MIC3809YM Micrel Inc, MIC3809YM Datasheet - Page 2

• Manufacturer Part Number: MIC3809YM
• Description: Push-Pull DC/DC Controller ( )
• Manufacturer: Micrel Inc

Specifications of MIC3809YM

• Lead Free Status: Lead free
• Pwm Type: Current Mode
• Number Of Outputs: 1
• Frequency - Max: 1MHz
• Duty Cycle: 50%
• Voltage - Supply: 2 V ~ 14 V
• Buck: Yes
• Boost: No
• Flyback: No
• Inverting: No
• Doubler: No
• Divider: No
• Cuk: No
• Isolated: Yes
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 8-SOIC (3.9mm Width)
• Frequency-max: 1MHz
• Other names: 576-1770-5; MIC3809YM

MIC3808/3809
Ordering Information
Pin Configuration
Pin Description
MIC3808/3809
Pin Number
Standard
MIC3808BM
MIC3809BM
MIC3808BMM
MIC3809BMM
1
2
3
4
Part Number
MIC3808YMM
MIC3809YMM
MIC3808YM
MIC3809YM
Lead-Free
Pin Name
COMP
CS
RC
FB
COMP
Threshold
RC
CS
FB
Turn On
12.5V
12.5V
4.3V
4.3V
Pin Function
COMP is the output of the error amplifier and the input of the PWM com-
parator. The error amplifier in the MIC3808 is a true low-output impedance,
4MHz operational amplifier. As such, the COMP pin can both source and
sink current. However, the error amplifier is internally current limited, so that
zero duty cycle can be externally forced by pulling COMP to GND. The
MIC3808 family features built-in full cycle soft start. Soft start is imple-
mented as a clamp on the maximum COMP voltage.
The inverting input to the error amplifier. For best stability, keep FB lead
length as short as possible and FB stray capacitance as small as possible.
The input to the PWM, peak current, and overcurrent comparators. The
overcurrent comparator is only intended for fault sensing. Exceeding the
overcurrent threshold will cause a soft start cycle. An internal MOSFET
discharges the current sense filter capacitor to improve dynamic perfor-
mance of the power converter.
The oscillator programming pin. The MIC3808’s oscillator tracks V
GND internally, so that variations in power supply rails minimally affect
frequency stability. Only two components are required to program the
oscillator, a resistor (tied to the V
and GND). The approximate oscillator frequency is determined by the simple
formula:
where frequency is in Hertz, resistance in Ohms, and capacitance in Farads.
The recommended range of timing resistors is between 7kΩ and 200kΩ and
range of timing capacitors is between 100pF and 1000pF. Timing resistors
less than 7kΩ should be avoided. For best performance, keep the timing
capacitor lead to GND as short as possible, the timing resistor lead from V
as short as possible, and the leads between timing components and RC as
short as possible. Separate ground and V
network are encouraged.
1
2
3
4
MSOP-8 (MM)
SOIC-8 (M)
2
Threshold
Turn Off
8.3V
4.1V
8.3V
4.1V
F
OSCILLATOR
8 VDD
7
6
5
OUTA
OUTB
GND
Temperature Range
=
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
DD
1.41
RC
and RC), and a capacitor (tied to the RC
DD
traces to the external timing
8-Pin MSOP
8-Pin MSOP
8-Pin SOIC
8-Pin SOIC
Package
DD
April 2005
and
Micrel
DD