DS2790 Maxim Integrated Products, DS2790 Datasheet - Page 36

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

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COCF
DOCF
SCF
OVF
UVF
Reserved
CC
DC
Reserved
CE
DE
PMM
Protection Register
The Protection Register allows system software to determine if a protection fault condition has occurred and what
triggered the protection fault. When a protection fault occurs, its corresponding protection flag is set. The flag will
remain set until system software clears the bit after the fault is no longer present. System software can also disable
charging or discharging by clearing the charge enable or discharge enable bits, or system software can completely
disable the ADC and/or the protection FETs using the PMM bits. There is no way for system software to override a
fault condition and enable the FETs.
Figure 19. Protection Register Format (PROT)
Adjusting Protection Thresholds
The protection thresholds are set in two locations. The Charge Overcurrent threshold, Discharge Overcurrent
threshold, Short-Circuit Current threshold, and Short-Circuit Delay thresholds are set in the ADC Configuration
Register location 600Ah. Values for Overvoltage, Undervoltage, and all temperature thresholds are stored in the
password protected memory. See the Password Protected User Trim section.
High Side N-Channel Protection FETs
The DS2790 controls charging and discharging through external high-side N-FETs controlled through the CC and
DC pins. An internal charge pump generates the voltage needed to drive the external FETs. An external capacitor
connected between the CP and VSS pins stores the charge needed for the DS2790 to maintain the CC and DC
outputs. To disable discharging, the DS2790 internally connects DC to V
internally connects CC to V
V
when selecting external FETs:
OCP
FIELD
4
by internally pulling CC and DC up to the CP voltage. The system designer should consider the following
BIT
7:4
1:0
15
14
13
12
11
10
9
8
3
2
DD
. To enable charging or discharging, the DS2790 drives the appropriate FET gate to
Read Only
Read Only
Read Only
Read Only
FORMAT
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Charge Overcurrent Flag. Set to 1 by an COC fault condition.
Can only be reset by system software after fault is corrected.
Discharge Overcurrent Flag. Set to 1 by a DOC fault condition.
Can only be reset by system software after fault is corrected.
Short Circuit Flag. Set to 1 by a SC fault condition. Can only be
reset by system software after fault is corrected.
Overvoltage Flag. Set to 1 by an OV fault condition. Can only be
reset by system software after fault is corrected.
Undervoltage Flag. Set to 1 by a UV fault condition. Can only be
reset by system software after fault is corrected.
Undefined
CC Pin Mirror. This bit mirrors the state of the CC pin.
DC Pin Mirror. This bit mirrors the state of the DC pin.
Undefined
Charge Enable.
0 = Charge FET is disabled.
1 = Charge FET is enabled unless disabled by fault.
Writing this bit to 1 will not override a fault condition.
Discharge Enable.
0 = Discharge FET is disabled.
1 = Discharge FET is enabled unless disabled by fault.
Writing this bit to 1 will not override a fault condition.
Protection and Measurement Modes.
0 0 = ADC disabled, CC and DC low.
0 1 = ADC enabled, CC and DC low.
1 0 = ADC enabled, CC and DC low.
1 1 = ADC enabled, CC and DC high.
DS2790 Programmable 1-Cell Li-Ion Fuel Gauge and Protector
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DEFINITION
SS
. To disable charging, the DS2790