ON CS51031 Schematic [ru]

CS51031

Fast P−Ch FET
Buck Controller

The CS51031 is a switching controller for use in DC−DC
converters. It can be used in the buck topology with a minimum
number of external components. The CS51031 consists of a V
monitor for controlling the state of the device, 1.0 A power driver for
controlling the gate of a discrete P−Channel transistor, fixed frequency
oscillator, short circuit protection timer, programmable Soft−Start,
precision reference, fast output voltage monitoring comparator, and
output stage driver logic with latch.

The high frequency oscillator allows the use of small inductors and
output capacitors, minimizing PC board area and systems cost. The
programmable Soft−Start reduces current surges at startup. The short
circuit protection timer significantly reduces the duty cycle to
approximately 1/30 of its cycle during short circuit conditions.

Features

• 1.0 A Totem Pole Output Driver

• High Speed Oscillator (700 kHz max)

• No Stability Compensation Required

• Lossless Short Circuit Protection

• V

Monitor

CC

• 2.0% Precision Reference

• Programmable Soft−Start

• Wide Ambient Temperature Range:

♦ Industrial Grade: −40°C to 85°C
♦ Commercial Grade: 0°C to 70°C

• Pb−Free Packages are Available

5.0 V−12 V

C

IN

47 mF

MP

1

V

GATE

V

GATE

V

C

MBRS360

D

1

IRF7416

CC

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8

1

SOIC−8
D SUFFIX
CASE 751

MARKING DIAGRAM

8

51031

ALYWx

G

1

51031 = Device Code
A = Assembly Location
L = Wafer Lot
Y = Year
W = Work Week
x = Continuation of Device Code

G = Pb−Free Package

x = Y or G

PIN CONNECTIONS

PGND

C

C

OSC

470 pF

© Semiconductor Components Industries, LLC, 2005

October, 2005 − Rev. 11

OSC

GND

Figure 1. Typical Application Diagram

CS

CS51031

V

CC

V

FB

RV

CC

100 W
CV

CC

0.1 mF

R

1.5 kW

A

CS

0.1 mF

R

2.5 kW

C

0.1 mF

1

V

GATE

L

4.7 mH

B

RR

V

O

3.3 V @ 3 A

See detailed ordering and shipping information in the package

C

O

100 mF × 2

1 Publication Order Number:

dimensions section on page 2 of this data sheet.

C

OSC

GND

ORDERING INFORMATION

V

C

CSPGND

V

CC

V

FB

CS51031/D

CS51031

ORDERING INFORMATION

Operating

Device

CS51031YD8
CS51031YD8G SOIC−8

Temperature Range

Package Shipping

SOIC−8 98 Units / Rail

98 Units / Rail

(Pb−Free)
CS51031YDR8 SOIC−8 2500 / Tape & Reel
CS51031YDR8G SOIC−8

−40°C < TA < 85°C

2500 / Tape & Reel

(Pb−Free)
CS51031GD8
CS51031GD8G SOIC−8

CS51031GDR8 SOIC−8 2500 / Tape & Reel

0°C < TA < 70°C

CS51031GDR8G SOIC−8

SOIC−8 98 Units / Rail

98 Units / Rail

(Pb−Free)

2500 / Tape & Reel

(Pb−Free)

†For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging

Specifications Brochure, BRD8011/D.

MAXIMUM RATINGS

Rating Value Unit

Power Supply Voltage, V
Driver Supply Voltage, V
Driver Output Voltage, V
C

, CS, VFB (Logic Pins) 6.0 V

OSC

CC
C
GATE

Peak Output Current 1.0 A
Steady State Output Current 200 mA
Operating Junction Temperature, T
Operating Temperature Range, T
Storage Temperature Range, T

J

A

S

ESD (Human Body Model) 2.0 kV
Lead Temperature Soldering: Wave Solder: (through hole styles only) (Note 1)

Reflow (SMD styles only) (Note 2)

Maximum ratings are those values beyond which device damage can occur. Maximum ratings applied to the device are individual stress limit
values (not normal operating conditions) and are not valid simultaneously. If these limits are exceeded, device functional operation is not implied,
damage may occur and reliability may be affected.

1. 10 sec. maximum.

2. 60 sec. max above 183°C.

20 V
20 V
20 V

150 °C

−40 to 85 °C

−65 to 150 °C

260 peak
230 peak

†

°C
°C

PACKAGE LEAD DESCRIPTION

Package Pin Number Pin Symbol Function

1 V

GATE

Driver pin to gate of external P−Ch FET.
2 PGND Output power stage ground connection.
3 C

OSC

Oscillator frequency programming capacitor.
4 GND Logic ground.
5 V
6 V

FB
CC

Feedback voltage input.

Logic supply voltage.
7 CS Soft−Start and fault timing capacitor.
8 V

C

Driver supply voltage.

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2

CS51031

ELECTRICAL CHARACTERISTICS (Specifications apply for 4.5 ≤ V

≤ 16 V, 3.0 V ≤ VC ≤ 16 V;

CC

Industrial Grade: −40°C < TA < 85°C; −40°C < TJ < 125°C: Commercial Grade: 0 °C < TA < 70°C; 0°C < TJ < 125°C, unless otherwis e specified.)

