MOTOROLA MC1121DMR2 Datasheet

MC1121

100mA Charge Pump V oltage
Converter with Shutdown

The MC1121 is a charge pump converter with 100mA output
current capability. It converts a 2.4V to 5.5V input to a corresponding
negative output voltage. As with all charge pump converters, the
MC1121 uses no inductors saving cost, size, and reducing EMI.

An on–board oscillator operates at a typical frequency of 10kHz (at
VDD = 5V) when the frequency control input (FC) is connected to
ground. The oscillator frequency increases to 200kHz when FC is
connected to VDD, allowing the use of smaller capacitors. Operation at
sub–10kHz frequencies results in lower quiescent current and is
accomplished with the addition of an external capacitor from OSC (pin

7) to ground. The MC1121 can be driven from an external clock
connected OSC. Typical supply current at 10kHz is 50µA, and falls to
less than 1µA when the shutdown input is brought low, whether the
internal or an external clock is used. The MC1121 is available in a
Micro–8 package.

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Micro8

DM SUFFIX

CASE TBD

PRELIMINARY INFORMATION

Features

• Converts a 2.4V to 5.5V Input Voltage to a Corresponding Negative

Output Voltage (Inverter Mode)

• Uses Only 2 Capacitors; No Inductors Required!

• High Output Current: 100mA

• Selectable Oscillator Frequency: 10kHz to 200kHz

• Power–Saving Shutdown Input

• Optional High–Frequency Operation Allows Use of Small Capacitors

• Low Operating Current (FC = GND): 50µA

• T ested Operating Temperature Range: –40°C to +85°C

Typical Applications

• Laptop Computers

• Medical Instruments

• Disk Drives

• µP–Based Controllers

• Process Instrumentation

FUNCTIONAL BLOCK DIAGRAM

+

–

CAP

–

V

out

C2

+

SHDN

FC

OSC

V

DD

GND

OSC

CONTROL

MC1121

CAP

RC

OSCILLATOR

LOGIC

CIRCUITS

+

C1

SWITCH

MATRIX

PIN CONFIGURATION

(Top View)

FC

1

CAP+

2
3
4

MC1121

GND

CAP–

ORDERING INFORMATION

Device Package Shipping

MC1121DMR2 Micro–8 2500 Tape/Reel

8
7
6
5

V

DD

OSC
SHDN
V

OUT

 Semiconductor Components Industries, LLC, 1999

February , 2000 – Rev. 0

1 Publication Order Number:

MC1121/D

MC1121

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PIN DESCRIPTION

Pin No. Symbol Description

1

ÁÁÁ

2
3
4
5
6
7

8

ABSOLUTE MAXIMUM RATINGS*

VDD Supply Voltage 6.0 V
Operating Temperature Range –40 to +85 °C
OSC, FC, SHDN Input Voltage –0.3 to (VDD + 0.3) V
Output Short Circuit Duration 10 Sec
Storage Temperature Range –65 to +150 °C
Package Power Dissipation (TA ≤ 70°C) Micro8

Derate by 4mW/°C for TA > 70°C

Lead Temperature (Soldering, 10 Seconds) +300 °C

* Maximum Ratings are those values beyond which damage to the device may occur.

FC

ÁÁÁÁ

CAP+

GND
CAP–
V

OUT

SHDN

OSC

V

DD

Frequency control for internal oscillator, FC = open, F
typ, FC has no effect when OSC pin is driven externally

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= 10kHz typ; FC = VDD, F

OSC

OSC

Charge–pump capacitor, positive terminal
Power–supply ground input
Charge–pump capacitor, negative terminal
Output, negative voltage
Shutdown
Oscillator control input. An external capacitor can be added to slow the oscillator. Take care to

minimize stray capacitance. An external oscillator also may be connected to overdrive OSC
Power–supply positive voltage input

Parameter Value Unit

333

= 200kHz

mW

ELECTRICAL CHARACTERISTICS (TA = –40°C to +85°C, VDD = 5V ±10% C

= OPEN, C1, C2 = 10µF, FC = VDD,

OSC

SHDN = VIH, unless otherwise noted. Typical values are at TA = 25°C.)

