DS2790 Maxim Integrated Products, DS2790 Datasheet - Page 34

• Manufacturer Part Number: DS2790
• Description: Programmable 1-Cell Li-Ion Fuel Gauge and Protector
• Manufacturer: Maxim Integrated Products

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LITHIUM-ION PROTECTION
For safety, lithium-Ion cell protection functions are handled by a completely independent state machine. Application
firmware can disable the protection FETs, but is not able to override the protector and enable the FETs. During
active operation (CPU or Analog mode), the DS2790 constantly monitors cell voltage and current to protect the
battery from overcharge (overvoltage), overdischarge (undervoltage), excessive charge and discharge currents
(overcurrent, short circuit), and extreme temperatures (overtemperature, undertemperature). Protection conditions
and DS2790 responses are described in the following sections and summarized in Table 13 and Figure 18.
Table 13. Lithium-Ion Protection Conditions and DS2790 Responses
V
Under-/Overtemp conditions have no activation delay from the time the Temperature register updates. The temperature register result is an
average over 220ms, this provides protection against the MOSFETs oscillating.
Overvoltage, OV. If the cell voltage on V
overvoltage delay, t
register. When the cell voltage falls below charge enable threshold V
(unless another protection condition prevents it). Discharging remains enabled during overvoltage, and the DS2790
re-enables the charge FET before V
Undervoltage, UV. If the voltage of the cell drops below undervoltage threshold, V
undervoltage delay, t
protection register. The DS2790 provides a current-limited (I
charge severely depleted cells. The recovery path is enabled when 0 £ V
DS2790 returns to normal operation.
Charge Overcurrent, COC. The voltage difference between the IS1 pin and the IS2 pin (V
filtered voltage drop across the current-sense resistor. If V
than overcurrent delay t
register. The charge current path is not re-established until the voltage on the PLS pin drops below V
DS2790 provides a test current of value I
offending charge current source. The Charge V
Configuration register.
Overcurrent, Discharge
Short Circuit
Charge Overtemperature
Charge Undertemperature
Discharge Overtemperature
Discharge Undertemperature
Overvoltage
Undervoltage
Overcurrent, Charge
IS
Note 1:
Note 2:
Note 3:
Note 4:
4
= V
IS1
- V
CONDITION
IS2
If V
With test current I
With test current I
Temperature faults must be enabled through the TLIME bit in password protected trim memory. Temperature fault thresholds are
determined by the state of TLIM[1:0]. See Password Protected User Trim.
. Off = V
IN
<
V
PLS
UV
, release is delayed until the recovery charge current (I
OVD
for CC and V
UVD
, the DS2790 shuts off the external charge FET and sets the OVF bit in the protection
OCD
, the DS2790 shuts off the charge and discharge FETs and sets the UVF bit in the
TST
TST
, the DS2790 shuts off both external FETs and sets the COCF bit in the protection
flowing from PLS to V
flowing from V
THRESHOLD
DD
T
T
T
T
V
V
V
V
V
for DC.
A
A
A
A
IS
IN
IN
IS
IS
> T
> T
≤ T
≤ T
IN
< -V
> V
< V
> V
> V
< V
CH
CL
DH
DL
.
OC
OV
UV
SC
OC
All voltages are with respect to V
DD
(4)
(4)
(4)
(4)
CE
to PLS (pullup on PLS).
TST
if a discharge current of V
IN
SS
exceeds the overvoltage threshold, V
from PLS to V
(pulldown on PLS).
OC
ACTIVATION
DS2790 Programmable 1-Cell Li-Ion Fuel Gauge and Protector
DELAY
34 of 41
limit is programmable through the COCT bits in the ADC
t
t
t
t
t
OCD
OCD
OVD
UVD
SCD
IS
exceeds overcurrent threshold V
RC
SS
RC
) recovery charge path from PLS to V
) charges the battery and allows V
SS
to pull PLS down to detect the removal of the
. I
CC Low, DC Low
CC Low, DC Low
SNS
IS
RESPONSE
CE
≤ -2mV is detected.
references current delivered from pin SNS.
CC Low
DC Low
DC Low
CC Low
CC Low
DC Low
DC Low
, the DS2790 re-enables the charge FET
IN
< V
CE
OV
. Once V
UV
, for a period longer than
, for a period longer than
RELEASE THRESHOLD
V
(charger connected)
V
V
V
IN
PLS
OC
IS
PLS
PLS
PLS
to exceed
V
IN
= V
V
> V
T
T
T
T
for a period longer
IN
< V
> V
> V
IS
A
A
A
A
exceeds V
< V
≤ T
> T
≤ T
> T
≤ -2mV
IN
IS1
DD
DD
DD
+ 0.15V
CE
CH
DH
CL
DL
DD
- V
V
- V
- V
- V
DD
, or
(4)
(4)
UV
(4)
(4)
- V
TP
TP
TP
IS2
.
to gently
(2)
(3)
(3)
) is the
TP
(1)
UV
. The
the