PS501-0901
Single Chip Field Reprogrammable Battery Manager –
Nickel Chemistries
• Single chip solution for rechargeable battery
management
• Footprint compatible with PS402
• SMBus 1.1 and SBData 1.1 compatible
• Precise capacity reporting for NiMH and NiCd
battery chemistries
• Embedded Microchip patented Accuron
®
technology contained in customizable on-chip
16-Kbyte Flash memory
• User configurable and “learned” parameters
stored in on-chip 256 x 8 EEPROM
• Algorithms and parameters fully field
reprogrammable via SMBus interface
• Integrating sigma-delta A/D converter with 9 to
16-bit programmable resolution which accurately
measures:
- Current through sense resistor
- High-voltage (18V) battery cells directly
connected to V
CELL
inputs
- Temperature measurement from on-chip
sensor or optional external thermistor
• Integrated precision silicon time base
• Twelve individually programmable input/output
pins that can be assigned as charge control I/O,
secondary safety function I/O, SOC LED output or
general purpose I/O
- Two of the twelve I/Os are high-voltage,
capable for direct drive of charge and safety
FETs
• On-chip regulator generates precision digital and
analog supply voltages directly from pack voltage
• Flexible power operating modes:
- Run: Continuous operation
- Sample: Periodic measurements at
programmable intervals
- Sleep: Shutdown mode due to low voltage;
power consumption less than 25
µA
- Shelf-Sleep: Shuts off PS501-0901 power
consumption for pack storage with automatic
wake-up on pack insertion; power
consumption is less than 1
µA
• Integrated Reset Control
- Power-on Reset
- Watchdog Timer Reset
- Brown-out Detection Reset
Pin Description
V
DDD
GPIO(4)
GPIO(5)
GPIO(6)
GPIO(7)
SMB-CLK
SMB-DTA
RSV1
RSV2
RSV3
VC(1)
V
DDA
V
SSA
RSHP
1
2
3
4
5
6
7
8
9
10
11
12
13
14
28
27
26
25
24
23
22
21
20
19
18
17
16
15
V
SSD
GPIO(3)
GPIO(2)
GPIO(1)
GPIO(0)
GPIOHV2
MCLR
GPIOHV1
GPIO(9)
GPIO(8)
R
OSC
V
REFT
V
NTC
RSHN
28-Pin SSOP Package (0.209 mil)
Pin Summary
Pin Name
V
DDD
, V
SSD
GPIO(0..9)
GPIOHV1,2
Type
Description
Supply Digital supply voltage input,
ground
I/O
I/O
Programmable digital I/O
Open-drain programmable
digital I/O for direct drive of
FETs
Master Clear; pull-up in
normal operation
SMBus interface
Pack voltage input
MCLR
SMB-CLK,
SMB-DTA
VC(1)
V
DDA
, V
SSA
I
I/O
I
Supply Voltage regulator output
(internally connected to
analog supply input); ground
I
I
O
I
I
Current sense resistor input
External thermistor input
Thermistor reference voltage
Internal oscillator bias resistor
Reserved pins
RSHP, RSHN
V
NTC
V
REFT
R
OSC
RSV1 -3
2004 Microchip Technology Inc.
PS501-0901
DS21902A-page 1
PS501-0901
1.0
PRODUCT OVERVIEW
The PS501-0901 combines a high-performance, low-
power Microchip PIC18 microcontroller core, together
with
PowerSmart
®
proprietary
monitor/control
algorithms and 3D cell models, stored in 16 Kbytes of
on-chip reprogrammable Flash memory.
Analog resources include a 16-bit sigma-delta integrat-
ing A/D and mixed signal circuitry for precision
measurement of battery current, temperature and
voltage. On-chip EEPROM is provided for storage of
user customizable and “learned” battery parameters.
An industry standard 2-wire SMBus interface supports
host communication using standard SBData
commands and status.
Additional integrated features include a high accuracy
on-chip oscillator and temperature sensor. Twelve
general purpose pins support charge or safety control
or user programmable digital I/O. Eight of them can be
used as LED drivers and two are open drain for direct
FET drive.
The PS501-0901 can be configured to accommodate
all Nickel rechargeable battery chemistries, including
NiMH and NiCd. Nickel battery packs must contain
between six and twelve series cells.
