Dual Mobile-Friendly PWM Controller with
DDR Memory Option
The ISL6225 dual PWM controller delivers high efficiency and
tight regulation from two voltage regulating synchronous buck
DC/DC converters. The ISL6225 PWM power supply controller
was designed especially for DDR DRAM, SDRAM, and graphic
chipset applications in high performance desknote PCs,
notebook PCs, sub-notebook PCs, and PDAs.
Automatic mode selection of constant-frequency synchronous
rectification at heavy load, and hysteretic diode-emulation at
light load, assure high efficiency over a wide range of
conditions. The hysteretic mode of operation can be disabled
separately on each PWM converter if constant-frequency
continuous-conduction operation is desired for all load levels.
Efficiency is further enhanced by using the lower MOSFET
RDS(ON) as the current sense element.
Voltage-feed-forward ramp modulation, average current mode
control, and internal feedback compensation provide fast
response to input voltage and output load transients. Input
current ripple is minimized by channel to channel PWM
phase shift of 0°, 90°, or 180° determined by input voltage
and status of the DDR pin.
The ISL6225 can control two independent output voltages
adjustable from 0.9V to 5.5V or, by activating the DDR pin,
transform into a complete DDR memory power supply
solution. In DDR mode, CH2 output voltage VTT tracks CH1
output voltage VDDQ. CH2 output can both source and sink
current, an essential power supply feature for DDR memory
systems. The reference voltage VREF required by DDR
memory is generated as well.
In dual power supply applications the ISL6225 monitors the
output voltage of both CH1 and CH2. An independent
PGOOD (power good) signal is asserted for each channel
after the soft-start sequence has completed, and the output
voltage is within ±10% of the set point. In DDR mode CH1
generates the only PGOOD signal.
Built-in over-voltage protection prevents the output from
going above 115% of the set point by holding the lower
MOSFET on and the upper MOSFET off. When the output
voltage decays below the over-voltage threshold, normal
operation automatically resumes. Once the soft-start
sequence has completed, under-voltage protection may
latch the ISL6225 off if either output drops below 75% of its
set point value.
Adjustable over-current protection (OCP) monitors the
voltage drop across the RDS(ON) of the lower MOSFET. If
more precise current-sensing is required, an external current
sense resistor may be used.
PART NUMBER TEMP. (oC) PACKAGE
-10 to 85
28 Ld SSOP
-10 to 85 28 Ld SSOP Tape
• Provides regulated output voltage in the range of 0.9V-5.5V
- High efficiency over wide load range
- Synchronous buck converter with hysteretic operation at
- Inhibit Hysteretic mode on one, or both channels
• Complete DDR memory power solution
- VTT tracks VDDQ/2
- VDDQ/2 buffered reference output
• No current-sense resistor required
- Uses MOSFET RDS(ON)
- Optional current-sense resistor for precision Over-Current
• Under-voltage lock-out on VCC pin
• Dual input voltage mode operation
- Operates directly from battery 5V to 24V input
- Operates from 3.3V or 5V system rail
- VCC from 5V only
• Excellent dynamic response
- Combined voltage feed-forward and average current
• Power-good signal for each channel
• 300kHz switching frequency
- 180° channel to channel phase operation for reduced input
ripple when not in DDR mode
- 0° channel to channel phase operation in DDR mode for
reduced channel interference
- 90° channel to channel phase operation for reduced input
ripple in DDR mode when VIN is at GND.
• Mobile PCs
• Hand-held portable instruments
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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