Lithium_Ion_Pack_Supervisor_for_3-_and_4-Cell

Features

Protects and individually moni-

tors three or four Li-Ion series
cells for overvoltage, undervolt-
age

Monitors pack for overcurrent
Designed for battery pack inte-

gration

Minimal external components
Drives external FET switches
Selectable overvoltage (V

)

thresholds

Mask-programmable by
Unitrode

Standard version4.25V

Supply current: 25µA typical
Sleep current: 0.7µA typical
16-pin 150-mil narrow SOIC

General Description

The bq2058 Lithium Ion Pack Super-
visor is designed to control the charge
and discharge cell voltages for three or
four lithium ion (Li-Ion) series cells,
accommodating battery packs contain-
ing series/parallel configurations. The
low operating current does not over-
discharge the cells during periods of
storage and does not significantly in-
crease the system discharge load. The
bq2058 can be part of a low-cost Li-Ion
charge control system within the bat-
tery pack.

The bq2058 controls two external FETs
to limit the charge and discharge poten-
tials. The bq2058 allows charging when
each individual cell voltage is below V

(overvoltage limit). If the voltage on any
cell exceeds V

for a user-configurable

delay period (t

OVD

), the

CHG pin is

driven high, shutting off charge to the
battery pack. This safety feature pre-

vents overcharge of any cell within
the battery pack. After an overvolt-
age condition occurs, each cell must
fall below V

(charge enable voltage)

for the bq2058 to re-enable charging.

The bq2058 protects batteries from
overdischarge. If the voltage on any
cell falls below V

(undervoltage

limit) for a user-configurable delay pe-
riod (t

UVD

), the DSG output is driven

high, shutting off the battery dis-
charge. This safety feature prevents
overdischarge of any cell within the
battery pack.

The bq2058 also stops discharge on
detection of an overcurrent condition,
such as a short circuit. If an overcur-
rent condition occurs for a user-
configurable delay period (t

OCD

), the

DSG output is driven high, disconnect-
ing the load from the pack. DSG re-
mains high until removal of the short
circuit or overcurrent condition.

bq2058

Lithium Ion Pack Supervisor

for 3- and 4-Cell Packs

PN205801.eps

16-Pin Narrow SOIC

DSG

NSEL

UVD

OVD

OCD

VCC

CSH

BAT1P

CHG

CTL

VSS

CSL

BAT4N

BAT3N

BAT2N

BAT1N

Pin Connections

CHG

Charge control output

CTL

Pack disable input

Low potential input

CSL

Current sense low-side
input

BAT

Battery 4 negative input

BAT

Battery 3 negative input

BAT

Battery 2 negative input

BAT

Battery 1 negative input

DSG

Discharge control output

NSEL

3- or 4-cell selection

UVD

Undervoltage delay input

OVD

Overvoltage delay input

OCD

Overcurrent delay input

High potential input

CSH

Current sense high-side
input

BAT

Battery 1 positive input

Pin Names

1/99 I

Pin Descriptions

CHG

Charge control output

This push-pull output controls the charge
path to the battery pack.

Charging is al-

lowed when low.

CTL

Pack disable input

When high, this input allows an external
source to disable the pack by making both
DSG and CHG inactive. For normal opera-
tion, the CTL pin is low.

Low potential input

CSL

Overcurrent sense low-side input

This input is connected between the low-side
discharge FET (or sense resistor) and BAT

to enable overcurrent sensing in the battery
pack's ground path.

BAT

Battery 4 negative input

This input is connected to the negative termi-
nal of the cell designated BAT4 in Figure 2.

BAT

Battery 3 negative input

This input is connected to the negative terminal
of the cell designated BAT3 in Figure 2.

BAT

Battery 2 negative input

This input is connected to the negative termi-
nal of the cell designated BAT2 in Figure 2.

BAT

Battery 1 negative input

This input is connected to the negative termi-
nal of the cell designated BAT1 in Figure 2.

This input is connected to BAT

in a three-

cell configuration.

DSG

Discharge control output

This push-pull output controls the discharge
path to the battery pack. Discharge is al-
lowed when low.

NSEL

Number of cells input

This input selects the number of series cells
in the pack. NSEL should connect to V

for

four cells and to V

for three cells.

