Manual

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________________General Description

The MAX847 is a complete power-supply and monitor-

ing system for two-way pagers or other low-power digi-

tal 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 software-

driven 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

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

STORAGE CAPACITOR

REG2

REG3

NICD

AGNDREFFILT

LBI

LBO

RSIN

RSO

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 1-800-998-8800.

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

EVALUATION KIT MANUAL

FOLLOWS DATA SHEET

Summary of content (18 pages)

PAGE 1
9-1349; Rev 1a; 10/98 L MANUA ION KIT HEET T A U L EVA TA S WS DA FOLLO 1-Cell, Step-Up Two-Way Pager System IC ____________________________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 Ordering Information • Charger for NiCd, NiMH, lithium battery, or
PAGE 2
MAX847 1-Cell, Step-Up Two-Way Pager System IC ABSOLUTE MAXIMUM RATINGS 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 ..............................
PAGE 3
1-Cell, Step-Up Two-Way Pager System IC MAX847 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.
PAGE 4
MAX847 1-Cell, Step-Up Two-Way Pager System IC 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) PARAMETER CONDITIONS LINEAR REGULATORS REG1 PMOS On-Resistance OUT = 3.0V, IREG1 = 65mA REG1 Supply Rejection (Note 15) f = 268.8kHz, CREG1 = 10µF ceramic REG1 Clamp Voltage IOUT = 1mA, OUT = 4.9V TA = +25°C REG2 Voltage Drop TA = -40°C to +85°C IREG2 = 0 to 24mA, OUT = 3.
PAGE 5
1-Cell, Step-Up Two-Way Pager System IC MAX847 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) PARAMETER CONDITIONS CH2 Input Hysteresis (Note 15) CH0 Input Current CH0 = 0.2V to 1.
PAGE 6
Typical Operating Characteristics (continued) (Circuit of Figure 2, TA = +25°C, unless otherwise noted.) MAXIMUM LOAD CURRENT vs. BATTERY VOLTAGE 60 40 20 250 1.5 100 COAST MODE 1.6 1.2 1.0 0.8 0.6 0.4 50 VOUT = 3.0V COAST MODE 0.2 0 0 0 2 0.5 1 1.5 2 1 2.5 10 BATTERY VOLTAGE (V) BATTERY VOLTAGE (V) NICD CHARGING CURRENT vs. NICD VOLTAGE DR1 OR DR2 ON-RESISTANCE vs. VOUT MAX847-toc08 20 LOAD CURRENT (mA) 3 MAX847-TOC7 25 2 15 RON (Ω) NICD CHARGING CURRENT (mA) 1.8 1.
PAGE 7
1-Cell, Step-Up Two-Way Pager System IC PIN NAME FUNCTION 1 LX1 Connect LX1 to the inductor. LX1 is internally connected to an NFET that switches to PGND and a PFET that switches to OUT. 2 SDI Serial Data Input for SPI Interface 3 SDO Serial Data Output for SPI Interface 4 PGND 5 SCL Serial Clock for SPI Interface 6 LBO Open-Drain Output for LBI Comparator 7 RSO Reset Output. Open drain goes low when RSIN drops below 0.6V. All serial registers are reset (or set) to POR state as well.
PAGE 8
MAX847 1-Cell, Step-Up Two-Way Pager System IC 1-CELL BATTERY IN SCL SDI 5 SDO 2 3 CS 27 28 26 N LBO LBI PWM (PFM IN COAST) – 0.6V CPLB + RUN/ COAST LBO CH0 9 + CP0 – FROM NICD S1 + CP2 – 4 5 – AR1 + REG1 24 10µF BACKUP REGULATOR – AOUT + V FEEDBACK 1.28V REFERENCE 10 47µF P CONTROL CHARGE NICD OR BACKUP REGULATOR 1µF RSIN OUT 25 3.3V CLAMP 8 0.
PAGE 9
1-Cell, Step-Up Two-Way Pager System IC The MAX847 contains several functional blocks that simplify the integration of power-supply and monitoring functions within a 1-cell powered system. They are described in the following subsections. Voltage Regulators Regulator outputs include the following: • OUT: Main switch-mode boost output • REG1: 1.5Ω switch and output voltage clamp. Switches REG1 to OUT and clamps REG1 at 3.3V when OUT is set to 3.4V or more.
