RT9516 RICHTEK [Richtek Technology Corporation], RT9516 Datasheet - Page 8

• Manufacturer Part Number: RT9516
• Description: Linear Single Cell Li-lon Battery Charger with Single Input Supply for Portable Applications
• Manufacturer: RICHTEK [Richtek Technology Corporation]

RT9516
Applications Information
The RT9516 is a fully integrated low cost single-cell
Li-Ion battery charger with a constant current (CC mode)
or a constant voltage (CV mode). The CC mode current is
set with the external resistor R
is fixed at 4.2V. If the battery voltage is below a typical
2.5V pre-charge threshold, the RT9516 charges the
battery with a trickle current until the battery voltage rises
above the pre-charge threshold. The RT9516 is capable
of being powered up from AC adapter and USB (Universal
Serial Bus) port inputs.
ACIN Over-Voltage Protection
The input voltage is monitored by the internal comparator.
The OVP threshold is set at 7V (typ.). When the input
voltage exceeds the threshold, the controller outputs a
logic signal to turn off the power P-MOSFET to prevent
the high input voltage from damaging the electronics in
the handheld system. However, AC input voltage over 28V
still leads the RT9516 to damage. When the input
overvoltage condition is removed, the controller will enables
the output by running through the soft-start.
Charger Enable 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.
Battery Charge Profile
The RT9516 charges a Li-ion battery with a constant
current (CC) or a constant voltage (CV). The constant
current of ISET is set with the external resistor R
the constant voltage is fixed at 4.2V. If the battery voltage
is below a typical 2.5V trickle-charge threshold, the RT9516
charges the battery with a trickle current until the battery
voltage rises above the trickle charge threshold. When
the battery voltage reaches 4.2V, the charger enters a
CV mode and regulates the battery voltage at 4.2V to
fully charge the battery without the risk of over charge.
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8
SET
and the CV mode voltage
SET
and
a. Battery Pre-Charge Current
During a charge cycle, if the battery voltage is below the
pre-charge threshold, the RT9516 applies a pre-charge
mode to the battery. This feature revives deeply discharged
cells and protects battery life. The internally determined
pre-charge rate of the RT9516 is 10% of the constant
charge current.
b. Battery Fast-Charge Current
The RT9516 offers ISET pin to determine the charge
current. By an external resistor connected between the
ISET and GND. The charge current can be calculated by
the following equation :
K
I
charge
SET
1200
1000
= 1140; V
800
600
400
200
=
0
10%
Programmed
Charge
Current
Programmed
Pre-Charge
K
1
Mode
SET
Current
Charge
2
I
ISET
R
SET
V
3
SET
SET
Charge Current vs. R
Current Mode
= 1.4(typ.)
4
Constant
Precharge
Threshold
2.5V
5
Figure 1
Figure 2
6
Voltage Mode
7
R
Constant
4.2V
Battery
Regulation
Voltage
threshold
SET
8
DS9516-01 April 2011
(kΩ)
9 10 11 12 13 14
SET
Recharge
Phase
Time