORS

DATA-ACQUISITION AND VOLTAGE MONITORS

mV4 8 16CH1 Input Hysteresis (Note 15)

MAX847

1-Cell, Step-Up

Two-Way Pager System IC

_______________________________________________________________________________________ 5

ELECTRICAL CHARACTERISTICS (continued)

(OUT = 3.0V, BATT = 1.2V, NICD = 3.6V, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)

CONDITIONS

mV1 2 4CH2 Input Hysteresis (Note 15)

UNITS

MIN TYP MAXPARAMETER

CH0 = 0.2V to 1.27V nA-100 100CH0 Input Current
10mV overdrive µs0.6 1.0

CH Comparator Response Time
(Note 15)

Note 1: Specifications to -40°C are guaranteed by design, not production tested.
Note 2: This is not a tested parameter, since the IC is powered from OUT, not BATT. The only limitation in the BATT range is the

inability to generate more than 5 times, or less than 1.15 times the BATT voltage at OUT. This is due to PWM controller
duty-cycle limitations in Run Mode.

Note 3: Minimum start-up voltage is tested by determining when the LX pins can draw at least 50mA for 1µs (min) at a 50kHz (min)

repetition rate. This guarantees that the IC will deliver at least 200µA at the OUT pin.

Note 4: This supply current is drawn from the OUT pin. Current drain from the battery depends on voltages at BATT and OUT and

on the DC-to-DC converter’s efficiency.

Note 5: Current into BATT pin in addition to the supply current at OUT. This current is roughly constant from Coast to Run Mode.
Note 6: Current into NICD pin when NICD isn’t being charged and isn’t regulating OUT.
Note 7: Current into NICD pin when NICD is regulating OUT. Doesn’t include current drawn from OUT by the rest of the circuit.

Measured by setting the OUT regulation point to 2.8V and holding OUT at 3.0V.

Note 8: Current into NICD pin when BATT and OUT are both at 0V. This test guarantees that NICD won’t draw significant current

when the main battery is removed and backup is not activated.

Note 9: Serial-interface timing specifications are not tested and are provided for design guidance only. Serial-interface functionali-

ty is tested by clocking data in at 5MHz with a 50% duty-cycle clock and checking for proper operation. With OUT set
below 2.5V, the serial-interface clock frequency should be reduced to 1MHz to ensure proper operation.

Note 10: This specification is not directly tested but is guaranteed by correlation to LX on-resistance and current-limit tests.
Note 11: Measured by using the internal feedback network and Coast-Mode error comparator to regulate OUT. Doesn’t include

ripple voltage due to inductor currents.

Note 12: Measured by using the internal feedback network and Run-Mode error comparator to regulate OUT. Doesn’t include ripple

voltage due to inductor currents.

Note 13: Uses the OUT measurement techniques described for the OUT Error, Coast Mode, and OUT Error Run Mode specifications.
Note 14: PLL acquisition characteristics depend on the impedance at the FILT pin. The specification is not tested and is provided

for design guidance only.

Note 15: The limits in this specification are not guaranteed and are provided for design guidance only.

__________________________________________Typical Operating Characteristics

(Circuit of Figure 2, TA= +25°C, unless otherwise noted.)

100

40

1 1000

EFFICIENCY vs. LOAD CURRENT

(RUN MODE, V

OUT

= 3.0V)

60

50

80

90

70

MAX847TOC01

LOAD CURRENT (mA)

EFFICIENCY (%)

10 100

VIN = 2.0V

VIN = 0.8V

VIN = 1.0V

VIN = 1.2V

VIN = 1.5V

EFFICIENCY vs. LOAD CURRENT

(COAST MODE, V

OUT

= 3.0V)

MAX847TOC02

LOAD CURRENT (mA)

EFFICIENCY (%)

100 1000

40

50

60

80

70

90

100

0.1 1 10

VIN = 2.0V

VIN = 0.8V

VIN = 1.0V

VIN = 1.2V

VIN = 1.5V

EFFICIENCY vs. LOAD CURRENT

(COAST MODE, V

OUT

= 2.4V)

MAX847TOC03

LOAD CURRENT (mA)

EFFICIENCY (%)

100 1000

40

50

60

80

70

90

100

0.1 1 10

VIN = 2.0V

VIN = 0.8V

VIN = 1.0V

VIN = 1.2V

VIN = 1.5V

MAX847

1-Cell, Step-Up
Two-Way Pager System IC

6 _______________________________________________________________________________________

Typical Operating Characteristics (continued)

(Circuit of Figure 2, TA= +25°C, unless otherwise noted.)

0

20

60

40

80

100

0.5 1 1.5 2

NO-LOAD BATTERY CURRENT

vs. BATTERY VOLTAGE

MAX847-toc04

BATTERY VOLTAGE (V)

BATTERY CURRENT (mA)

V

OUT

= 3.0V

COAST MODE

0

100

50

200

150

250

300

0 10.5 1.5 2 2.5

MAXIMUM LOAD CURRENT vs.

BATTERY VOLTAGE

MAX847-TOC05

BATTERY VOLTAGE (V)

MAXIMUM LOAD CURRENT (mA)

RUN MODE

COAST MODE

(V

OUT

= 3.0V)

1 10 100

START-UP INPUT VOLTAGE

vs. LOAD CURRENT

MAX847-TOC06

LOAD CURRENT (mA)

INPUT VOLTAGE (V)

0

0.6

0.4

0.2

0.8

1.0

1.2

1.4

1.6

1.8

2.0

V

OUT

= 3.0V

COAST MODE

0

5

15

10

20

25

0 21 3 4 5 6

NICD CHARGING CURRENT vs.

NICD VOLTAGE

MAX847-TOC7

OUTPUT VOLTAGE (V)

NICD CHARGING CURRENT (mA)

15mA MODE
V

OUT

= 4.9V

20

-80
100 200 300 400 500 600

LX NOISE SPECTRUM

(RUN MODE, SYNC OPERATION)

-60

MAX847-09

FREQUENCY (kHz)

NOISE (dBV)

-40

-20

0

0

2

1

3

0 21 3 4 5

DR1 OR DR2 ON-RESISTANCE vs. V

OUT

MAX847-toc08

V

OUT

VOLTAGE (V)

R

ON

(Ω)

100

0

0.1 1 10 100 1000 10,000

REG2 NOISE SPECTRUM

(RUN MODE)

20

MAX847TOC-10

FREQUENCY (kHz)

NOISE (dBµV)

40

60

80