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RC5053
PRODUCT SPECIFICATION
8
P
Notes:
1. These code selections are disabled in RC5053
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
Disabled
1
(1.65)
Disabled
1
(1.70)
Disabled
1
(1.75)
1.80
1.85
1.90
1.95
2.00
2.05
SHDN
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
3.0
3.1
3.2
3.3
3.4
3.5
Table 3. Rated Output Voltage
(continued)
Input Pin
V
ID2
Rated Output
Voltage (V)
V
ID4
V
ID3
V
ID1
V
ID0
Applications Information
Overview
The RC5053 is a voltage feedback, synchronous switching
regulator controller (see Block Diagram) designed for use in
high power, low voltage step-down (buck) converters. It is
designed to satisfy the requirements of the Intel Pentium II
power supply specification. It includes an on-chip DAC to
control the output voltage, a PWM generator, a precision ref-
erence trimmed to
±
1%, two high power MOSFET gate driv-
ers and all the necessary feedback and control circuitry to
form a complete switching regulator circuit.
The RC5053 includes a current limit sensing circuit that uses
the upper external power MOSFET as a current sensing ele-
ment, eliminating the need for an external sense resistor.
Once the current comparator, CC, detects an overcurrent con-
dition, the duty cycle is reduced by discharging the soft start
capacitor through a voltage-controlled current source. Under
severe overloads or output short circuit conditions, the chip
will be repeatedly forced into soft start until the short is
removed, preventing the external components from being
damaged. Under output over-voltage conditions, the
MOSFET drivers will be disabled permanently until the chip
power supply is recycled or the OUTEN pin is toggled.
OUTEN can optionally be connected to an external negative
temperature coefficient (NTC) thermistor placed near the
external MOSFETs or the microprocessor. Three threshold
levels are provided internally. When OUTEN drops to 2V, OT
will trip, issuing a warning to the external CPU. If the tem-
perature continues to rise and the OUTEN input drops to
1.7V, the G1 and G2 pins will be forced low. If OUTEN is
pulled below 1.2V, the RC5053 will go into shutdown mode,
cutting the supply current to a minimum. If thermal shutdown
is not required, OUTEN can be connected to a conventional
TTL enable signal. The free-running 300kHz PWM
frequency can be synchronized to a faster external clock