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www.fairchildsemi.com
Pentium is a registered trademark of Intel Corporation
Rev. 1.2.0
Features
Programmable output from 1.3V to 3.5V using an
integrated 5-bit DAC
Remote sense
Active Droop
85% efficiency typical at full load
Integrated Power Good and Enable/Soft Start functions
Drives N-channel MOSFETs
Overcurrent protection using MOSFET sensing
16 pin SOIC package
Meets Intel Pentium II & III specifications using
minimum number of external components
Applications
Power supply for Pentium
II & III
VRM for Pentium II & III processor
Telecom line cards
Routers, switches & hubs
Programmable step-down power supply
Description
The RC5057 is a synchronous mode DC-DC controller IC
which provides a highly accurate, programmable output voltage
for all Pentium II & III CPU applications and other high-perfor-
mance processors. The RC5057 features remote voltage
sensing, adjustable current limit, and active droop for optimal
converter transient response. The RC5057 uses a 5-bit D/A
converter to program the output voltage from 1.3V to 3.5V.
The RC5057 uses a high level of integration to deliver load cur-
rents in excess of 16A from a 5V source with minimal exter-
nal circuitry. Synchronous-mode operation offers optimum
efficiency over the entire specified output voltage range. An
on-board precision low TC reference achieves tight tolerance
voltage regulation without expensive external components,
while active droop permits exact tailoring of voltage for the
most demanding load transients. The RC5057 also offers
integrated functions including Power Good, Output Enable/
Soft Start and current limiting, and is available in a 16 pin
SOIC package.
Block Diagram
1
VID0
GNDP
7
6
10
3
8
9
2
-
+
-
+
OSC
1.24V
Reference
Digital
Control
5-Bit
DAC
VID1
VID2
VID3
VID4
16 15141312
+5V
+12V
PWRGD
-
+
ENABLE/SS
VO
GNDA
11
LODRV
HIDRV
VCCP
R
S
5
VCCA
+5V
4
+
-
Power
Good
RC5057
High Performance Programmable Synchronous
DC-DC Controller for Low Voltage Microprocessors
RC5057
PRODUCT SPECIFICATION
2
REV. 1.2.0 2/10/00
Pin Assignments
Pin Definitions
Pin Number
Pin Name
Pin Function Description
1
ENABLE/SS
Output Enable/Softstart.
A logic LOW on this pin will disable the output. An
internal current source allows for open collector control. This pin also doubles as
soft start.
2
PWRGD
Power Good Flag.
An open collector output that will be logic LOW if the output
voltage is not within 12% of the nominal output voltage setpoint.
3
IFB
Current Feedback.
Pin 3 is used in conjunction with pin 10, as the input for the
current feedback control loop. Layout of these traces is critical to system
performance. See Application Information for details.
4
VFB
Voltage Feedback.
Pin 4 is used as the input for the voltage feedback control
loop. See Application Information for details regarding correct layout.
5
VCCA
Analog VCC.
Connect to system 5V supply and decouple with a 0.1F ceramic
capacitor.
6
GNDP
Power Ground.
Return pin for high currents flowing in pin 8 (VCCP). Connect to
a low impedance ground.
7
LODRV
Low Side FET Driver.
Connect this pin to the gate of an N-channel MOSFET for
synchronous operation. The trace from this pin to the MOSFET gate should be
<0.5".
8
VCCP
Power VCC.
For both high side and low side FET drivers. Connect to system 12V
supply, and decouple with a 4.7F tantalum and a 0.1F ceramic capacitor.
9
HIDRV
High Side FET Driver.
Connect this pin to the gate of an N-channel MOSFET.
The trace from this pin to the MOSFET gate should be <0.5".
10
SW
High side driver source and low side driver drain switching node.
Together
with IFB pin allows FET sensing for current.
11
GNDA
Analog Ground.
Return path for low power analog circuitry. This pin should be
connected to a low impedance system ground plane to minimize ground loops.
1216
VID0-4
Voltage Identification Code Inputs.
These open collector/TTL compatible inputs
will program the output voltage over the ranges specified in Table 2. Pull-up
resistors are internal to the controller.
1
2
3
4
5
6
7
8
9
1 0
1 1
1 2
1 6
1 5
1 4
1 3
RC5057
ENABLE/SS
PWRGD
IFB
VFB
VCCA
GNDP
LODRV
VCCP
VID0
VID1
VID2
VID3
VID4
GNDA
SW
HIDRV
PRODUCT SPECIFICATION
RC5057
REV. 1.2.0 2/10/00
3
Absolute Maximum Ratings
Recommended Operating Conditions
Supply Voltage VCCA to GND
13.5V
Supply Voltage VCCP to GND
15V
Voltage Identification Code Inputs, VID0-VID4
VCCA
Junction Temperature, T
J
150C
Storage Temperature
-65 to 150C
Lead Soldering Temperature, 10 seconds
300C
Power Dissipation, P
D
750mW
Thermal Resistance Junction-to-case,
JC
105C/W
Parameter
Conditions
Min.
