ISL6252HRZ Intersil, ISL6252HRZ Datasheet - Page 18

• Manufacturer Part Number: ISL6252HRZ
• Description: IC BATTERY CHARGER CTRLR 28-QFN
• Manufacturer: Intersil

Specifications of ISL6252HRZ

• Function: Charge Management
• Battery Type: Lithium-Ion (Li-Ion), Lithium-Polymer (Li-Pol)
• Voltage - Supply: 7 V ~ 25 V
• Operating Temperature: -10°C ~ 100°C
• Mounting Type: Surface Mount
• Package / Case: 28-VFQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

estimated by operating at very low load current (100mA) and
measuring the ringing frequency.
CSNUB and RSNUB can be calculated from Equations 26
and 27:
Input Capacitor Selection
The input capacitor absorbs the ripple current from the
synchronous buck converter, which is given by Equation 28:
This RMS ripple current must be smaller than the rated RMS
current in the capacitor datasheet. Non-tantalum chemistries
(ceramic, aluminum, or OSCON) are preferred due to their
resistance to power-up surge currents when the AC adapter
is plugged into the battery charger. For Notebook battery
charger applications, it is recommended that ceramic
capacitors or polymer capacitors from Sanyo be used due to
their small size and reasonable cost.
Table 2 shows the component lists for the typical application
circuit in Figure 2.
C
R
I
RMS
C
C
SNUB
SNUB
C
PARTS
2
3
Q
, C
, C
1
C
1
Q
C
C
D
D
R
R
R
R
R
R
, C
L
, Q
11
=
4
7
5
6
1
2
6
1
2
3
4
5
6
, C
, C
10
=
=
2
I
BAT
8
9
------------------------------------ -
(
2πF
------------------- -
C
------------------------------------------------------------ -
10µF/25V ceramic capacitor, Taiyo Yuden
TMK325 MJ106MY X5R (3.2mmx2.5mmx1.9mm)
0.1µF/50V ceramic capacitor
1µF/10V ceramic capacitor, Taiyo Yuden
LMK212BJ105MG
10nF ceramic capacitor
6.8nF ceramic capacitor
3300pF ceramic capacitor
30V/3A Schottky diode, EC31QS03L (optional)
100mA/30V Schottky Diode, Central Semiconductor
10µH/3.8A/26mΩ, Sumida, CDRH104R-100
30V/35mΩ, FDS6912A, Fairchild
Signal N-Channel MOSFET, 2N7002
40mΩ, ±1%, LRC-LR2512-01-R040-F, IRC
20mΩ, ±1%, LRC-LR2010-01-R020-F, IRC
18Ω, ±5%, (0805)
2.2Ω, ±5%, (0805)
100kΩ, ±5%, (0805)
4.7k, ±5%, (0805)
2 L
SNUB
V
ring
⋅
TABLE 2. COMPONENT LIST
OUT
2
PART NUMBERS AND MANUFACTURER
)
2
⋅
⋅
(
L
V
V
IN
IN
–
V
18
OUT
)
ISL6252, ISL6252A
(EQ. 26)
(EQ. 27)
(EQ. 28)
Loop Compensation Design
ISL6252 has three closed loop control modes. One controls
the output voltage when the battery is fully charged or
absent. A second controls the current into the battery when
charging and the third limits current drawn from the adapter.
The charge current and input current control loops are
compensated by a single capacitor on the ICOMP pin. The
voltage control loop is compensated by a network on the
VCOMP pin. Descriptions of these control loops and
guidelines for selecting compensation components will be
given in the following sections. Which loop controls the
output is determined by the minimum current buffer and the
minimum voltage buffer shown in Figure 1. These three
loops will be described separately.
TRANSCONDUCTANCE AMPLIFIERS GM1, GM2 AND
GM3
The ISL6252 uses several transconductance amplifiers (also
known as gm amps). Most commercially available op amps
are voltage controlled voltage sources with gain expressed
as A = V
controlled current sources with gain expressed as
gm = I
some of the equations for poles and zeros in the
compensation.
PWM GAIN F
The Pulse Width Modulator in the ISL6252 converts voltage
at VCOMP to a duty cycle by comparing VCOMP to a
triangle wave (duty = VCOMP/V
filter formed by L and C
output voltage (Vo = V
wave amplitude is proportional to V
amplitude proportional to DCIN makes the gain from
VCOMP to the PHASE output a constant 11 and is
independent of DCIN. For small signal AC analysis, the
battery is modeled by it’s internal resistance. The total output
resistance is the sum of the sense resistor and the internal
resistance of the MOSFETs, inductor and capacitor.
Figure 18 shows the small signal model of the pulse width
modulator (PWM), power stage, output filter and battery.
PARTS
R
8
R
R
R
R
R
, R
10
12
13
OUT
7
9
11
OUT
TABLE 2. COMPONENT LIST (Continued)
/V
IN
/V
100Ω, ±5%, (0805)
130k, ±1%, (0805)
10.2kΩ, ±1%, (0805)
4.7Ω, ±5%, (0805)
20kΩ, ±1%, (0805)
1.87kΩ, ±1%, (0805)
M
. Transconductance gain (gm) will appear in
IN
. Transconductance amps are voltage
PART NUMBERS AND MANUFACTURER
DCIN
O
convert the duty cycle to a DC
*duty). In ISL6252, the triangle
P-P RAMP
DCIN
. Making the ramp
). The low-pass
August 25, 2010
FN6498.3