www.fairchildsemi.com
FAN5035
High Performance Programmable DC-DC Controller
Features
• Programmable output from 1.3V to 3.5V using an
integrated 5-bit DAC
• Remote sense
• 1MHz operation
• 85% efficiency typical at full load
• Integrated Power Good and Enable/Soft Start functions
• Uncommitted Op-amp
• Drives N-channel MOSFETs
• Over-current and over-voltage protection
• 24 pin TSSOP package
Description
The FAN5035 is a voltage-mode DC-DC controller IC
which provides a highly accurate, programmable output
voltage for high-performance processors. The FAN5035
features remote voltage sensing, adjustable current limit and
1MHz operation. The FAN5035 uses a 5-bit D/A converter
to program the output voltage from 1.3V to 3.5V. An
on-board precision low TC reference achieves tight tolerance
voltage regulation without expensive external components.
The FAN5035 also offers integrated functions including
Power Good, Output Enable/Soft Start, current limiting,
over-voltage protection, and an uncommitted op-amp, and is
available in a 24 pin TSSOP package.
Applications
• Power supply for Pentium
®
III
• VRM for Pentium III processor
• Programmable step-down power supply
Block Diagram
+5V
V
IN
14
OVP
OSC
9
V
CC
24
17
16
15
19
A3
20
-
18 +
-
+
-
+
A1
Digital
Control
ISC
-
+
12 OUTA
13
GNDD
7
IFB
6
11
21
5-Bit
DAC
1 2 3 4 5
VID0 VID2 VID4
VID1 VID3
22
OVP
10
OVP
8
VSENSE
23
ENABLE/SS
Power
Good
PWRGD
GNDA
Pentium is a registered trademark of Intel Corporation.
REV. 1.0.0 10/31/01
PRODUCT SPECIFICATION
FAN5035
Pin Assignments
D0
D1
D2
D3
D4
IFB_HI
IFB_LO
VSENSE
V
CC
OVP
PWRGOOD
OUTA
1
2
3
4
5
6
7
8
9
10
11
12
FAN5035
24
23
22
21
20
19
18
17
16
15
14
13
COSC
EN_SS
GNDA
VREF
A3_INN
A3_OUT
A3_INP
A1_OUT
A1_INN
A1_INP
V
IN
GNDD
Pin Definitions
Pin Number
1–5
Pin Name
D0-4
Pin Function Description
Voltage Identification Code Inputs.
These open collector/TTL compatible inputs
will program the output voltage over the ranges specified in Table 1. Pull-up resistors
are internal to the controller.
Current Feedback.
These pins are the input for the current feedback control loop.
Layout of these traces is critical to system performance.
Voltage Sense.
Pin 8 is used as the input for Power Good and over-voltage
protection.
Analog V
CC
.
Connect to system 5V supply and decouple with a 0.1µF ceramic
capacitor.
Over-Voltage Protection.
This pin drives an SCR when the output voltage is too
high.
Power Good Flag.
An open collector output that will be logic LOW if the output
voltage is not within ±10% of the nominal output voltage setpoint.
Output.
Connect this pin to a driver for an N-channel MOSFET. The trace from this
pin to the driver should be <0.5".
Power Ground.
Return pin for high currents flowing in pin 12 (OUTA). Connect to a
low impedance ground.
Input Voltage.
Under-voltage detector input.
Uncommitted Op Amp.
6–7
8
9
10
11
12
13
14
15–17
IFB_HI
IFB_LO
VSENSE
V
CC
OVP
PWRGOOD
OUTA
GNDD
V
IN
A1_INP
A1_INN
A1_OUT
A3_INP
A3_INN
A3_OUT
VREF
GNDA
EN_SS
COSC
18–20
Voltage Feedback Op Amp.
This op amp is used for voltage feedback from the
output, and for loop compensation.
Reference Voltage.
Decouple with a 0.1µF ceramic capacitor.
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.
Output Enable.
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.
Oscillator Capacitor.
Attach a capacitor from pin 24 to ground to set the oscillator
frequency.
21
22
23
24
2
REV. 1.0.0 10/31/01
FAN5035
PRODUCT SPECIFICATION
Absolute Maximum Ratings
Supply Voltage V
CC
All Other Pins
Junction Temperature, T
J
Storage Temperature
Lead Soldering Temperature, 10 seconds
Power Dissipation, P
D
Thermal Resistance Junction-to-case,
Θ
JC
13V
V
CC
150°C
-65 to 150°C
300°C
950mW
16°C/W
Recommended Operating Conditions
Parameter
Supply Voltage V
CC
V
IN
Ambient Operating Temperature
0
Conditions
Min.
4.75
Typ.
5
3.3
70
Max.
5.25
Units
V
V
°C
Electrical Specifications
(V
CC
= 5V, V
OUT
= 2.0V, and T
A
= +25°C using circuit in Figure 1, unless otherwise noted.)