UVD

Undervoltage delay input

This input uses an external capacitor to V

to set the undervoltage delay timing.

OVD

Overvoltage delay input

This input uses an external capacitor to V

to set the overvoltage delay timing.

OCD

Overcurrent delay input

This input uses an external capacitor to V

to set the overcurrent delay timing.

High potential input

CSH

Overcurrent sense high-side input

T h i s i n p u t i s c o n n e c t e d b e t w e e n t h e
high-side discharge FET (or sense resistor)
and BAT

to enable overcurrent sense in

the battery pack's positive supply path.

BAT

Battery 1 positive input

This input is connected to the positive terminal
of the cell designated BAT1 in Figure 2.

bq2058

Number of Cells

Configuration Pins

Battery Pins

3 cells

BAT

tied to BAT

NSEL = V

BAT

Positive terminal of first cell

BAT

Negative terminal of first cell

BAT

Negative terminal of second cell

BAT

Negative terminal of third cell

4 cells

NSEL = V

BAT

Positive terminal of first cell

BAT

Negative terminal of first cell

BAT

Negative terminal of second cell

BAT

Negative terminal of third cell

BAT

Negative terminal of fourth cell

Table 1. Pin Configuration for 3- and 4-Series Cells

bq2058

B1P

Sel1

Sel2

B1N

Sel3

Sel4

B4N

B2N

B3N

Pin 9

Pin 8

Pin 7

Pin 6

Pin 5

Sleep

Cell Inputs

NSEL

Clock

Sel4
Sel3
Sel2
Sel1

Sel3
Sel2
Sel1

Sel4

NSEL

Sleep

Pin 15

Number of Cells Select

Edge

Out

Non-Retrigger

Oneshot

Reset

Capacitor

D
CK

Reset

Overcharge

OVD

Edge

Out

Non-Retrigger

Oneshot

Reset

Capacitor

D
CK

Reset

Sleep

UVD

Edge

Out

Non-Retrigger

Oneshot

Reset

Capacitor

D
CK

Reset

OCD

Any_Above_VOV

All_Below_VCE

CTL

Pin 2

External Output Control

Pin 14

Charge Off Delay Capacitor Input

Sense High-side Input

Sense Low-side Input

70mV

Overcurrent Delay
Capacitor Input

Pin 12

Pin 5

Pin 4

Pin 9

Pin 10

Any_Below_VUV

Pin 13
Discharge Off Delay Capacitor Input

Sel4

Sel3

Sel2

Sel1

Sel4

Sel3

Sel2

Sel1

Sel4

Sel3

Sel2

Sel1

VUV

VCE

VOV

Charge Control
Output

Discharge Control
Output

Chip Negative

Supply

CHG

Overcurrent

Pin 3

Pin 1

Pin 16

CSH

B1P

B4N

CSL

Pin 5

Pin 4

Pin 9

Pin 10

CSH

B1P

B4N

CSL

DSG

160mV

Figure 1. Block Diagram

Functional Description

Figure 1 is a block diagram outlining the major compo-
nents of the bq2058. Figure 2 shows a 3- or 4-cell pack
supervisor circuit. The following sections detail the vari-
ous functional aspects of the bq2058.

Thresholds

The bq2058 monitors the lithium ion pack for the condi-
tions listed below. Shown with these conditions are the
respective thresholds used to determine if that condition
exists:

Overvoltage (V

)

Undervoltage (V

)

Overcurrent (V

OCH

, V

OCL

)

Charge Enable (V

)

Charge Detect (V

)

The bq2058 samples a cell every 40ms (typical). Every
sample is a fully differential measurement of each cell.
During this sample period, the bq2058 compares the
measurements with these thresholds to determine if any
of the these conditions exist: V

, V

, and V

Overcurrent and charge detect are conditions that are
not sampled, but are continuously monitored.

Initialization

On initial power-up, such as connecting the battery pack
for the first time to the bq2058, the bq2058 enters the
low-power sleep mode, disabling the DSG output. It is
recommended that a top to bottom cell connection
be made at pack assembly for proper initializa-
tion. A charging supply must be applied to the bq2058
circuit to enable the pack. See Low-Power Sleep Mode
and Charge Detect sections.

bq2058

POS

Si4435DY

0.1uF

Si4435DY

ZVP3306F

6.98K

* See note 1.