FIGURE 1-1:
PS501-0901 INTERNAL BLOCK DIAGRAM
V
DDD
V
PP
V
DDA
Digital Section
Voltage
Voltage
Reference
Reference
and
and
Tem perature
Tem perature
Sensor
Sensor
Decoder
256-byte
256-byte
EEPROM
EEPROM
16-Kbyte
16-Kbyte
FLASH
FLASH
Regulator
Regulator
V
REFT
SMB-CLK
SM B-DTA
SMBus
SM Bus
Interface
Interface
PIC18
PIC18
Microcontroller
Microcontroller
Core
Core
16-Bit
16-Bit
Sigma-Delta
Sigm a-Delta
Integrating
Integrating
A/D Converter
A/D Converter
3
VC(1)
RSV1-3
RSHP
RSHN
Analog
Analog
Input Mux
Input Mux
12
GPIO(11-0)
Program m able
Program mable
Digital
Digital
Input/Output
Input/Output
Silicon Oscillator
Silicon Oscillator
V
NTC
Analog Section
V
SSD
R
O SC
V
SSA
DS21902A-page 2
2004 Microchip Technology Inc.
PS501-0901
1.1
Architectural Description
1.5
The PS501-0901 is a a fully field reprogrammable single
chip solution for rechargeable battery management.
Figure 1-1 is an internal block diagram highlighting the
major architectural elements described below.
SMBus Interface/SBData
Commands
1.2
Microcontroller/Memory
The PS501-0901 incorporates an advanced, low-
power Microchip PIC18 8-bit RISC microcontroller
core. Memory resources include 16 Kbytes of repro-
grammable Flash memory for program/data storage
and 256 bytes of EEPROM for parameter storage. Both
memory arrays may be reprogrammed through the
SMBus interface.
Communication with the host is fully compliant with the
industry standard Smart Battery System (SBS)
specification. Included is an advanced SMBus
communications engine that is compliant with the
SMBus v1.1 protocols. The integrated firmware
processes all the revised Smart Battery Data (SBData)
v1.1 values.
1.6
Accurate Integrated Time Base
The PS501-0901 provides a highly accurate RC
oscillator that provides accurate timing for self-
discharge and capacity calculations and eliminates the
need for an external crystal.
1.3
A/D Converter
1.7
Temperature Sensing
An integrated temperature sensor is provided to
minimize component count when the PS501-0901 IC is
located in close physical proximity to the battery cells
being monitored. As an option, a connection is
provided for an external thermistor that can also be
monitored.
The PS501-0901 performs precise measurements of
current, voltage and temperature, using a highly
accurate 16-bit integrating sigma-delta A/D converter.
The A/D can be calibrated to eliminate gain and offset
errors and incorporates an auto-zero offset correction
feature that can be performed while in the end system
application.
1.4
Microchip Firmware/Battery Models
1.8
General Purpose I/O
Contained within the 16-Kbyte Flash memory is the
Microchip developed battery management firmware
that incorporates proprietary algorithms and sophisti-
cated 3-dimensional cell models. Developed by battery
chemists, the patented, self-learning 3D cell models
contain over 250 parameters and compensate for self-
discharge, temperature and other factors. In addition,
multiple capacity correction and error reducing
functions are performed during charge/discharge
cycles to enhance accuracy and improve fuel gauge
and charge control performance. As a result, accurate
battery capacity reporting and run-time predictions with
less than 1% error are achievable.
The reprogrammability of the Flash allows firmware
upgrades and customized versions to be rapidly
created without the need for silicon revisions.
The PS501-0901 can be easily customized for a
particular application’s battery cell chemistry. Standard
configuration files are provided by Microchip for a wide
variety of popular rechargeable cells and battery pack
configurations.
Twelve programmable digital input/output pins are
provided by the PS501-0901. Eight of these pins can
be used as LED outputs to display State-Of-Charge
(SOC) or for direct control of external charge circuitry.
Alternatively, they can be used as general purpose
input/outputs. Two of the I/Os are open-drain outputs
and can thus be used to directly drive FETs or other
high-voltage applications.
2004 Microchip Technology Inc.
DS21902A-page 3
PS501-0901
TABLE 1-1:
Pin
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
PIN DESCRIPTIONS
Name
V
DDD
GPIO(4)
GPIO(5)
GPIO(6)
GPIO(7)
SMB-CLK
SMB-DTA
RSV1
RSV2
RSV3
VC(1)
V
DDA
V
SSA
RSHP
RSHN
V
NTC
Description
(Input) Filter capacitor input for digital supply voltage.
(Bidirectional) Programmable general purpose digital input/output pin (4) or LED driver.
(Bidirectional) Programmable general purpose digital input/output pin (5) or LED driver.
(Bidirectional) Programmable general purpose digital input/output pin (6) or LED driver.
(Bidirectional) Programmable general purpose digital input/output pin (7) or LED driver.
SMBus clock pin connection.
SMBus data pin connection.
Reserved – Must be connected to ground.
Reserved – Must be connected to ground.
Reserved – Must be connected to ground.
(Input) Pack voltage input.
(Input) Analog supply voltage input.
Analog ground reference point.
(Input) Current measurement A/D input from positive side of the current sense resistor.
(Input) Current measurement A/D input from negative side of the current sense resistor.