Characteristic Test Conditions Min Typ Max Unit

Oscillator VFB = 1.2 V

Frequency C
Charge Current 1.4 V < V
Discharge Current 2.7 V > V
Maximum Duty Cycle 1 − (t

Short Circuit Timer

Charge Current 1.0 V < VCS < 2.0 V 175 264 325
Fast Discharge Current 2.55 V > VCS > 2.4 V 40 66 80
Slow Discharge Current 2.4 V > VCS > 1.5 V 4.0 6.0 10

= 470 pF 160 200 240 kHz

OSC

< 2.0 V − 110 −

COSC

> 2.0 V − 660 −

COSC

) 80.0 83.3 − %

OFF/tON

VFB = 1.0 V; CS = 0.1 mF; V

COSC

= 2.0 V

mA
mA

mA
mA
mA

Start Fault Inhibit Time 0 V < VCS < 2.5 V 0.70 0.85 1.40 ms
Valid Fault Time 2.6 V > VCS > 2.4 V 0.2 0.3 0.45 ms
GATE Inhibit Time 2.4 V > VCS > 1.5 V 9.0 15 23 ms
Fault Duty Cycle − 2.5 3.1 4.6 %

CS Comparator VFB = 1.0 V

Fault Enable CS Voltage − − 2.5 − V
Max CS Voltage VFB = 1.5 V − 2.6 − V
Fault Detect Voltage VCS when GATE goes high − 2.4 − V
Fault Inhibit Voltage Minimum V

CS

− 1.5 − V
Hold Off Release Voltage VFB = 0 V 0.4 0.7 1.0 V
Regulator Threshold Voltage Clamp VCS = 1.5 V 0.725 0.866 1.035 V

VFB Comparators V

Regulator Threshold Voltage TJ = 25°C (Note 3)

Fault Threshold Voltage TJ = 25°C (Note 3)

= VCS = 2.0 V

COSC

TJ = −40 to 125°C

TJ = −40 to 125°C

1.225

1.210

1.12

1.10

1.250

1.250

1.15

1.15

1.275

1.290

1.17

1.19

V
V

V

V
Threshold Line Regulation 4.5 V ≤ VCC ≤ 16 V − 6.0 15 mV
Input Bias Current VFB = 0 V − 1.0 4.0

mA
Voltage Tracking (Regulator Threshold − Fault Threshold Voltage) 70 100 120 mV
Input Hysteresis Voltage − − 4.0 20 mV

Power Stage VCC = VC = 10 V; VFB = 1.2 V

GATE DC Low Saturation Voltage V
GATE DC High Saturation Voltage V
Rise Time C
Fall Time C

= 1.0 V; 200 mA Sink − 1.2 1.5 V

COSC

= 2.7 V; 200 mA Source; VC = V

COSC

= 1.0 nF; 1.5 V < V

GATE

= 1.0 nF; 9.0 V > V

GATE

GATE
GATE

GATE

< 9.0 V − 25 60 ns
> 1.5 V − 25 60 ns

− 1.5 2.1 V

VCC Monitor

Turn−On Threshold − 4.200 4.400 4.600 V
Turn−Off Threshold − 4.085 4.300 4.515 V
Hysteresis − 65 130 200 mV

Current Drain

I

CC

I

C

Shutdown I

CC

4.5 V < VCC < 16 V, Gate switching − 4.5 6.0 mA

3.0 V < VC < 16 V, Gate non−switching − 2.7 4.0 mA
VCC = 4.0 − 500 900

mA

3. Guaranteed by design, not 100% tested in production.

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3

CS51031

V

V

REF

RG

I

C

C

OSC

7I

C

+

−

V

CC

V

CC

V

= 3.3 V

REF

I

T

CS

I

T

55

VCCOK

G3

I

T

5

3.3 V

+

−

+

−

+

2.5 V1.5 V

−

V

REF

CS
Comparator

+

A2

−

+

2.5 V1.5 V

−

2.4 V

Oscillator
Comparator

A1

−
A3

+

+

−

G1

G2

Comp

G4

G5

Slow Discharge
Comparator

V

GATE

Flip−Flop

R

F2

S

Hold Off

Comp

−

Fault

1.15 V

+

+

−

R

F1

S

Slow Discharge

Flip−Flop

Q

Q

+

−

Q

Q

A6

0.7 V
+

−

V

FB

Comparator

−

1.25 V

+

CS Charge
Sense
Comparator

A4

+

+

−

+

−

−

2.3 V

C

V

GATE

PGND

V

FB

GND

Figure 2. Block Diagram

CIRCUIT DESCRIPTION

THEORY OF OPERATION

Control Scheme

The CS51031 monitors the output voltage to determine
when to turn on the P−Ch FET. If VFB falls below the internal
reference voltage of 1.25 V during the oscillator’s charge
cycle, the P−Ch FET is turned on and remains on for the

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duration of the charge time. The P−Ch FET gets turned off
and remains off during the oscillator’s discharge time with
the maximum duty cycle to 80%. It requires 7.0 mV typical,
and 20 mV maximum ripple on the VFB pin is required to
operate. This method of control does not require any loop
stability compensation.

4