SGM4056 Datasheet, PDF (12/19 Pages) SG Micro Corp – High Input Voltage Charger

SGM4056
OPERATION
Power Good Range
The power good range is defined by the following three
conditions:
1. V_IN > V_POR
2. V_IN - V_BAT > V_OS
3. V_IN < V_OVP
where the V_OS is the offset voltage for the input and
output voltage comparator, discussed shortly, and the
V_OVP is the over-voltage protection threshold given in the
Electrical Characteristics table. All V_POR, V_OS, and V_OVP
have hysteresis, as given in the Electrical Characteristics
table. The charger will not charge the battery if the input
voltage is not in the power good range.
Input and Output Comparator
The charger will not be enabled unless the input voltage
is higher than the battery voltage by an offset voltage V_OS.
The purpose of this comparator is to ensure that the
charger is turned off when the input power is removed
from the charger. Without this comparator, it is possible
that the charger will fail to power down when the input is
removed and the current can leak through the PFET pass
element to continue biasing the POR and the
Pre-Regulator blocks.
Dropout Voltage
The constant current may not be maintained due to the
R_{DS (ON)} limit at a low input voltage. The worst case R_{DS (ON)}
is at the maximum allowable operating temperature.
CHG Indication
The CHG is an open-drain output capable of sinking at
least 15mA current when the charger starts to charge,
and turns off when the EOC current is reached. The
CHG signal is interfaced either with a microprocessor
GPIO or an LED for indication.
High Input Voltage Charger
EN Input
EN is an active-low logic input to enable the charger.
Drive the EN pin to low or leave it floating to enable the
charger. This pin has a 200kΩ internal pull-down resistor
so when left floating, the input is equivalent to logic low.
Drive this pin to high to disable the charger. The
threshold for high is given in the Electrical Characteristics
table.
IREF Pin
The IREF pin has the two functions as described in the
Pin Description section. When setting the fast charge
current, the charge current is guaranteed to have 12%
accuracy with the charge current set at 500mA. When
monitoring the charge current, the accuracy of the IREF
pin voltage vs. the actual charge current has the same
accuracy as the gain from the IREF pin current to the
actual charge current.
Operation without the Battery
The SGM4056 relies on a battery for stability and works
under LDO mode if the battery is not connected. With a
battery, the charger will be stable with an output ceramic
decoupling capacitor in the range of 1µF to 200µF. In
LDO mode, its stability depends on load current, C_OUT,
etc. The maximum load current is limited by the dropout
voltage, the programmed I_REF and the thermal foldback.
Thermal Foldback
The thermal foldback function starts to reduce the charge
current when the internal temperature reaches a typical
value of 115℃.
SG Micro Corp
12
www.sg-micro.com