SEMICONDUCTORS
DESCRIPTION
The ZXSC410 is voltage mode boost converter in SOT23-6 package. Its excellent
load and line regulation means that for the full supply range from lithium Ion cells,
the output voltage will typically change by less than 1%. Using high efficiency
Zetex switching transistors allow output voltages of tens of volts depending on the
selected transistor. The ZXSC420 includes a battery low indicator. This operates
by indicating when the converter is no longer able to maintain the regulated
output voltage rather than setting a preset threshold, thereby making it suitable for
various battery options and load currents.
FEATURES
•1.65V to 8V supply range
•Typical output regulation of ±1%
•Over 85% typical efficiency
•Output currents up to 300mA
•4.5A typical shutdown current ZXSC410
•End of regulation output ZXSC420
APPLICATIONS
•System power for battery portable products
•LCD bias
•Local voltage conversion
DEVICE MARKING
•C410 ZXSC410
•C420 ZXSC420
ZXSC410
ZXSC420
ISSUE 2 - May 2003
1
VOLTAGE MODE BOOST CONVERTER
DEVICE REEL
SIZE TAPE
WIDTH QUANTITY
PER REEL
ZXSC410E6TA 7” 8mm 3000 units
ZXSC420E6TA 7” 8mm 3000 units
ORDERING INFORMATION
SOT23-6
V
CC
GND
SENSE
DRIVE
STDN
V
FB
U1
ZXSC410
Q1
FMMT617
C2
D1
ZHCS1000
L1
C1
R2
R3R1
V
IN
V
OUT
TYPICAL APPLICATIONS DIAGRAM
ABSOLUTE MAXIMUM RATINGS
VCC -0.3V to +10V
DRIVE -0.3V to VCC + 0.3V
EOR -0.3V to VCC + 0.3V * (ZXSC420 only)
STDN -0.3V to The lower of (+5.0V) or (VCC + 0.3V) * (ZXSC410 only)
VFB, SENSE -0.3V to The lower of (+5.0V) or (VCC + 0.3V)
Operating Temp. -40°C to +85°C
Storage Temp. -55°C to +125°C
Power Dissipation 450mW
ZXSC410
ZXSC420
SEMICONDUCTORS
ISSUE 2 - May 2003
2
Symbol Parameter Conditions Limits Units
Min Typ Max
Supply parameters
VCC VCC Range 1.8 8 V
Iq1Quiescent Current VCC = 8V 220 A
ISTDN Shutdown Current 4.5 A
Eff2Efficiency 50mA > IOUT > 300mA 85 %
AccREF Reference tolerance 1.8V < VCC < 8V -3.0 3.0 %
TCOREF Reference Temp Co 0.005 %/⬚C
TDRV Discharge pulse width 1.8V < VCC < 8V 1.7 s
FOSC Operating Frequency 200 kHz
Input parameters
VSENSE sense voltage 22 28 34 mV
ISENSE sense input current VFB=0V;VSENSE=0V -1 -7 -15 A
VFB Feedback voltage TA=25°C 291 300 309 mV
IFB2Feedback input current VFB=0V;VSENSE=0V -1.2 -4.5 A
VIH Shutdown high voltage 1.5 1 VCC V
VIL Shutdown low voltage 0 0.55 V
dVLN Line voltage regulation 0.5 %/V
Output parameters
IOUT3Output current VIN >2V,V
OUT =V
IN 300 mA
IDRIVE Transistor drive current VDRIVE = 0.7V 2 3.4 5 mA
VDRIVE Transistor voltage drive 1.8V < VCC <8V 0 V
CC-0.4 V
CDRIVE Mosfet gate drive cpbty 300 pF
VOHEOR EOR Flag output high IEOR = -300nA 2.5 VCC V
VOLEOR EOR Flag output low IEOR = 1mA 0 1.15 V
TEOR EOR delay time TA=25°C 70 195 250 s
dILD Load current regulation 0.01 %mA
ELECTRICAL CHARACTERISTICS
Test Conditions VCC= 3V, T= -40°C to 85°C unless otherwise stated.
Note
1Excluding gate/base drive current.
2IFB is typically half of these values at 3V
3System not device spec, including recommended transistors.
TYPICAL CHARACTERISTICS
ZXSC410
ZXSC420
SEMICONDUCTORS
ISSUE 2 - May 2003
3
DEVICE DESCRIPTION
Bandgap Reference
All threshold voltages and internal currents are derived
from a temperature compensated bandgap reference
circuit with a reference voltage of 1.22V nominal.
