19-1349; Rev 1a; 10/98
ANUAL
N KIT M EET
ATIO
SH
EVALU
S DATA
OLLOW
F
1-Cell, Step-Up
Two-Way Pager System IC
____________________________Features
o
80mA Output from 1 Cell at 90% Efficiency
o
13µA Idle Mode™ (coast) Current
o
Selectable Low-Noise PWM or Low-Current
Operation
o
PWM Operating Frequency Synchronized to
Seven Times an External Clock Source
o
Operates at 270kHz with No External Clock
o
Automatic Backup-Battery Switchover
________________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.
MAX847
Ordering Information
PART
MAX847EEI
TEMP. RANGE
-40°C to +85°C
PIN-PACKAGE
28 QSOP
________________________Applications
Two-Way Pagers
GPS Receivers
1-Cell Powered Hand-Held Equipment
____________________________________________________Typical Operating Circuit
INPUT
SINGLE AA
ALKALINE BATTERY
0.8V TO 1.8V
LOW-BATTERY
IN/OUT
RESET
IN/OUT
SERIAL
I/O
LBI
LBO
RSIN
RSO
CS
SCL
SDI
SDO
DR1
DR2
DR2IN
DRGND
BATT
LX1
OUT
PGND
REG2IN
MAX847
OFS
OUTPUT 2
2.85V ANALOG
OUTPUT 1
3V LOGIC
OUTPUT 3
1V RECEIVER
TO RF PA
NiCd BATTERY STACK
OR
STORAGE CAPACITOR
1.8Ω
DRIVERS
REG2
REG1
RUN
COAST
A/D INPUT
OPTIONAL
RUN
CH0
SYNC
FILT
REF
REG3
AGND NICD
Idle Mode is a trademark of Maxim Integrated Products. SPI is a trademark of Motorola, Inc.
________________________________________________________________
Maxim Integrated Products
1
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.
1-Cell, Step-Up
Two-Way Pager System IC
MAX847
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 ......................................-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
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.
ELECTRICAL CHARACTERISTICS
(OUT = 3.0V, BATT = 1.2V, NICD = 3.6V, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
GENERAL PERFORMANCE
BATT Typical Operating Range
(Note 2)
BATT Minimum Start-Up Voltage
(Note 3)
Coast Mode Supply Current (Note 4)
Run Mode Supply Current (Note 4)
BATT Supply Current (Note 5)
NICD Input Current, Standby
(Note 6)
NICD Input Supply Current, Backup
(Note 7)
NICD Input Current, Power Fail
(Note 8)
REG2 Supply Current (Note 4)
REG3 Supply Current (Note 4)
CH DAC Supply Current (Note 4)
Reference Voltage
DR1, DR2 On-Resistance
DR1, DR2 Leakage Current
SDO Output Low
SDO Output High
Logic Input Level Low
Logic Input Level High
Logic Input Current
Run or Coast Mode
T
A
= +25°C
REG2, REG3 and CH DAC off, V
OUT
= 2.8V
REG2, REG3 and CH DAC on
Coast mode
Charger and Backup Modes off, NICD = 3.6V
Backup mode, NICD = 3.6V, OUT = 3V
Charger and Backup Modes off,
BATT = 0V and OUT = 0V
Incremental supply current when on
Incremental supply current when on
Incremental supply current when on
I
REF
= 0 to 20µA, OUT = 1.8V to 4.9V
T
A
= +25°C
I
DR
= 120mA
T
A
= -40°C to +85°C
V
DR
= 5V
I
SDO
= 100µA
I
SDO
= -100µA, from REG1
Includes
CS,
SDI, SCL, DR2IN, SYNC, and RUN
Includes
CS,
SDI, SCL, DR2IN, SYNC, and RUN
Logic Input = 0 to 3.3V; includes
CS,
SDI, SCL,
DR2IN, SYNC, and RUN
-1
V
REG1
- 0.2
0.4
V
REG1
- 0.4
1
-1.5%
0.8
0.9
13
875
0.5
1.2
20
1.2
50
20
30
1.28
1.8
1
1.5%
2.8
3.6
250
200
OUT x
0.8
1.1
25
1350
2
3
40
3
V
V
µA
µA
µA
µA
µA
µA
µA
µA
µA
V
Ω
nA
mV
V
V
V
µA
CONDITIONS
MIN
TYP
MAX
UNITS
SERIAL-INTERFACE TIMING SPECIFICATIONS
(Note 9)
SCL Maximum Clock Rate
50% duty cycle
SDI Setup Time, t
DS
SDI Hold Time, t
