G5ULM2576 (GTM)
Simple Switcher 3A Step-Down Voltage Regulator

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ISSUED DATE :2005/04/15
REVISED DATE :
G5ULM2576
Simple Switcher 3A Step-Down Voltage Regulator
Description
The G5ULM2576 series of regulators are monolithic integrated circuits that provide all active functions for a step-down (buck) switching
regulator, capable of driving 3A load with excellent line and load regulation. These devices are available in fixed output voltage of 3.3v, 5v,
12v, 15v and an adjustable output version. Requiring a minimum number of external components, these regulators are simple to use and
include internal frequency compensation and a fixed-frequency oscillator.
The G5ULM2576 series offers a high-efficiency replacement for popular three-terminal linear regulators. It substantially reduces the size of
the heat sink, and in some cases no heat sink is required.
A standard series if inductors optimized for use with the G5ULM2576 are available from several different manufactures. This feature
greatly simplifies the design of switch-mode power supplies. Other feature include a guaranteed 4% to tolerance on output voltage within
specified input voltages and output load condition, and 10% on the oscillator frequency. External shutdown is included, featuring 50uA
(typical) standby current. The output switch includes cycle-by-cycle current limiting, as well as thermal shutdown for full protection under
fault condition.
Features
3.3V, 5.0V, 12V, 15V and adjustable output versions
Adjustable version output voltage range , 1.23V to 37V
Guaranteed 3A output current
Wide input voltage range
Efficient pre-regulator for linear regulators
Requires only 4 external components
52kHz fixed frequency oscillator
TTL shutdown capability, low power standby mode
High efficiency
Uses readily available standard inductors
Thermal shutdown and current limit protection
Applications
% max over line and load conditions
Simple high-efficiency step-down (buck) regulator
On-card switching regulators
Positive to negative converter (Buck-Boost)
Package Dimensions
Typical Application (Fixed Output Voltage Version)
G5ULM2576-5.0
REF.
A
b
L4
c
L1
E
Millimeter
Min. Max.
4.40 4.80
0.66 0.91
0.00 0.30
0.36 0.5
2.29 2.79
9.80 10.4
REF.
c2
L2
D
e
L
Millimeter
Min. Max.
1.25 1.45
1.27 REF.
8.6 9.0
1.70 REF.
14.6 15.8
0˚ 8˚
G5ULM2576
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G5ULM2576 (GTM)
Simple Switcher 3A Step-Down Voltage Regulator

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Block Diagram
ISSUED DATE :2005/04/15
REVISED DATE :
3.3V, R2=17k
5.0V, R2=3.1k
12V, R2=8.84k
15V, R2=11.3k
For Adjustable version, R1=open, R2=0
Absolute Maximum Ratings (Note1)
Parameter
Maximum Supply Voltage
ON/OFF pin input Voltage
Output Voltage to ground (steady state)
Power dissipation
Storage Temperature
Maximum junction temperature
Minimum ESD rating (C=100pF, R=1.5k )
Lead temperature (soldering, 10seconds)
Ratings
45
-0.3 V +VIN
-1
Internally Limited
-65 ~ +150
+150
2k
+260
Unit
V
V
V
V
Operating Ratings
Temperature range
Supply Voltage
Parameter
Ratings
-40 TJ +125
40
Unit
V
G5ULM2576-3.3 Electrical Characteristics
Specifications with standard type face are for TJ=25 , and those with boldface type apply over full operating temperature range
Parameter
Symbol
Conditions
Min Typ Max
System Parameters (Note3) Test Circuit Figure 2
Output Voltage
VOUT
VIN=12V, ILOAD=0.5A
Circuit of Figure 2
3.234 3.3 3.366
Output Voltage
VOUT
6V VIN 40V, 0.5A ILOAD 3A
Circuit of Figure 2
3.168/3.135
3.3
3.432/3.465
Efficiency
VIN=12V, ILOAD=3A
75
Unit
V
V
%
G5ULM2576-5.0 Electrical Characteristics
Specifications with standard type face are for TJ=25 , and those with boldface type apply over full operating temperature range
Parameter
Symbol
Conditions
Min Typ Max
System Parameters (Note3) Test Circuit Figure 2
Output Voltage
VOUT
VIN=12V, ILOAD=0.5A
Circuit of Figure 2
4.9 5.0 5.1
Output Voltage
VOUT
8V VIN 40V, 0.5A ILOAD 3A
Circuit of Figure 2
4.80/4.75
5.0
5.20/5.25
Efficiency
VIN=12V, ILOAD=3A
77
Unit
V
V
%
G5ULM2576
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G5ULM2576 (GTM)
Simple Switcher 3A Step-Down Voltage Regulator