PAGE 10
MAX847 1-Cell, Step-Up Two-Way Pager System IC OUT can be set as low as 1.8V; however, some run mode functions are limited when VOUT is below 2.5V: • The allowed serial-interface clock rate is reduced. • Internal LX FET and DR1 and DR2 on-resistance increases. Logic Supply (REG1) REG1 is not a regulator in the conventional sense, but rather a 1.5Ω PFET that acts as either a switch or a voltage clamp, depending on the programmed OUT voltage. When OUT is set to 3.3V or less, REG1 operates as a switch.
PAGE 11
1-Cell, Step-Up Two-Way Pager System IC MAX847 Table 1. Run and Coast Mode Start-Up Requirements SYNC OPERATION No SYNC clock is used. CIRCUIT CONNECTION 1) Connect REF to FILT 2) Remove R7, C9, and C10 START-UP MODE CAPABILITY Can start in either Coast or Run Mode by tying RUN pin appropriately. In Run Mode the DC-DC converter operates at 270kHz. Use standard Figure 2 circuit Can start in either Coast or Run Mode by tying RUN pin appropriately.
PAGE 12
MAX847 1-Cell, Step-Up Two-Way Pager System IC pulse width modulation (PWM), as well as synchronization, to minimize noise. Some MAX847 functions are confined to Run Mode while others remain active in both Run and Coast. These are outlined as follows. Various circuit functions can be disabled as follows: Functions that always remain on are: • Serial I/O • Reference (REF) • OUT • REG1 • LBI, RSIN (and LBO, RSO) Power-On Reset The MAX847 has an internal POR circuit (VOUT < 1.
PAGE 13
1-Cell, Step-Up Two-Way Pager System IC Automatic Backup Setting the LBO_Sets_BACKUP serial bit (Table 2) programs the IC so that when LBO goes low, the backup regulator automatically turns on without instructions from the microprocessor (µP). When the LBO_ Sets_BACKUP bit is 0, the backup regulator is turned on only by setting the BACKUP bit. The BACKUP bit also overrides the LBO_Sets_BACKUP bit. Figure 4 shows the logic for this function.
PAGE 14
MAX847 1-Cell, Step-Up Two-Way Pager System IC ••• CS tCSH tCSS tCL tCH SCLK tCSH ••• tDS tDH ••• DIN tDV tDO tTR ••• DOUT Figure 5. Detailed Serial-Interface Timing CS SCL SDO SDI D7 R2 D6 D5 D4 0 0 R1 R0 D4 D3 D2 0 0 D1 D0 Figure 6. CS, SCL, SDO, and SDI Serial Timing Serial data is clocked in and out MSB first. Input data is latched on the CLK rising edge, and output data is shifted out on the CLK falling edge.
PAGE 15
1-Cell, Step-Up Two-Way Pager System IC D7 (MSB) D6 CH2_OUT D5 CH1_OUT D4 CH0_OUT LBO Table 6. VOUT Output Voltage SERIAL-DATA BIT VOUT (V) D3–D0 X FUNCTION CH_ OUT and LBO output bits. A 1 indicates that the selected channel (CH_) voltage is greater than the CH DAC voltage or that LBI is less than 0.6V. lation of programming etiquette (R1 and R0 are sometimes address bits and other times data bits) allows the CH DAC to be loaded with only one write operation.
PAGE 16
MAX847 1-Cell, Step-Up Two-Way Pager System IC Table 7. External Components SUPPLIER PART NO. COMMENTS INDUCTORS (22µH) DT1608C-223 0.16Ω, 3.18mm high, shielded LQH4N220K 0.94Ω, 2.6mm high, low current, low cost LQH3C221 0.71Ω, 2mm high, low current, low cost CD54-220 0.18Ω, 4.5mm high CD43-220 0.378Ω, 3.2mm high CDRH62B-220 0.34Ω, 3mm high, shielded TDK NLC565050-220K 0.
PAGE 17
1-Cell, Step-Up Two-Way Pager System IC QSOP.
PAGE 18
MAX847 1-Cell, Step-Up Two-Way Pager System IC NOTES 18 ______________________________________________________________________________________