DH
2
5
100
50
MHz
ns
ns
_______________________________________________________________________________________
1-Cell, Step-Up
Two-Way Pager System IC
ELECTRICAL CHARACTERISTICS (continued)
(OUT = 3.0V, BATT = 1.2V, NICD = 3.6V, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
SCL to SDO Output Valid, t
DO
CS
to SDO Output Valid, t
DV
CS
to SDO Disable, t
TR
CS
to SCL Setup Time, t
CSS
CS
to SCL Hold Time, t
CSH
CS
Pulse Width High, t
CSW
SCL Pulse Width High or Low,
t
CH
, t
CL
DC-DC CONVERTER
Output Current, Run Mode
(Note 10)
Output Current, Coast Mode
(Note 10)
OUT Error, Coast Mode
(Note 11)
OUT Error, Run Mode
(Note 12)
OUT DAC Step Size
(Note 13)
OUT Load Regulation
OUT Line Regulation
Maximum LX1 Duty Cycle
OUT Voltage Ripple
LX1 Switch Current Limit
LX1 On-Resistance
PHASE-LOCKED LOOP (PLL)
Frequency, Free-Run
Frequency, Locked
Jitter (Note 14)
Capture Time (Note 14)
NICD CHARGER
Current High
Current Low
OUT Error, Backup Regulator
Backup-Regulator
On-Resistance (Note 15)
T
A
= +25°C, FILT connected to REF
f
SYNC
= 38.4kHz
f
SYNC
= 38.4kHz, FILT network = 1nF
(22nF + 10kΩ)
f
SYNC
= 38.4kHz, FILT network = 1nF
(22nF + 10kΩ)
0.2V < (OUT - NICD) < 2V, 15mA_CHG = 1
0.2V < (OUT - NICD) < 2V, 1mA_CHG = 1
OUT = 2.8V, I
OUT
= 20mA, NICD = 3.3V
Backup Mode, NICD = 3.3V
7
0.45
-3.5
5
210
270
268.8
±15
1
25
25
1.5
3.5
10
325
kHz
kHz
kHz
ms
mA
mA
%
Ω
Circuit of Figure 2, OUT = 3.0V, BATT = 1.1V
Circuit of Figure 2, OUT = 3.0V, BATT = 1.0V
Coast Mode, OUT = 1.8V to 4.9V
Run Mode, OUT = 1.8V to 4.9V
Coast or Run Mode,
OUT = 1.8V to 4.9V
I
OUT
= 1mA to 80mA, Run Mode
BATT = 0.8V to 1.5V
OUT = 3.0V
I
OUT
= 80mA, C
OUT
= 47µF with ESR < 0.25Ω
During the inductor charge cycle
LX1
NMOS
PMOS
76
480
80
15
-3.5
-3.5
30
100
25
25
83
70
600
0.45
0.65
720
0.9
1.3
115
40
3.5
3.5
170
mA
mA
%
%
mV
mV
mV
%
mVp-p
mA
Ω
50
50
100
50
CONDITIONS
MIN
TYP
MAX
70
70
70
UNITS
ns
ns
ns
ns
ns
ns
ns
MAX847
3
_______________________________________________________________________________________
1-Cell, Step-Up
Two-Way Pager System IC
MAX847
ELECTRICAL CHARACTERISTICS (continued)
(OUT = 3.0V, BATT = 1.2V, NICD = 3.6V, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
LINEAR REGULATORS
REG1 PMOS On-Resistance
REG1 Supply Rejection (Note 15)
REG1 Clamp Voltage
REG2 Voltage Drop
REG2 Load Regulation
REG2 Supply Rejection
(Note 15)
REG3 Output Voltage
REG3 Supply Rejection (Note 15)
CONDITIONS
OUT = 3.0V, I
REG1
= 65mA
f = 268.8kHz, C
REG1
= 10µF ceramic
I
OUT
= 1mA, OUT = 4.9V
T
A
= +25°C
T
A
= -40°C to +85°C
I
REG2
= 0 to 24mA, OUT = 3.0V, R
OFS
= 15kΩ
I
REG2
= 0.1mA to 24mA
f = 268.8kHz, C
REG1
= 10µF, ceramic,
R
OFS
= 15kΩ, C
OFS
= 0.1µF, I
REG2
= 15mA
I
REG3
= 0 to 2mA
f = 268.8kHz, C
REG1
= 1µF ceramic
30
0.96
40
0.58
7.5
-50
I
OUT
= 1mA
Output = 5.5V
10mV overdrive
0.2
Measures NICD
Measures BATT
1.2
0.2
10
Measures NICD
Measures BATT
At thresholds of 200mV, 800mV, and 1270mV
At thresholds of 1200mV, 3200mV, and 5080mV
At thresholds of 200mV, 800mV, and 1270mV
-2.0
-15mV
-3.0
-60mV
-2.0
-15mV
1
4
2
8
40
10
2.0
+15mV
3.0
+60mV
2.0
+15mV
4
16
15
3.2
3.15
120
155
9
40
1.0
50
0.60
16
-3
30
1
15
0.63
30
50
400
250
50
1.27
5.08
1.27
1.04
MIN
TYP
1.5
25
3.3
3.4
3.45
190
MAX
3.1
UNITS
Ω
dB
V
mV
mV
dB
V
dB
V
mV
nA
mV
nA
µs
V
V
V
mV
mV
mV
%
%
%
mV
mV
DATA-ACQUISITION AND VOLTAGE MONITORS