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ISSUED DATE :2005/04/15
REVISED DATE :
G5ULM2576-12 Electrical Characteristics
Specifications with standard type face are for TJ=25 , and those with boldface type apply over full operating temperature range
Parameter
Symbol
Conditions
Min Typ Max
System Parameters (Note3) Test Circuit Figure 2
Output Voltage
VOUT
VIN=25V, ILOAD=0.5A
Circuit of Figure 2
11.76 12 12.24
Output Voltage
VOUT
15V VIN 40V, 0.5A
Circuit of Figure 2
ILOAD
3A
11.52/11.40
12
12.48/12.60
Efficiency
VIN=15V, ILOAD=3A
88
Unit
V
V
%
G5ULM2576-15 Electrical Characteristics
Specifications with standard type face are for TJ=25 , and those with boldface type apply over full operating temperature range
Parameter
Symbol
Conditions
Min Typ Max
System Parameters (Note3) Test Circuit Figure 2
Output Voltage
VOUT
VIN=25V, ILOAD=0.5A
Circuit of Figure 2
14.70 15 15.30
Output Voltage
VOUT
18V VIN 40V, 0.5A
Circuit of Figure 2
ILOAD
3A 14.40/14.25
15
15.60/15.75
Efficiency
VIN=18V, ILOAD=3A
88
Unit
V
V
%
G5ULM2576 Electrical Characteristics
Specifications with standard type face are for TJ=25 , and those with boldface type apply over full operating temperature range
Parameter
Symbol
Conditions
Min Typ Max
System Parameters (Note3) Test Circuit Figure 2
Output Voltage
VOUT
VIN=12V, ILOAD=0.5A, VOUT=5V
Circuit of Figure 2
1.217
1.230
1.243
Output Voltage
VOUT
8V VIN 40V, 0.5A ILOAD 3A
VOUT=5V, Circuit of Figure 2
1.193/1.180
1.230
1.267/1.280
Efficiency
VIN=12V, ILOAD=3A, VOUT=5V
77
Unit
V
V
%
All Output Voltage Version Electrical Characteristics
Specifications with standard type face are for TJ=25 , and those with boldface type apply over full operating temperature range.
Unless otherwise specified, VIN=12V for the 3.3V, 5.0V and Adjustable versions, VIN=25V for 12V version, and VIN=30V for 15V version.
ILOAD=0.5A
Parameter
Symbol
Conditions
Min Typ Max Unit
Feedback bias current
Ib VOUT=5V (adjustable version only)
- 50 100/500 nA
Oscillator frequency
fO (Note 8)
47/42
52
58/63
kHz
Saturation voltage
VSAT ILOAD=3A (Note 4)
- 1.4 1.8/2.0 V
Maximum duty cycle
(ON)
DC (Note 5)
93 98
%
Current limit
ICL (Note 4, 8)
4.2/3.5 5.8 6.9/7.5 A
Output leakage current
Quiescent current
Standby quiescent
current
IL
(Note 6, 7) Output=0V
Output=-1V
IQ (Note 6)
ISTBY ON/OFF pin=5V (OFF)
-
-
-
7.5
2
30
mA
- 5 10 mA
- 50 200 uA
ON/OFF Control
ON/OFF pin logic input
level
VIH VOUT=0V
VIL VOUT=Nominal output voltage
2.2/2.4
-
1.4
1.2
-
1.0/0.8
V
ON/OFF pin input
current
IIH ON/OFF pin=5V (OFF)
IIL ON/OFF pin=0V (ON)
- 12 30 uA
- 0 10
G5ULM2576
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G5ULM2576 (GTM)
Simple Switcher 3A Step-Down Voltage Regulator

