Product Specification
IXD3235/36/37
BLOCK DIAGRAMS
IXD3235/36/37 A Series
IXD3235/36/37 B/C/E/G Series
IXD3235/36/37 D/F Series
Internal diodes include an ESD protection and a parasitic diode
BASIC OPERATION
The IXD3235/36/37 series consists of a Reference Voltage source, Ramp Wave Generator, Error Amplifier, PWM
Comparator, Phase Compensation circuit, output voltage resistive divider, P-channel switching transistor, N-
channel transistor for the synchronous switch, Current Limiter circuit, UVLO circuit, and others. (See the block
diagram above.)
The Error Amplifier compares output voltage divided by internal (external for D/F versions) resistors RFB1/RFB2 with
the internal reference voltage. Amplified difference between these two signals applies to the one input of the PWM
Comparator, while ramp voltage from the Ramp Wave Generator applies to the second input. Resulting PWM pulse
determines switching transistor ON time. It goes through the Buffer and it appears at the gate of the internal P-
channel switching transistor. This continuous process stabilizes output voltage.
The Current Feedback circuit monitors current of the P-channel transistor at each switching cycle, and modulates
output signal from the Error Amplifier to provide additional feedback. This guarantees a stable converter operation
even with low ESR ceramic load capacitor.
Reference Voltage Source
The Reference Voltage Source provides the reference voltage to ensure stable output voltage of the DC/DC
converter.
Ramp Wave Generator
The Ramp Wave Generator produces ramp waveform signal needed for PWM operation, and signals to
synchronize all the internal circuits. It operates at internally fixed 1.2 MHz or 3.0 MHz frequency.
PS034201-0515
PRELIMINARY
9
ZILOG [ ZILOG, INC. ]