LBI/RSIN Input Threshold
Falling input
LBI/RSIN Input Hysteresis
(Note 15)
LBI/RSIN Input Current
LBO/RSO Output Low
LBO/RSO Output Leakage
LBO/RSO Response Time
(Note 15)
CH0 Threshold Range (Note 15)
CH1 Threshold Range (Note 15)
CH2 Threshold Range (Note 15)
CH0 Threshold Resolution
(Note 15)
CH1 Threshold Resolution
(Note 15)
CH2 Threshold Resolution
(Note 15)
CH0 Error
CH1 Error
CH2 Error
CH0 Input Hysteresis (Note 15)
CH1 Input Hysteresis (Note 15)
4
_______________________________________________________________________________________
1-Cell, Step-Up
Two-Way Pager System IC
ELECTRICAL CHARACTERISTICS (continued)
(OUT = 3.0V, BATT = 1.2V, NICD = 3.6V, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
CH2 Input Hysteresis (Note 15)
CH0 Input Current
CH Comparator Response Time
(Note 15)
Note 1:
Note 2:
CH0 = 0.2V to 1.27V
10mV overdrive
CONDITIONS
MIN
1
-100
0.6
TYP
2
MAX
4
100
1.0
UNITS
mV
nA
µs
MAX847
Note 3:
Note 4:
Note 5:
Note 6:
Note 7:
Note 8:
Note 9:
Note 10:
Note 11:
Note 12:
Note 13:
Note 14:
Note 15:
Specifications to -40°C are guaranteed by design, not production tested.
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.
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.
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.
Current into BATT pin in addition to the supply current at OUT. This current is roughly constant from Coast to Run Mode.
Current into NICD pin when NICD isn’t being charged and isn’t regulating OUT.
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.
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.
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.
This specification is not directly tested but is guaranteed by correlation to LX on-resistance and current-limit tests.
Measured by using the internal feedback network and Coast-Mode error comparator to regulate OUT. Doesn’t include
ripple voltage due to inductor currents.
Measured by using the internal feedback network and Run-Mode error comparator to regulate OUT. Doesn’t include ripple
voltage due to inductor currents.
Uses the OUT measurement techniques described for the OUT Error, Coast Mode, and OUT Error Run Mode specifications.
PLL acquisition characteristics depend on the impedance at the FILT pin. The specification is not tested and is provided
for design guidance only.
The limits in this specification are not guaranteed and are provided for design guidance only.
__________________________________________Typical Operating Characteristics
(Circuit of Figure 2, T
A
= +25°C, unless otherwise noted.)
EFFICIENCY vs. LOAD CURRENT
(RUN MODE, V
OUT
= 3.0V)
MAX847TOC01
EFFICIENCY vs. LOAD CURRENT
(COAST MODE, V
OUT
= 3.0V)
MAX847TOC02
EFFICIENCY vs. LOAD CURRENT
(COAST MODE, V
OUT
= 2.4V)
V
IN
= 2.0V
V
IN
= 1.5V
MAX847TOC03
100
90
EFFICIENCY (%)
80
70
60
50
40
1
10
100
100
90
EFFICIENCY (%)
80
70
V
IN
= 0.8V
60
50
40
V
IN
= 1.0V
V
IN
= 2.0V
V
IN
= 1.5V
100
90
EFFICIENCY (%)
80
70
V
IN
= 1.0V
60
50
40
V
IN
= 0.8V
V
IN
= 1.2V
V
IN
= 0.8V
V
IN
= 1.0V
V
IN
= 1.2V
V
IN
= 2.0V
V
IN
= 1.5V
V
IN
= 1.2V
1000
0.1
1
10
100
1000
0.1
1
10
100
1000
LOAD CURRENT (mA)
LOAD CURRENT (mA)
LOAD CURRENT (mA)
_______________________________________________________________________________________
5
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