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ISSUED DATE :2005/04/15
REVISED DATE :
Note 1: Absolute Maximum Rating indicate limits beyond which damage to the device may occur. Operating Rating indicate conditions for
which the device is intended to be functional, but do not guaranteed specific performance limits. For guaranteed specifications and
test conditions, see the Electrical Characteristics.
Note 2: All limits guaranteed at room temperature (standard type face) and at temperature extremes (bold type face).
Note 3: External component such as the catch diode, inductor, input and output capacitors can affect switching regulator system
performance. When the G5ULM2576 is used as shutdown in the Figure 2 test circuit, system performance will be as shown in
system parameters section of Electrical Characteristics.
Note 4: Output pin sourcing current. No diode, inductor or capacitor connected to output.
Note 5: Feedback pin removed from output and connected to 0V.
Note 6: Feedback pin removed from output and connected to +12V for the Adjustable, 3.3V and 5V versions, and +25V for the 12V and
15V versions, to force the output transistor OFF.
Note 7: VIN=40V.
Note 8: The oscillator frequency reduces to approximately 11 kHz in the event of an output short or an overload which causes the
regulated output voltage to drop approximately 40% from the nominal output voltage. This self protection feature lowers the average
power dissipation of the IC by lowering the minimum duty cycle from 5% down to approximately 2%.
Typical Performance Characteristics (circuit of Figure 2)
Normalized Output Voltage
Line Regulator
G5ULM2576
Dropout Voltage
Standby Quiescent Current
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G5ULM2576 (GTM)
Simple Switcher 3A Step-Down Voltage Regulator

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ISSUED DATE :2005/04/15
REVISED DATE :
Quiescent Current
Current Limit
Switch Saturation Voltage
Efficiency
Oscillator Frequency
Minimum Operating voltage
G5ULM2576
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G5ULM2576 (GTM)
Simple Switcher 3A Step-Down Voltage Regulator

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ISSUED DATE :2005/04/15
REVISED DATE :
Quiescent Current vs Duty Cycle
Feedback Voltage vs Duty Cycle
Minimum Power Dissipation
Output
Voltage
Change
Load
Current
Feedback Pin Current
Switching Waveforms
VOUT=15V
A: Output Pin Voltage, 50V/div
B: Output Pin Current, 2A/div
C: Inductor Current, 2A/div
D: Output Ripple Voltage, 50mV/div
AC Coupled
Horizontal Time Base: 5us/div
G5ULM2576
Load Transient Response
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G5ULM2576 (GTM)
Simple Switcher 3A Step-Down Voltage Regulator

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ISSUED DATE :2005/04/15
REVISED DATE :
Test Circuit and layout Guidelines
As in any switching regulator, layout is very important. Rapidly switching currents associated with wiring inductance generate voltage
transients which can cause problems. For minimal inductance and ground loops, the length of the leads indicated by heavy lines should be
kept as short as possible. Single-point grounding (as indicated) or ground plane construction should be used for best results. When using
the Adjustable version, physically locate the programming resistors near the regulator, to keep the sensitive feedback wiring short.
G5ULM2576
Cin-- 100uF, 75V, Aluminum Electrolytic
Cout-- 1000uF, 25V Aluminum Electrolytic
D1-- Schottky, MBR360
L1-- 100uH, Pulse Eng, PE92108
R1-- 2k, 0.1%
R1-- 6.12k, 0.1%
G5ULM2576
Vout=VREF*(1+R2/R1)
R2=R1*(Vout/VREF-1)
Where VREF=1.23V, R1 between 1k and 5k
Figure 2
Important Notice:
All rights are reserved. Reproduction in whole or in part is prohibited without the prior written approval of GTM.
GTM reserves the right to make changes to its products without notice.
GTM semiconductor products are not warranted to be suitable for use in life-support Applications, or systems.
GTM assumes no liability for any consequence of customer product design, infringement of patents, or application assistance.
Head Office And Factory:
Taiwan: No. 17-1 Tatung Rd. Fu Kou Hsin-Chu Industrial Park, Hsin-Chu, Taiwan, R. O. C.
TEL : 886-3-597-7061 FAX : 886-3-597-9220, 597-0785
China: (201203) No.255, Jang-Jiang Tsai-Lueng RD. , Pu-Dung-Hsin District, Shang-Hai City, China
TEL : 86-21-5895-7671 ~ 4 FAX : 86-21-38950165
G5ULM2576
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