The
•
denotes specifications which apply over the full operating temperature range
Parameter
Voltage Reference
Output Voltage
Voltage Reference Accuracy
Current Feedback
Current Feedback Input Range
IFB Propagation Delay
Oscillator
Oscillator Frequency
Oscillator Frequency Range
Oscillator Frequency TC
Oscillator Duty Cycle
Oscillator Ramp Amplitude
Oscillator Ramp Mean
Output Driver
OUTA Rise Time
OUTA Fall Time
OUTA Voltage Low
OUTA Voltage High
A1 Amplifier
A1 Output Current
A1 Gain-Bandwidth
A1 Open Loop Gain
A1 Slew Rate
REV. 1.0.0 10/31/01
Conditions
See Table I
VID4 = 0
VID4 = 1
•
•
•
•
to OUTA
COSC=47pF
•
•
•
(Voscmax + Voscmin)/2
100pF Load
100pF Load
Isink = 20mA
Isource = 20mA
•
•
•
•
•
•
•
•
•
•
Min.
1.3
-1.2
-1.6
0
180
900
200
Typ.
Max.
3.5
1.2
1.6
V
CC
–0.5
Units
V
%
V
nsec
KHz
KHz
Hz/°C
%
V
PP
V
nsec
nsec
V
V
250
324
1100
1500
328
45
0.75
1.85
0.9
2.05
49
60
V
CC
–1.1
1.7
11
50
10
3
15
55
15
55
1.05
2.25
72
80
0.5
mA
MHz
dB
V/µsec
3
PRODUCT SPECIFICATION
FAN5035
(continued)
(V
CC
= 5V, V
OUT
= 2.0V, and T
A
= +25°C using circuit in Figure 1, unless otherwise noted.)
The
•
denotes specifications which apply over the full operating temperature range
Parameter
A1 Offset Voltage
A1 Input Bias Current
A1 Common Mode Input Range
A1 Output Voltage Swing
A3 Amplifier
A3 Output Current
A3 Gain-Bandwidth
A3 Open Loop Gain
A3 Slew Rate
A3 Offset Voltage
A3 Input Bias Current
A3 Common Mode Input Range
A3 Output Voltage Swing
A3 Input Impedance
VID Lines
D0-4 Pullup to V
CC
D0-4 Logic High
D0-4 Logic Low
Protection
Over-voltage Protection
Over-voltage Hysteresis
Over-voltage Output High
Over-voltage Current
Over-voltage Output Low
Over-voltage Input Impedance
Short Circuit Threshold
Short Circuit Threshold TC
V
IN
Input Impedance
V
IN
UVLO Rising
V
IN
UVLO Falling
V
IN
UVLO Hysteresis
VSENSE Input Inpedance
VSENSE Propagation Delay
VSENSE Propagation Delay
V
CC
UVLO Rising
V
CC
UVLO Falling
V
CC
UVLO Hysteresis
to OVP
to OUTA
Output Low
No Load
VOVP = 3V
VSENSE/VREF
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
4.0
160
250
2.5
160
28
270
250
250
35
350
340
42
442
400
4.5
48
8
72
10
80
12
60
112
1.2
V
CC
–0.2
40
50
0.5
12
88
31
72
3.0
115
3
120
%
%
V
mA
V
KΩ
mV
µV/°C
KΩ
V
V
mV
KΩ
nsec
nsec
V
V
mV
•
•
•
20
2.1
0.8
25
KΩ
V
V
Rload = 2KΩ to 2.5V
INP to Ground
•
•
•
•
•
•
•
•
•
0.25
0.8
9.33
11.67
1.7
11
50
10
3
15
55
15
0.9
340
3
500
V
CC
–0.98
Voscmid + 0.8
14
mA
MHz
dB
V/µsec
mV
nA
V
V
KΩ
Rload = 2KΩ to 2.5V
Conditions
•
•
•
•
-0.1
0.9
Min.
Typ.
0.9
340
Max.
3
500
V
CC
–1.6
V
CC
–0.95
Units
mV
nA
V
V
Electrical Specifications
4
REV. 1.0.0 10/31/01
FAN5035
PRODUCT SPECIFICATION
(continued)
(V
CC
= 5V, V
OUT
= 2.0V, and T
A
= +25°C using circuit in Figure 1, unless otherwise noted.)
The
•
denotes specifications which apply over the full operating temperature range
Parameter
Soft Start/Enable
Soft Start Charge Current
Soft Start Discharge Current
Soft Start Pin Voltage
Power Good
Power Good Output High
Power Good Output Low
Power Good Sink Current
Power Good High Threshold
Power Good Low Threshold
Power Good Threshold Hysteresis
Power Good Propagation Delay
Power Good Rise Time
Power Good Fall Time
V
CC
Supply
V
CC
Supply Current
EN_SS and D0-4 open
D0-4 grounded
During soft-start
•
16
17
22
22
mA
VSENSE to PWRGOOD
10KΩ Pullup
10KΩ Pullup
VPG = 0.4V
VSENSE/VREF
VSENSE/VREF
•
V
CC
– 0.1
•
•
•
•
•
2.0
106
89
1.2
2
60
140
15
2.0
111
94
0.5
V
V
mA
%
%
%
nsec
nsec
nsec
VEN_SS = 1V
•
•
8
-6
20
10
-5
12
-4
80
µA
µA
%V
CC
Conditions
Min.
Typ.
Max.
Units
Electrical Specifications
REV. 1.0.0 10/31/01
5
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