Typ.
Max.
Units
Supply Voltage VCCA
4.5
5
5.25
V
Input Logic HIGH
2.0
V
Input Logic LOW
0.8
V
Ambient Operating Temperature
0
70
C
Output Driver Supply, VCCP
11.4
12
13.2
V
RC5057
PRODUCT SPECIFICATION
4
REV. 1.2.0 2/10/00
Electrical Specifications
(V
CCA
= 5V, V
CCP
= 12V, V
OUT
= 2.0V, and T
A
= +25C using circuit in Figure 1,
unless otherwise noted.)
The denotes specifications which apply over the full operating temperature range.
Notes:
1. Steady State Voltage Regulation includes Initial Voltage Setpoint, Droop, Output Ripple and Output Temperature Drift and is
measured at the converter's VFB sense point.
2. As measured at the converter's VFB sense point. For motherboard applications, the PCB layout should exhibit no more than
0.5m
trace resistance between the converter's output capacitors and the CPU. Remote sensing should be used for optimal
performance.
3. Using the VFB pin for remote sensing of the converter's output at the load, the converter will be in compliance with Intel's
VRM 8.4 specification of +50, -80mV. If Intel specifications on maximum plane resistance from the converter's output capac-
itors to the CPU are met, the specification of +40, -70mV at the capacitors will also be met.
4. Includes gate current.
Parameter
Conditions
Min.
Typ.
Max.
Units
Output Voltage
See Table 1
1.3
3.5
V
Output Current
18
A
Initial Voltage Setpoint
I
LOAD
= 0.8A, V
OUT
= 2.400V
V
OUT
= 2.000V
V
OUT
= 1.550V
2.394
2.000
1.550
2.424
2.020
1.565
2.454
2.040
1.580
V
V
V
Output Temperature Drift
T
A
= 0 to 70C, V
OUT
= 2.000V
V
OUT
= 1.550V
+8
+6
mV
mV
Line Regulation
V
CCA
= 4.75V to 5.25V, V
OUT
= 2.000V
2
mV
Internal Droop
3
V
OUT
at I
LOAD
= 0.8A to I
max
-44
-40
-36
mV
Output Ripple
20MHz BW, I
LOAD
= I
max
11
mVpk
Total Output Variation,
Steady State
1
V
OUT
= 2.000V
V
OUT
= 1.550V
3
1.940
1.480
2.070
1.590
V
Total Output Variation,
Transient
2
I
LOAD
= 0.8A to I
max
,V
OUT
= 2.000V
V
OUT
= 1.550V
3
1.900
1.480
2.100
1.590
V
Short Circuit Detect Current
45
60
A
Efficiency
I
LOAD
= I
max
, V
OUT
= 2.0V
85
%
Output Driver Rise & Fall Time
See Figure 4 for t
R
and t
F
50
nsec
Output Driver Deadtime
See Figure 7 for t
DT
50
nsec
Oscillator Frequency
255
300
345
kHz
Duty Cycle
0
100
%
PWRGD Threshold
Logic HIGH
Logic LOW
93
88
107
112
%V
out
V
CCA
UVLO
3.74
4
4.26
V
V
CCP
UVLO
7.65
8.5
9.35
V
V
CCA
Supply Current
19
mA
V
CCP
Supply Current
4
40
mA
Soft Start Current
5
10
17
A
PRODUCT SPECIFICATION
RC5057
REV. 1.2.0 2/10/00
5
Table 1. Output Voltage Programming Codes
Note:
1. 0 = processor pin is tied to GND.
1 = processor pin is open.
VID4
VID3
VID2
VID1
VID0
Nominal V
OUT
0
1
1
1
1
1.30V
0
1
1
1
0
1.35V
0
1
1
0
1
1.40V
0
1
1
0
0
1.45V
0
1
0
1
1
1.50V
0
1
0
1
0
1.55V
0
1
0
0
1
1.60V
0
1
0
0
0
1.65V
0
0
1
1
1
1.70V
0
0
1
1
0
1.75V
0
0
1
0
1
1.80V
0
0
1
0
0
1.85V
0
0
0
1
1
1.90V
0
0
0
1
0
1.95V
0
0
0
0
1
2.00V
0
0
0
0
0
2.05V
1
1
1
1
1
2.0V
1
1
1
1
0
2.1V
1
1
1
0
1
2.2V
1
1
1
0
0
2.3V
1
1
0
1
1
2.4V
1
1
0
1
0
2.5V
1
1
0
0
1
2.6V
1
1
0
0
0
2.7V
1
0
1
1
1
2.8V
1
0
1
1
0
2.9V
1
0
1
0
1
3.0V
1
0
1
0
0
3.1V
1
0
0
1
1
3.2V
1
0
0
1
0
3.3V
1
0
0
0
1
3.4V
1
0
0
0
0
3.5V
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