Dynamic Drive Output
Depending on the input signal, the output is either
“LOW”or “HIGH”. In the high state a 2.5mA current
source (max drive voltage = VCC-0.4V) drives the base
or gate of the external transistor. In order to operate the
external switching transistor at optimum efficiency,
both output states are initiated with a short transient
current in order to quickly discharge the base or the
gate of the switching transistor.
Switching Circuit
The switching circuit consists of two comparators,
Comp1 and Comp2, a gate U1, a monostable and the
drive output. Normally the DRIVE output is “HIGH”; the
external switching transistor is turned on. Current
ramps up in the inductor, the switching transistor and
external current sensing resistor. This voltage is
sensed by comparator, Comp2, at input ISENSE. Once
the current sense voltage across the sensing resistor
exceeds 20mV, comparator Comp2 through gate U1
triggers a re-triggerable monostable and turns off the
output drive stage for 2µs. The inductor discharges to
the load of the application. After 2µs a new charge cycle
begins, thus ramping the output voltage. When the
output voltage reaches the nominal value and VFB gets
an input voltage of more than 300mV, the monostable
is forced “on”from Comp1 through gate U1, until the
feedback voltage falls below 300mV. The above action
continues to maintain regulation.
EOR, End of Regulation Detector
The EOR circuit is a retriggerable 120µs monostable,
which is re-triggered by every down regulating action
of comparator Comp1. As long as regulation takes
place, output EOR is “HIGH“(high impedance, 100K to
VCC). Short dips of the output voltage of less than
120µs are ignored. If the output voltage falls below the
nominal value for more than 120µs, output EOR goes
”LOW“. The reason for this to happen is usually a
slowly progressing drop of input voltage from the
discharging battery. Therefore the output voltage will
also start to drop slowly. With the EOR detector,
batteries can be used to the ultimate end of discharge,
with enough time left for a safe shutdown.
Block Diagrams
ZXSC410
ZXSC420
SEMICONDUCTORS
ISSUE 2 - May 2003
4
+
_
+
_
R2
R3
R1
STDN
VCC
DRIVE
SENSEGND V
FB
Shutdown Bandgap
Reference Bias Generator
Comp 1
Comp 2
U1
Dynamic
Drive
Monostable
2µs
Fig. 1 ZXSC410
Fig. 1 ZXSC420
APPLICATIONS INFORMATION
Switching transistor selection
The choice of switching transistor has a major impact
on the converter efficiency. For optimum performance,
a bipolar transistor with low VCE(SAT) and high gain is
required. The VCEO of the switching transistor is also an
important parameter as this sees the full output
voltage when the transistor is switched off. Zetex
SuperSOT™transistors are an ideal choice for this
application.
Schottky diode selection
As with the switching transistor, the Schottky rectifier
diode has a major impact on the converter efficiency. A
Schottky diode with a low forward voltage and fast
recovery time should be used for this application.
The diode should be selected so that the maximum
forward current rating is greater or equal to the
maximum peak current in the inductor, and the
maximum reverse voltage is greater or equal to the
output voltage. The Zetex ZHCS Series meet these
needs.
Combination devices
To minimise the external component count Zetex
recommends the ZX3CDBS1M832 combination of
NPN transistor and Schottky diode in a 3mm x 2mm
MLP package. This device is recommended for use in
space critical applications.
The IC is also capable of driving MOSFETs. Zetex
recommends the ZXMNS3BM832 combination of low
threshold voltage N-Channel MOSFET and Schottky
diode in a 3mm x 2mm MLP package. This device is
recommended for use in space critical applications.
Inductor Selection
The inductor value must be chosen to satisfy
performance, cost and size requirements of the overall
solution.
Inductor selection has a significant impact on the
converter performance. For applications where
efficiency is critical, an inductor with a series resistance
of 500m⍀or less should be used.
A list of recommended inductors is listed in the table
below:
Peak current definition
In general, the IPK value must be chosen to ensure that
the switching transistor, Q1, is in full saturation with
maximum output power conditions, assuming
worse-case input voltage and transistor gain under all
operating temperature extremes.
Once IPK is decided the value of RSENSE can be
determined by:
RSENSE
V
SENSE
IPK
=
ZXSC410
ZXSC420
SEMICONDUCTORS
ISSUE 2 - May 2003
5
Pin No. Name Description
1V
CC Supply voltage, 1.8V to 8V.
2 GND Ground
3 STDN/EOR Shutdown ZXSC410 / End of regulation ZXSC420
4 SENSE Inductor current sense input. Internal threshold voltage set to
28mV. Connect external sense resistor.