Symbol Characteristic Min Typ Max Unit

I

DD

I

DD(SHDN)

V

DD

V

IH

V

IL

I

IN

R

OUT

I

OUT

F

OSC

P

EFF

V

EFF

Active Supply Current

RL = Open, FC = Open or GND
RL = Open, FC = V

DD

—
—

50

0.6

100

1.0

Shutdown Supply Current (SHDN = 0V) — 0.2 1.0 µA
Supply Voltage 2.4 — 5.5 V
SHDN Logic High Input Voltage VDD x 0.8 — — V
SHDN Logic Low Input Voltage — — 0.4 V
Input Leakage Current

SHDN

, OSC

FC Pin
Output Source Resistance (I
Output Current (V

more negative than –3.75V) 60 100 — mA

OUT

–1.0
–4.0

= 60 mA) — 12 20

OUT

—
—

1.0

4.0

Oscillator Frequency

OSC Open, FC = Open or GND

= VIH, FC = V

SHDN

DD

5.0

100

10

200

—
—

Power Efficiency (FC = GND)

RL = 2kW between VDD and V

RL = 1 kW between V

IL = 60 mA to GND

OUT

and GND

OUT

93
94
—

97
97
92

—
—
—

Voltage Conversion Efficiency (RL = OPEN) 99 99.9 — %

µA

mA

µA

W

kHz

%

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2

MC1121

APPLICATIONS INFORMATION

Negative Voltage Converter

The MC1121 is typically used as a charge–pump voltage
inverter. C1 and C2 are the only two external capacitors used
in the operating circuit (see Figure 1).

2.4 V to 5.5 V

MC1121

+

SHDN

–

V

DD

OSC

V

out

7

SHDN*

6

V

5

–
+

out

C2

+

C2

–

NOTES: *SHDN

Figure 1. Charge Pump Inverter

FC

18

CAP

2

GND

3

CAP

4

should be tied to VDD if not used.

The MC1121 is not actively regulated. A typical output
source resistance of 11.8W means that an input of +5V
results in - 5V output voltage under light load, and only
decreases to - 3.8V (typ) with a 100mA load.

The supplied output current is from capacitor C2 during
one–half the charge–pump cycle. This results in a
peak–to–peak ripple of:

V

RIPPLE

Where f

= I

is 5kHz (one half the nominal 10kHz

PUMP

OUT

/2(f

PUMP

) (C2) + I

OUT

(ESRC2)

oscillator frequency), and C2 = 150µF with an ESR of 0.2
ripple is about 90mV with a 100mA load current. If C2 is
raised to 390µF, the ripple drops to 45mV.

Changing Oscillator Frequency

The MC1121’s clock frequency is controlled by four
modes:

The oscillator runs at 10kHz (typical) when FC and OSC
are not connected. The oscillator frequency is lowered by
connecting a capacitor between OSC and GND, but FC can
still multiply the frequency by 20 times in this mode.

An external clock source that swings within 100mV of
VDD and GND may overdrive OSC in the inverter mode.
OSC can be driven by any CMOS logic output. When OSC
is overdriven, FC has no effect.

Note that the frequency of the signal appearing at CAP

+

and CAP- is half that of the oscillator. In addition, by
lowering the oscillator frequency, the effective output
resistance of the charge–pump increases. T o compensate for
this, the value of the charge–pump capacitors may be
increased.

Because the 5kHz output ripple frequency may be low
enough to interfere with other circuitry, the oscillator
frequency can be increased with the use of the FC pin or an
external oscillator. The output ripple frequency is half the
selected oscillator frequency. Although the MC1121’s
quiescent current will increase if the clock frequency is
increased, it allows smaller capacitance values to be used for
C1 and C2.

Capacitor Selection

In addition to load current, the following factors affect the
MC1121 output voltage drop from its ideal value 1) output
resistance, 2) pump (C1) and reservoir (C2) capacitor ESRs,
and 3) C1 and C2 capacitance.

The voltage drop is the load current times the output
resistance. The loss in C2 is the load current times C2’ s ESR;
C1’s loss is larger because it handles currents greater than
the load current during charge–pump operation. Therefore,

W

the voltage drop due to C1 is about four times C1’s ESR
multiplied by the load current, and a low (or high) ESR
capacitor has a greater impact on performance for C1 than
for C2.

In general, as the MC1121’s pump frequency increases,
capacitance values needed to maintain comparable ripple
and output resistance diminish proportionately.

FC OSC Oscillator Frequency

Open Open 10kHz
FC = V
Open or

FC = V
Open External Clock External Clock Frequency

Open 200kHz

DD

External
Capacitor

DD

Reduced from 10kHz or
200kHz depending on FC state

Cascading Devices

To produce greater negative magnitudes of the initial
supply voltage, the MC1121 may be cascaded (see Figure 2).
The resulting output resistance is approximately equal to the
sum of individual MC1121 R
(where n is an integer representing the number of devices
cascaded) is defined by
V

OUT

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3

= - n (VIN).

values. The output voltage

OUT