LTC4012IUF#PBF Linear Technology, LTC4012IUF#PBF Datasheet - Page 14

• Manufacturer Part Number: LTC4012IUF#PBF
• Description: IC BATT CHRGR MC HI-EFF 20-QFN
• Manufacturer: Linear Technology

Specifications of LTC4012IUF#PBF

• Function: Charge Management
• Battery Type: Multi-Chemistry
• Voltage - Supply: 6 V ~ 28 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 20-WFQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

LTC4012/
LTC4012-1/LTC4012-2
operation
Adapter Input Current Limit
The LTC4012 can monitor and limit current from the input
DC supply, which is normally an AC adapter. When the
programmed adapter input current is reached, charge
current is reduced to maintain the desired maximum input
current. The ITH and PROG pins will reflect the reduced
charge current. This limit function avoids overloading the
DC input source, allowing the product to operate at the
same time the battery is charging without complex load
management algorithms. The battery will automatically be
charged at the maximum possible rate that the adapter will
support, given the application’s operating condition. The
LTC4012 can only limit input current by reducing charge
current, and in this case the charger uses nonsynchro-
nous PWM operation to prevent boosting if the average
charge current falls below about 25% of the maximum
programmed current. Note that the ICL indicator output
becomes active (low) at an adapter input current level just
slightly less than that required for the internal amplifier to
begin to assert control over the PWM loop.
Charger Status Indicator Outputs
The LTC4012 open-drain indicator outputs provide valu-
able information about the IC’s operating state and can
be used for a variety of purposes in applications. Table 1
summarizes the state of the three indicator outputs as a
function of LTC4012 operation.

BOTTOM FET
TOP FET
INDUCTOR
CURRENT
OFF
OFF
ON
ON
Figure 2. PWM Waveforms
t
OFF
Table 1. LTC4012 Open-Drain Indicator Outputs
PWM Controller
The LTC4012 uses a synchronous step-down architec-
ture to produce high operating efficiency. The nominal
operating frequency of 550kHz allows use of small filter
components. The following conceptual discussion of basic
PWM operation references Figure 1.
The voltage across the external charge current sense
resistor R
instantaneous current (V
where it is averaged by an external capacitor and converted
to a voltage by the programming resistor R
PROG and GND. The PROG voltage becomes the aver-
age charge current input signal to error amplifier EA. EA
also receives loop control information from the battery
voltage feedback input V
limit circuit.
ACP
Off
On
On
On
On
On
Off
SENSE
CHRG
On or
25µA
25µA
25µA
Off
Off
On
On
is measured by current amplifier CA. This
On or
ICL
Off
Off
Off
Off
On
On
Off
SENSE
FB
and the adapter input current
CHARGER STATE
No DC Input (Shutdown)
Shutdown or Reverse Current
Bulk Charge
Low Current Charge or Initial
DCIN – BAT <500mV
Input Current Limit During Bulk
Charge
Input Current Limit During Low
Current Charge
Indicated Charge with DCIN - BAT
< 300mV. Bulk charge may be less
than programmed value.
/R
IN
) is fed to the PROG pin
THRESHOLD
SET BY ITH
VOLTAGE
4012 F02
PROG
between
4012fa