5V
FB Reference voltage. Internal threshold set to 300mV. Connect
external resistor network to set output voltage.
6 DRIVE Drive output for external switching transistor. Connect to base or
gate of external switching transistor.
Part No. Manufacture L IPK
(A) RDC
( )
CMD4D11-100MC Sumida 10µH 0.5 0.457
CMD4D11-220MC Sumida 22µH 0.4 0.676
LPO2506OB-103 Coilcraft 10µH 1.0 0.24
ST2006103 Standex
Electronics Inc
10µH 0.6 0.1
PIN DESCRIPTIONS
Sense Resistor
A low value sense resistor is required to set the peak
current. Power in this resistor is negligible due to the
low sense voltage threshold, VSENSE. Below is a table
of recommended sense resistors:
Output power calculation
By making the above assumptions for inductance and
peak current the output power can be determined by:
POUT = IAV x VIN x= (Watts)
where
II
2X(T T
(T T
AV
PK ON DIS
ON OFF
=+
+
)
)
and
TIxL
V
ON
PK
IN
=
and
TIxL
V-V
DIS
PK
OUT IN
=
and
TOFF ≅1.7µs (internally set by ZXSC410)
and
= efficiency i.e. 100% = 1
Operating frequency can be derived by:
F1
TT
ON OFF
=+
Output capacitors
Output capacitors are a critical choice in the overall
performance of the solution. They are required to filter
the output and supply load transient currents. There
are three parameters which are paramount in the
selection of the output capacitors, capacitance, IRIPPLE
and ESR. The capacitance value is selected to meet the
load transient requirements. The capacitors IRIPPLE
rating must meet or exceed the current ripple of the
solution.
The ESR of the output capacitor can also affect loop
stability and transient performance. The capacitors
selected for the solutions, and indicated in the
reference designs, are optimised to provide the best
overall performance.
Input capacitors
The input capacitor is chosen for its voltage and RMS
current rating. The use of low ESR electrolitic or
tantalum capacitors is recommended. Capacitor
values for optimum performance are suggested in the
reference design section
Also note that the ESR of the input capcitor is
effectively in series with the input and hence
contributes to efficiency losses in the order of IRMS2.
ESR.
ZXSC410
ZXSC420
SEMICONDUCTORS
ISSUE 2 - May 2003
6
Manufacture Series RDC(⍀)
Range Size Tolerance URL
Cyntec RL1220 0.022 - 10 0805 ±5% http://www.cyntec.com
IRC LR1206 0.010 - 1.0 1206 ±5% http://www.ictt.com
Output voltage adjustment
The ZXSC410/420 are adjustable output converters
allowing the end user the maximum flexibilty. For
adjustable operation a potential divider network is
connected as follows:
The output voltage is determined by the equation:
VV1
RA
RB
OUT FB
=+
where VFB=300mV
The resistor values, RA and RB, should be maximised
to improve efficiency and decrease battery drain.
Optimisation can be achieved by providing a minimum
current of IFB(MAX)=200nA to the VFB pin. Output is
adjustable from VFB to the (BR)VCEO of the switching
transistor, Q1.
Note: For the reference designs, RA is assigned the
label R2 and RB the label R3.
Layout issues
Layout is critical for the circuit to function in the most
efficient manner in terms of electrical efficiency,
thermal considerations and noise.
For ‘step-up converters’there are four main current
loops, the input loop, power-switch loop, rectifier loop
and output loop. The supply charging the input
capacitor forms the input loop. The power-switch loop
is defined when Q1 is ‘on’, current flows from the input
through the inductor, Q1, RSENSE and to ground. When
Q1 is ‘off’, the energy stored in the inductor is
transferred to the output capacitor and load via D1,
forming the rectifier loop. The output loop is formed by
the output capacitor supplying the load when Q1 is
switched back off.
To optimise for best performance each of these loops
kept separate from each other and interconnected with
short, thick traces thus minimising parasitic
inductance, capacitance and resistance. Also the
RSENSE resistor should be connected, with minimum
trace length, between emitter lead of Q1 and ground,
again minimising stray parasitics.
