ia3513 integration, ia3513 Datasheet - Page 12

• Manufacturer Part Number: ia3513
• Description: Headset Voice And Power Solution
• Manufacturer: integration

Operation in PWM Mode
In normal operation, the feedback voltage is scaled and the reference voltages subtracted to create an error signal. This error
signal is digitized by a simple continuous-time sigma delta modulator. The resulting bit stream is processed by the digital
compensator and the digital output word is presented to the pulse width modulator. The pulse width modulator switches the
supply switch and synchronous rectifier at the switching frequency with an adjustable duty cycle control which is controlled by
the PWM input word. The digital compensator determines the correct duty cycle to provide for the correct output voltage while
ensuring stability.
The PWM mode operation can be forced by the host using two mechanisms.
Forced PWM
When bit 6 (FPWM) of register 25 is set , the DC-DC will operate always in PWM mode.
Forced PWM by Clock Request
When the bit 5 (CPWM) of register 25 is set the DC-DC will operate in forced PWM when the Clk26Rqst pin is high.
This guarantees that the DC-DC is running in PWM mode when the RF device is operating.
The default setting is FPWM=0 and CPWM=1, the DC-DC is by default in Forced PWM by Clock Request mode.
Operation in Pulse-Skipping Mode
The DC-DC can operate in a low power pulse skipping mode. In this mode, the synchronous rectifier current is sensed and when
the synchronous rectifier current is sufficiently negative and the output voltage is on spec, the voltage mode control loop, PWM,
and oscillator are shutdown. Everything is re-enabled when the output voltage drops below the error threshold. Then the system
is re-enabled without soft-start.
Start Up and PowerDown
The DC-DC is automatically powered up without any intervention from the host, as the host can not operate without the DC-DC
output voltage.
The DC-DC power up is triggered by one of the following events:
-Charger insertion when the IA3513 is in sleep mode
-On button push event when the IA3513 is in sleep mode.
To shutdown the DC-DC the bit 7 of register 25 must be cleared. When this is done the DC-DC is shut down and the IA3513
enters sleep mode powering down all blocks, but still being able to start a charge or detect the on button push.
Passive Network Selection
To allow for a fixed internal compensator, the external inductor and capacitor need to be specified and are not allowed to be
chosen by the user of the regulator. The following table provides the only acceptable inductor and capacitor options:
Frequency = 1024 kHz
Component
Capacitor
Inductor
Value
10 µ H
10 µ F
Recommended
Maximum ESR
200 m Ω
50 m Ω
Tolerance
20 %
20 %
IA3513
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