BAT54

* See note 2.

Notes:

1. For automatic short circuit recovery.

B1P to B1N for 3-cells.

2. Remove R11 for 4-cell. Remove R10 and connect

B1P

10K

0.001uF

CSH

VCC

BAT1P

BAT1N

BAT2N

BAT3N

BAT4N

VSS

CSL

OVD

OCD

UVD

DSG

CHG

CTL

NSEL

bq2058

R10

0 Ohm

4-Cell

0.1uF

R11

0 Ohm

3-Cell

0.01uF

0.1uF

C10

0.1uF

100K

R9
1M

2N7002

TP1

B1N

B2N

B3N

B4N

10K

0.001uF

2.7K

NEG

Figure 2. 3- or 4-Cell Li-Ion Battery Pack Supervisor

Low-Power Sleep Mode

The bq2058 enters the low-power sleep mode in two dif-
ferent ways:

On initial power-up.

After the detection of an undervoltage condi-
tionV

When the bq2058 enters the low-power sleep mode, DSG
is driven high and the device consumes 0.7

µA (typical).

The bq2058 only comes out of low-power sleep mode
when a valid charge-detect condition exists.

Charge Detect

The bq2058 continuously monitors for a charge-detect con-
dition. A valid charge-detect condition exists when either
of the conditions are true:

CSL < BAT

- 70mV (V

)

CSH > BAT

+ 70mV (V

)

A valid charge-detect enables the DSG output, allowing
charging of the lithium ion cells. This is accomplished
by applying the charging supply to the pack.

Undervoltage

Undervoltage (or overdischarge) protection is asserted
when any cell voltage drops below the V

threshold

and remains below the V

threshold for a time

exceeding a user-configurable delay (t

UVD

The DSG

output

is driven high disabling the discharge of the

pack.

The bq2058 then enters the low-power sleep

mode.

Overvoltage

Overvoltage (or overcharge) protection is asserted when
any cell voltage exceeds the V

threshold and remains

above the V

threshold for a time exceeding a user-

configurable delay (t

OVD

). The CHG pin is driven high,

disabling charge into the battery pack. Charging is dis-
abled until a valid charge enable exists. See Charge En-
able section.

Important note: If any battery pin floats (BAT

BAT

), the bq2058 assumes an overvoltage has

occurred.

Because of different manufacturers specifications for
overvoltage thresholds, the bq2058 can be available with
different V

options. Table 2 summarizes these differ-

ent voltage thresholds.

The overvoltage threshold limits are programmed
at Unitrode.

The bq2058 is the standard option

that is more readily available for sampling and
prototyping purposes.

Please contact Unitrode

for other voltage threshold and tolerance options.

Charge Enable

A valid charge enable indicates that an overvoltage
(overcharge) condition no longer exists and that the
pack is ready to accept further charge. Once overvoltage
protection is asserted, charging will not be enabled un-
til all cell voltages fall below V

. The V

threshold is

a function of V

OV,

and changes with different V

lim-

its.

= V

- 150mV

Overcurrent

The bq2058 detects an overcurrent (or short circuit) con-
dition only in the discharge direction. Overcurrent pro-
tection is asserted when either of the conditions occurs
and remain for a time exceeding a user-configurable de-
lay (t

OCD

CSL > BAT

+ V

OCL

CSH < BAT

- V

OCH

where:

OCL

= 160mV (low-side detect)

OCH

= 160mV (high-side detect)

When either of these conditions occurs, DSG is driven
high, disconnecting the load from the pack.

DSG re-

mains high until both of the voltage conditions are false,
indicating removal of the short-circuit condition.

The

user can facilitate clearing these conditions by inserting
the battery pack into a charger.

The low-side overcurrent sense can be disabled by con-
necting CSL to BAT

. This ensures that CSL is never

greater than BAT

. If low-side detection is disabled,

high-side detection must be used with CSH.

bq2058

Part No.

Limit

bq2058

4.25V

bq2058C

4.325

bq2058D

4.30V

bq2058G*

4.375V

bq2058R

4.35V

bq2058W

3.4V

Table 2. Overvoltage Threshold Options

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