ZXSC410
ZXSC420
SEMICONDUCTORS
ISSUE 2 - May 2003
7
RB
VFB
GND
VOUT
RA
STDN
GND
V
CC
DRIVE
SENSE
V
FB
EOR
GND
V
CC
DRIVE
SENSE
V
FB
ZXSC410
SOT23-6 ZXSC420
SOT23-6
CONNECTION DIAGRAMS
ZXSC410
ZXSC420
SEMICONDUCTORS
ISSUE 2 - May 2003
8
Ref Value Part Number Manufacture Comments
U1 ZXSC410E6 Zetex DC-DC converter IC
U2 ZX3CDBS1M832 Zetex Low sat NPN + 1A Schottky
L1 22µH CMD4D11-220 Sumida 1mm height profile
R1 100mΩLR1206 / RL1220 IRC / Cyntec 1206 / 0805 size
R2 16kΩGeneric Generic 0603 size
R3 1kΩGeneric Generic 0603 size
C1 22µF/6V3 GRM Series Murata 1206 size
C2 22µF/6V3 GRM Series Murata 1206 size
C3 1nF Generic Generic 0603 size
REFERENCE DESIGNS
ZXSC410 DC-DC Controller
VIN=2.5V to 4.2V
VOUT=5V; ILOAD=100mA
Bill of Materials
ZXSC410
ZXSC420
SEMICONDUCTORS
ISSUE 2 - May 2003
9
V=1V/DIV; T=10µS/DIV
Switching Waveform V=50mV/DIV; T=10µS/DIV
Output Ripple
Performance Graphs
ZXSC410
ZXSC420
SEMICONDUCTORS
ISSUE 2 - May 2003
10
AVDD=9V/180mA
VON=18V/10mA
VOFF=9V/10mA
AVDD=9V/180mA
VON=27V/10mA
VOFF=9V/10mA
ZXSC410 as Triple Output TFT Bias
ZXSC410 as Triple Output TFT Bias
ZXSC410
ZXSC420
SEMICONDUCTORS
ISSUE 2 - May 2003
11
Sequencing AVDD and VON
ByaddingthecircuitbelowtotheLCDbiasoutput (VON)of
the converter a 10ms delay can be achieved between
AVDD powerup andVON power up.The circuitoperates by
a delay in turning the PMOS transistor on, which transfers
to a 10ms delay between input and output of the circuit.
The delay is set by the RC time constant of R1 and C1.
The diode, D1, discharges the gate of the PMOS when
the main system supply is turned off, guaranteeing a
delay every turn on cycle.
ZXSC410
ZXSC420
SEMICONDUCTORS
12
ISSUE 2 - May 2003
Europe
Zetex plc
Fields New Road
Chadderton
Oldham, OL9 8NP
United Kingdom
Telephone (44) 161 622 4444
Fax: (44) 161 622 4446
hq@zetex.com
Zetex GmbH
Streitfeldstraße19
D-81673 München
Germany
Telefon: (49) 89 45 49 49 0
Fax: (49) 89 45 49 49 49
europe.sales@zetex.com
Americas
Zetex Inc
700 Veterans Memorial Hwy
Hauppauge, NY 11788
USA
Telephone: (1) 631 360 2222
Fax: (1) 631 360 8222
usa.sales@zetex.com
Asia Pacific
Zetex (Asia) Ltd
3701-04 Metroplaza Tower 1
Hing Fong Road
Kwai Fong
Hong Kong
Telephone: (852) 26100 611
Fax: (852) 24250 494
asia.sales@zetex.com
These offices are supported by agents and distributors in major countries world-wide.
This publication is issued to provide outline information only which (unless agreed by the Company in writing) may not be used, applied or reproduced
for any purpose or form part of any order or contract or be regarded as a representation relating to the products or services concerned. The Company
reserves the right to alter without notice the specification, design, price or conditions of supply of any product or service.
For the latest product information, log on to www.zetex.com
© Zetex plc 2003
DIM
Millimetres Inches
DIM
Millimetres Inches
Min Max Min Max Min Max Min Max
A 0.90 1.45 0.35 0.057 E 2.60 3.00 0.102 0.118
A1 0.00 0.15 0 0.006 E1 1.50 1.75 0.059 0.069
A2 0.90 1.30 0.035 0.051 L 0.10 0.60 0.004 0.002
b 0.35 0.50 0.014 0.019 e 0.95 REF 0.037 REF
C 0.09 0.20 0.0035 0.008 e1 1.90 REF 0.074 REF
D 2.80 3.00 0.110 0.118 L 0°10°0°10°
PACKAGE DIMENSIONS
CONTROLLING DIMENSIONS IN MILLIMETRES APPROX CONVERSIONS INCHES.
A1
2
L
DATUM A
a
C
E
AA2
E1
D
be
e1
PACKAGE OUTLINE PAD LAYOUT DETAILS