(Input) A/D input for use with an external temperature circuit. This is the midpoint
connection of a voltage divider where the upper leg is a thermistor (103ETB type) and
the lower leg is a 3.65 kOhm resistor. This input should not go above 150 mV.
(Output) Reference voltage output for use with temperature measuring A/D circuit. This
150 mV output is the top leg of the voltage divider and connects to an external
thermistor.
External bias resistor.
(Bidirectional) Programmable general purpose digital input/output pin (8).
(Bidirectional) Programmable general purpose digital input/output pin (9).
(Bidirectional) Programmable general purpose digital input/output pin (10).
Open-drain, high-voltage tolerant.
(Input) Master Clear. Must be pulled up for normal operation.
(Bidirectional) Programmable general purpose digital input/output pin (11).
Open-drain, high-voltage tolerant.
(Bidirectional) Programmable general purpose digital input/output pin (0) or LED driver.
(Bidirectional) Programmable general purpose digital input/output pin (1) or LED driver.
(Bidirectional) Programmable general purpose digital input/output pin (2) or LED driver.
(Bidirectional) Programmable general purpose digital input/output pin (3) or LED driver.
Digital ground reference point.
17
V
REFT
18
19
20
21
22
23
24
25
26
27
28
R
OSC
GPIO(8)
GPIO(9)
GPIOHV1
MCLR
GPIOHV2
GPIO(0)
GPIO(1)
GPIO(2)
GPIO(3)
V
SSD
DS21902A-page 4
2004 Microchip Technology Inc.
PS501-0901
2.0
A/D OPERATION
The PS501-0901 A/D converter measures voltage,
current and temperature and integrates the current
over time to measure State-Of-Charge. The voltage of
the entire pack is monitored and the pack is calibrated
for accuracy. Using an external sense resistor, current
is monitored during both charge and discharge and is
integrated over time using the on-chip oscillator as the
time base. Temperature is measured from the on-chip
temperature sensor or an optional external thermistor.
Current and temperature are also calibrated for
accuracy.
The equation for current measurement resolution and
sense resistor selection is shown in the following
equation.
EQUATION 2-1:
9.15 mV/R
SENSE
(milliohms) = Current LSB
(Minimum current measurement if >
NullCurr)
Current LSB x 16384 = Maximum Current
Measurement Possible
In-circuit calibration of the current is done using the
SMBus interface at time of manufacture to obtain
absolute accuracy. The current measurement equation
is:
2.1
A/D Converter List
The A/D converter alternately measures pack voltage,
current, temperature and auto-offset as explained
below. The schedule for the sequence and frequency of
these measurements is programmable, as is the num-
ber of bits used. The default scheduling uses four lists.
At near full (above the voltage point
ADLNearFull)
and
near empty (below the voltage point
ADLNearEmpty),
voltage intensive lists are used to accurately end
charge or discharge. In between
ADLNearFull
and
ADLNearEmpty,
a current intensive schedule is used
to more accurately calculate capacity.
EQUATION 2-2:
I(ma) = (I_A/D –
COCurr
–
COD)
*
CFCurr/16384
where:
I_A/D
is the internal measurement
COCurr
is the “Correction Offset for Current” which com-
pensates for any offset error in current measurement
stored in EEPROM.
CFCurr
is the “Correction Factor for Current”, which
compensates for any variances in the actual sense
resistance over varying currents stored in EEPROM.
Figure 2-1 shows the relationship of the
COCurr
and
CFCurr
values.
2.2
Current Measurement
The A/D input channels for current measurement are
the RSHP and RSHN pins. The current is measured
using an integrating method, which averages over time
to get the current measurement and integrates over
time to get a precise measurement value.
A 5 to 600 milliohm sense resistor is connected to
RSHP and RSHN in a typical application schematic.
The maximum input voltage at either RSHP or RSHN is
+/-150 mV. The sense resistor should be properly sized
to accommodate the lowest and highest expected
charge and discharge currents, including suspend and/
or standby currents.
Circuit traces from the sense resistor should be as
short as practical without significant crossovers or
feedthroughs. Failure to use a single ground reference
point at the negative side of the sense resistor can
significantly degrade current measurement accuracy.
The EEPROM value,
NullCurr,
represents the zero
zone current of the battery. This is provided as a
calibration guardband for reading zero current.
Currents below the +/-
NullCurr
(in mA) limit are read
as zero and are not included in the capacity algorithm
calculations. A typical value for
NullCurr
is 3 mA, so
currents between -3 mA and +3 mA will be reported as
zero and not included in the capacity calculations.
FIGURE 2-1:
COCurr AND CFCurr
VALUE RELATIONSHIP
Raw Measurement
Ideal A/D Response
Actual A/D
Response
COCurr
CFCurr
Actual Current
2004 Microchip Technology Inc.
DS21902A-page 5
